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									Introduction to Psychology

PSYCHOLOGY- is derived from the Greek words psyche which means ―soul‖ and logos which
means ―the study of ―. It is a scientific study of mental processes and behavior.

    Scientific study- it is a scientific discipline because its principles were based on the
         combination of the sp-called super sciences (scientific fields) such as medicine, biology
         and philosophy.
    Mental processes and behavior- involve the processes of reasoning, emotion, motivation and
         learning. Psychology also purports to explain how do human beings think and relate with
         each other. It also studies how the human brain works and the variables which affect its
    The discipline also covers the study of nonhuman organisms (from single-called
         microorganisms to gigantic mammals.
    Scientific study of how the body functions and sociology (systematic study of the relationship
         between man and the whole society.
    It can be regarded as a natural science and a social science.


Ancient Greece and Rome (600-300 BC)
     HIPPOCRATES- claimed that the body and the mind are separate entities. This theory is
        now called as the mind-body dualism. MIND-BODY DUALISM ―philosophical belief
        that the mind is qualitatively different from the body.
     PLATO-he supported the latter theory that the mind reside within the brain.
             1. Plato’s View on the Nature of Reality.-Reality can be found in the ideal and not
                 in the objects that are recognized by our senses. (material and tangible objects).
             2. Aristotle’s View on the Nature of Reality-Aristotle’s philosophical standpoint is
                 the direct opposite of Plato’s view. Reality rests upon the concrete and tangible
                 objects. He argued that it is impossible for the mind (or soul) to exist without the
                 presence of the body.
Early Modern Period
     RENE DESCARTES- believed that human knowledge and absolute facts could only be
        attained through rational processes instead of empirical method. He also subscribed to the
        Hippocratic idea that the mind and the body are two separate and distinct entities(theory
        of mind-body dualism).
     JOHN LOCKE- believed that initially, human mind can be similarly compared to a
        ―blank slate (tabula rasa).He believed that man is naturally good (optimistic view on
        human nature).
     IMMANUEL KANT- Accdg. to him, both rationalist and empiricist approach are
        essential to understand complex mental processes. He reconciled the issue between
        monism and dualism.
             MONISM- the fusion of mind and body, thus, these separate entities would
                 eventually become one.
    A scholarly discipline
    A scientific field of study
    An applied Profession
Psychology: Natural Science or Social Science- psychology as a science deals with the laws of
nature. As a social science comes in the discipline when it attempts to explain a particular
psychological phenomenon through the use of social relations, individual behavior, role and
importance of family and etc.

    Cognitive psychology- is the study of thinking. This field has something to do with the
        intellectual domain of a person. It also tends to develop a man’s ability to learn, perceive
        and think with regard to specific information.
    Psychobiology- the biological domain of psychology. It is also termed as biological/
        physiological. psycho biologists are more focused on the biological foundations of
        psychology such as the study of cells, brain, sense of organs and etc.
    Social Psychology- the social domain of psychology. It also attempts to explain how man
        interacts with the general society.
    Developmental Psychology- this field focuses on the stages of human development. It
        usually tackles the processes of maturation and learning.
    Neuropsychology-a psychological field which is confined in the study of the nervous system.
        People who study neuropsychology are focused on the biological bases of motivation,
        memory, perception, sensation and learning.
    Clinical psychology- it provides treatments/solutions to various types of abnormal behavior
        and mental disorders.
    Forensic psychology- it is the application of psychological theories within the legal the legal
    Health psychology- it refers to the relationship between the mental and physical health of the
    School of psychology-it applies psychological theories to diagnose and explain the
        behavioral and mental irregularities of the students.
    Engineering psychology- this field is concerned with the technological relationship of
        humans and industrial machines.
    Organizational psychology- this field purports to explain vital factors within a specific
    Educational psychology-psychological theories are being used to develop effective teaching
        strategies and comprehensive curricula.
    Cultural psychology- this field of psychology attempts to study diverse/multiple culture to
        various parts of the world. Ethnicity and culture affect human behavior.
    Positive Psychology-this field only deals with the desirable qualities/attributes of man such
        as happiness, positive human experience, contentment, hope and etc.
    Political psychology-social psychology theories are related to political issues which explain
        the behavior of political factors.


EMPIRICISM- the term has Latin and Greek translations namely experentia and empeiria or
English language ―experience‖.
    According to empiricists human knowledge can be attained in two ways: first is through
        the use of human senses and the second through introspective awareness, that is by,
        experience. JOHN LOCKE is one of the proponents of empiricists who argued that the
        mind can be compared to a ―blank state‖ (tabula rasa)
    Nativisim –refers to the belief that man is already conscious with the reality. This belief
        does not consider human senses as one of the important elements to fully understand the
        nature of reality. RENE DISCARTES is the 17th century philosopher and mathematician
     who viewed that selected ideas(infinity, existence of God, mathematical operations etc)
     are innate to human mind.
ACHIEVEMENTS in the Field in Psychology

   Wilhelm Wundt(1879) is considered as the father of scientific psychology.
   Hermann Ebbinghaus (1885) He conducted the 1st experiment on memory.
   William James (1890) He was the author of the monumental scholastic literature in the
     history of psychology the ―Principles of Psychology‖
   Edward Thorndlike (1898) his experiments were focused on the behavioral approach
     wherein he emphasized the role of law of effect that serves as the basis for operant
   Sigmund freud (1900) He was the author of the book entitled ―The interpretation of
     Dreams‖. He is also the FATHER OF PSYCHOLOGY.
   Alfred Binet/Theopile Simon (1905) Developed the first I. Q exam which was introduced
     in French public schools.
   STRUCTURALISM- grew out of the work of James, Wundt, and their associates. These
     psychologists believed the chief purpose of psychology was to describe, analyse, and
     explain conscious experience, particularly feelings and sensations. The structuralists
     attempted to give a scientific analysis of conscious experience by breaking it down into
     its specific components or structures. For example, they identified four basic skin
     sensations: warmth, cold, pain, and pressure. They analyzed the sensation of wetness as
     the combined experience of cold and smoothness.
   GESTALT PSYCHOLOGY, like behaviorism, developed as a reaction against
     structuralism. Gestalt psychologists believed that human beings and other animals
     perceive the external world as an organized pattern, not as individual sensations. For
     example, a film consists of thousands of individual still pictures, but we see what looks
     like smooth, continuous movement. The German word Gestalt means pattern, form, or
     shape. Unlike the behaviorists, the Gestaltists believed that behaviour should be studied
     as an organized pattern rather than as separate incidents of stimulus and response. The
     familiar saying "The whole is greater than the sum of its parts" expresses an important
     principle of the Gestalt movement.

    FUNCTIONALISM- According to functionalism the subject matter of psychology is
     mental processes or in other words, ―functions‖. Functionalism was a protest against
     structuralism.    Structuralism was the study of the contents of consciousness.
     Functionalism was utilitarian and concerned with commonsense issues. Structuralists
     said that mental functions were not subject to introspective analysis, it was the make up
     of the mind that could be analyzed. Functionalists disagreed, saying they could study
     mental function if correct methods were used. There were many men responsible for the
     development of functionalism. Here are just a few important contributors.

      Psychodynamics- this approach is based on the Freudian conceptual model.
       Moreover, it asserts that powerful unconscious urges control behavior. Underlying
       the actions of people are the basic and instinctive motivations rooted on man’s sexual
       and aggressive instincts.
      Evolutionary- this perspective views that the existing behavior is the product of the
       selection process which started several million years ago. It means that the process
       brought developmental changes to the present organisms and their behavior.
         Behaviorism- this kind of approach is more focused along the model of stimulus-
             response and negative –positive reinforcements in trying to account human
             behavior.In addition, behavior is learned as man adapts to his environment.
         Humanistic view- this approach is posited their conception of psychology along the
             terms of human experiences as well as development of man’s full potential. It views
             man accdg. to his innate capacity and motivation for fulfillment and achievement
             towards desired future and goals.
         Cognitive perspective-it focuses on how the mind processes knowledge and
             information in day-to-day living. Man is capable of rational thinking (has the
             capacity to reason) and therefore his behavior can be considered as a product of how
             man processes a particular information.
         Biological perspective- this approach states that behavior has physiological and
             neurological basis. This perspective gives importance to man’s biological being as
             determinant of behavior that could be viewed as a product of biological and chemical
             activities in the body and the nervous system.
         Socio-cultural perspective- this perspective asserts that the individual could be best
             understood if his historical, social and cultural backgrounds are factored in.
         Behavioral genetics perspective- this psychological perspective claims that the results
             formed by the interaction between genes and environment influences human
Human behavior is the collection of behaviors exhibited by human beings and influenced by
culture, attitudes, emotions, values, ethics, authority, rapport, hypnosis, persuasion, coercion
and/or genetics.

               Human behavior is so unpredictable. Perhaps it is this quality of behavior that
                clouds the fact that there are set emotions that we feel on particular situations.
               Objective dimension of behavior refers to the set emotions that every human
                being is tuned to feel irrespective of one’s race or culture, like the joy that every
                individual feels on succeeding in some endeavor.
               The subjective dimension is attributed in the mind. The human mind is complex
                and individualistic that makes accurate prediction of individual behavior a big
               The fact still remains that it is the mind that decides the individuality of each
                person as far as human behavior psychology is concerned and how does it do that
                needs to be understood.

Factors affecting human behavior

Drives and Motives: Instincts are defined as the innate biological forces like fear, aggression,
curiosity and reproduction that decide human behavior. Instincts that are fixed from birth but can
be changed as per learning and experience.Aside from inner driving forces, there were external
factors that played an equally important role in setting the direction of human behavior.

Factors affecting human behavior

Social norms: Society conditions our behavior by the process of socialization in which an
individual picks up attitudes and norms of the society by being exposed to them.
Genetics: Behavioral genetics is the branch of science that tries to find the role of genetics behind
human behavior psychology.
It is most widely accepted that genetics alone cannot explain human behavior. Most psychologists
today believe that behavior is the result of complex interplay between genetics and behavior.
Hormones: They are known to affect the development of cognitive capabilities and also the
nervous system. Our cognitive abilities and development of nervous system both play an
important role in how an individual perceives a particular situation and reacts to it.
Hormones being secreted in excess or deficient amounts are known to cause behavioral and
personality disorders as well as the hyperactivity of thyroid glands.

Endocrine System – consist of a group of glands that produces regulatory of chemicals called
hormones. The endocrine system and the nervous system work together to control and coordinate
all other system of the body. The nervous system controls such rapid activity as muscle
movement and intestinal activity by means of electrical and chemical stimuli.
The connection between the nervous system and the endocrine system enable endocrine function
to adjust to the demands of a changing environment.

    Gland – refers to an organ that is specialized to produce a substance that is sent out to other
       parts of the body. There are 2 types of glands:

           Exocrine Glands – presence of ducts or tubes to carry secretions away from the
            gland. The secretions may be carried to another organ, to a body activity or to the
            body surface.
           Endocrine Glands – these are ductless glands that secrete substances called
            hormones that have specific effects on other tissues.

    o   Functions of the Endocrine System

        The endocrine system functions with the nervous system to regulate the many activities
        critical to the maintenance of homeostasis.

             Water Balance – it regulates water balance by controlling the solute
              concentration of the blood.
             Uterine Contractions and Milk Release – it regulates uterine contractions
              during delivery and stimulates milk release from the breasts n lactating females.
             Growth, Metabolism and Tissue Maturation – it regulates the growth of
              tissues, such as bone and muscle, and the rate of metabolism of most tissues,
              which helps maintain a normal body temperature and normal functions.
             Ion Regulation – it regulates sodium, potassium and calcium ion concentrations
              in the blood.
             Heart Rate and Blood Pressure Regulation – it helps regulate the heart rate
              and blood pressure and helps prepare the body for physical activity.
             Blood Glucose Control – it regulates blood glucose levels abd other nutrient
              levels in the blood.
             Immune System regulation – it helps control the production of immune cells.
             Reproductive Functions and Control – it controls the development and
              function of the reproductive system in males and females.

    o   Body Hormones

             The term comes from the Greek term which means to ―to set in motion‖.
              Hormones serve as transmitters of information from one cell to another. Fluids
               that are secreted by endocrine glands. In addition, these body substances perform
               a significant role in sexual growth development.

Major Endocrine Glands

The endocrine system consists of ductless glands, which secrete hormones directly into the
circulatory system. The endocrine glands are supplied by an extensive network of blood vessels;
organs with the richest blood supply include endocrine glands such as the adrenal and thyroid

   o   Pituitary Gland

       The pituitary gland, or hypophysis, is a small gland about the size of a pea.
       It rests in a depression of the sphenoid bone inferior to the hypothalamus of the brain.
       The hypothalamus is an important autonomic nervous system and endocrine control
       center of the brain located inferior to the thalamus. The pituitary gland is located
       posterior to the optic chiasma and is connected to the hypothalamus by a stalk caked the

       The pituitary gland was historically referred to as the master gland of the body because it
       controls the functions of so many other glands.

       Within the hypothalamus and pituitary, the nervous and endocrine systems are closely
       interrelated. Emotions such as joy and anger, as well as chronic stress, influence the
       endocrine system through the hypothalamus. Conversely, hormones of the endocrine
       system can influence the functions of the hypothalamus and other parts of the brain.

            Hormones of Adenohypophysis

                      Adrenocorticotropic Hormone – molecules bind to membrane-bound
                       receptors of cells in the cortex of the adrenal glands. This hormone also
                       increases the section of a hormone from the adrenal cortex called cortisol
                       and ACTH is required to keep the adrenal cortex from degenerating
                       ACTH molecules also bind to melanocytes in the skins and increase skin
                      Growth Hormone – stimulates the growth of the bones, muscles, and
                       other organs by increasing protein synthesis. It also resists protein
                       breakdown during periods of food deprivation and favors fat breakdown.
                       Gonadotropic Hormones – hormones that bind to membrane-bound
                       receptors on the cells of the gonads (ovaries and testes). They regulate
                       the growth d, development, and functions of the gonads.
                      Thyroid-Stimulating Hormone – molecules bind to membrane-bound
                       receptors on cells of the thyroid gland and cause the cells to secrete
                       thyroid hormone.
                      Prolactin Hormone – molecules bind to membrane-bound receptors in
                       cells of the breast and help promote development of the breast during
                       pregnancy and stimulate the production of milk in the breast following
         Hormones of Neurohypophysis

                   Antidiuretic Hormone – molecules bind to membrane-bound receptors
                    and increase water re-absorption by kidney tubules. These results in less
                    water lost as urine.
                   Oxytocin - molecules bind to membrane-bound receptors and cause
                    contraction of the muscle and uterus and milk ejection, or milk ―let-
                    down‖, from the breasts in the lactating women.

o   Pineal Gland

    It is a small cone-shaped structure located superior and posterior to the thalamus of the
    brain. Melatonin is the hormone produced by the pineal body.

o   Parathyroid Glands

    The tiny parathyroid glands are embedded in the posterior wall of the thyroid gland.
    Typically, there are two glands on each thyroid lobe; that is a total of four, but as many as
    eight have been reported and some may be in other regions of the neck.

         Parathyroid Hormone or Parathormone – it is the most important regulator of
          calcium ion homeostasis in the blood. Although calcitonin has a role in
          regulating blood calcium levels, PTH is more important than calcitonin in
          regulating blood calcium levels of calcium.

o   Adrenal Glands (Suprarenal Glands)

    These are two small glands that are located superior to each kidney. Each adrenal gland
    has an inner part, called the adrenal medulla, and an outer, called the adrenal cortex.
    The adrenal medulla and the adrenal cortex function as separate endocrine glands.

         Hormoned of Adrenal Medulla

                   Epinephine (adrenaline) and small amount of Norepinephrine are
                    released from the adrenal medulla in response to stimulation by the
                    sympathetic nervous system which becomes active when a person is
                    physically active. Some major effects of the hormones released from the
                    adrenal medulla are:

                   Increase in the breakdown of glycogen to glucose in the liver, the
                   release of the glucose into the blood, and the release of fatty acids
                   from the fat cells.
                Increase in the heart rate, which cause the blood pressure to increase.
                Stimulation of smooth muscle in the walls of arteries supplying the
                   internal organs and the skin but not those supplying skeletal muscle.
                Increase in blood pressure because of smooth muscle contraction in
                   the walls of blood vessels in the internal organs and skin.
                Increase in the metabolic rate of several tissues, especially skeletal
                   muscle, cardiac muscles and nervous tissue.
         Hormones of the Adrenal Cortex
                  Mineralcorticoids – help regulate blood volume and blood levels of
                   potassium and sodium ions. Aldosterone is the major hormone of this
                   class. Aldosterone molecules bind to receptor molecules primarily in the
                   kidney, but it also affects the intestine, sweat glands, and salivary glands.
                  Glucocorticods – help regulate blood mutrient levels in the body. The
                   major glucocorticod hormone is cortisol, which increases the breakdown
                   of protein and fat and increases their conversion to forms that can be
                   used as energy sources by the body.
                  Gonadocorticoids (Sex Hormones)

                      Androgen - a type of adrenal hormone which has the ability to
                       stimulate the development of male characteristics. In adult males,
                       most androgens are secreted by the testes. In a adult females, the
                       adrenal androgens influence the female sex drive.

o   Pancreas Islets (Islets of Langerhans)

    These are dispersed among the exocrine portion of the pancreas. The islets secrete two
    hormones namely: insulin and glucagons. These hormones help regulate blood nutrient

        Hormones of the Pancreatic Islets

                  Insulin - it is released from the beta cells primarily in response to
                   elevated blood glucose levels and increased parasympathetic stimulation
                   that is associated with digestion of a meal.
                  Glucagon - it is released from the alpha cells when blood glucose levels
                   are low.

o   Gonads (Sex Glands)

    The female and male gonads produce sex hormones that are identical to those produced
    by adrenal cortex cells. The major differences are the source and relative amounts
         Hormones of the Ovaries

              Female Gonads – these are paired, almond-sized organs located in the pelvic
               cavity> Besides producing female sex cells (ova, or eggs).

        Hormones of the Testes

              Male Gonads - the paired oval testes of the male are suspended in the
                    Testosterone - it originates from the interstitial cells of the testes.
   o   Other Endocrine Glands

           Thymus Gland – it is located in the upper thorax, posterior to the sternum.
           Gastric Mucusa - it is placed within the lining of the stomach. This gland also
            produces hormone called gastrin.
           Mucosa of the Small Intestine – this gland produces secretin and cholecystokinin.

                 Secretin – it helps the pancreas to release a bicarbonate-rich fluid to equalize
                  the excessive amount of acid in the stomach.
                 Cholecystokinin – it helps the gall bladder to contract in order to release bile.
                  This fluid helps the pancreas to produce an enzyme needed for the digestion.
                 Atria – these are cells which are situated in the wall of the upper chambers of
                  the heart.
                 Placenta – this serves as a temporary endocrine gland for pregnant females.

The Nervous System

   o   Functions of the Nervous System

           Sensory Output – sensory receptors are always on the look-out for the external
            and internal stimuli, such as touch, temperature, taste, smell, sound, blood
            pressure and body position.
           Integration – the brain and spinal cord process input and initiates responses. The
            input may produce an immediate reaction, may be stored as memory, or may be
        Homeostasis – it is the ability of the nervous system to detect, interpret and
         respond to changes in the internal and external environment.
        Mental Activity – the brain is the center of intellectual activity, including
         consciousness, memory and thinking.
        Control of Skeletal Muscles – the nervous system controls major movements of
         the body since skeletal muscles normally contract only when stimulated by the
         nervous system.

o Two Divisions of the Nervous System

        Central Nervous System (CNS) – it consists of the brain and the spinal cord.
         The brain and spinal cord occupy the dorsal body cavity and act as the integrating
         and command centers of the nervous system.
        Peripheral Nervous System (PNS) – it consists of nerves and ganglia which lie
         outside. The nerves serve as communicating lines.

o   Parts of the Brain

        Brain – part of the CNS housed within the cranial vault. The brain consists of the
         brainstream, diencephalons cerebrum, and cerebellum.

        Brainstream – made up of the medulla, the pons and the midbrain. The
         brainstream connects the spinal cord to the remainder of the brain and contains
         several nuclei involved in body functions such as control of heart rate and
               Medulla Oblongata - is the most inferior portion of the brainstream
                and is continuous with the spinal cord.

 The pyramid consists of descending nerve tracts, which transmit action potentials
  from the brain to motor neurons of the spinal cord and are involved in the
  conscious control of skeletal muscles.

               Pons – the term means ―bridge‖ and it describes both function and
                structure of the pons.

               Midbrain – it is the smallest region of the brainstream. The superior
                part of the midbrain consists of four mounds called colliculi.

 Diencephalons – part of the brain between the brainstream and the cerebrum. Its
  main components are the following.

           Thalamus - the thalamus is by far the largest part of the diencephalons.
            It consists of a cluster of nuclei and is shaped somewhat like a yo-yo,
            with two large, lateral parts connected to the center by a small
            intermediate mass.

           Pineal Body – an endocrine gland that may influence the onset of
            puberty. It also plays a significant role in controlling some long-term
            cycles that are influenced by the light-dark cycle.

         Hypothalamus - the most inferior of the diencephalon and contains
          several small nuclei which are essential in maintaining homeostasis.

 Cerebrum - it is the largest part of the brain. It is divided into the right and left
  hemisphere by a longitudinal fissure. The right cerebral hemisphere controls
  muscular activities and receives input from the left half of the body. The left
  cerebral hemisphere controls muscles and receives input from the right half of the

           Functions of the Cerebral Cortex

            Impulses are received and analyzed within the cerebral cortex, the layer
            of gray matter that forms the surface of each cerebral hemisphere.
            Although the various areas of the brain act in coordination to produce
            behavior, particular functions are localized in the cortex of each lobe.
            Some of these are described below:

           Frontal Lobe – it is relatively larger in humans than in any other
            organisms. It lies in front of the central sulcus.

           Parietal Lobe – it occupies the upper part of each hemisphere and lies
            just behind the central sulcus.
                       Temporal Lobe – it lies below the lateral sulcus and folds under the
                        hemisphere on each side.

                       Occiptal Lobe – it lies behind the parietal lobe and extends over the

Cerebellum - it is a Latin word which means ―little brain‖. It primarily involves sensory
perception and motor output.

Motor, Sensory, Association Areas and Processing Areas of the Cerebral Cortex

The following areas are located within the previously discussed lobes of the cerebral cortex.

    o   Motor and Sensory Areas

             Primary Motor Area- located in the frontal lobe of the brain.

             Primary Somatosensory Area – unlike the primary motor area, the primary
              somatosensory area is located in the parietal lobe which is apparently just across
              the frontal lobe.

             Primary Taste Area – this area is responsible for taste sensations.

             Primary Visual Area – it is located in the occipital lobe, which is at the extreme
              side of the brain.

             Primary Auditory Area – the auditory area is located in the temporal lobe.

    o   Association Areas – needed in order to integrate tasks performed by both association,
        motor and sensory areas.

             Premotor Area – located before the primary motor area which arranges motor

             Somatosensory Association Area – it is located at the rear side of the primary
              somatosensory area.

             Visual Association Area – it is in anterior to the primary visual area.

             Auditory Association Area – it links and analyzes and processes the newly
              received auditory information to the newly transmitted auditory information with
              previously received auditory information.

    o   Processing Areas
         Prefontal Area – it accepts, analyzed and processes the transmitted information from
          the different areas of the brain.

         Broca’s Area (motor speech) – this area controls the muscles related to speech.

         Wirnecke’s Area (sensory speech area) – also called as the general interpretative
          area in which the previously transmitted and received information are interpreted
          through speech.

The peripheral nervous nervous system is composed of all the neuron cell bodies and processes
located outside the brain and the spinal cord. The PNS can be classified into two parts: 12 pairs of
cranial nerves and 31 pairs of spinal nerves.

Cranial Nerves
   o The 12 pairs of cranial nerve s primarily serve the head and neck.

             12 Pairs of cranial nerves:

                       Olfactory

                       Optic

                       Oculomotor

                       Trochelear
                      Trigeminal

                      Abducens

                      Facial

                      Vestibulocochlear

                      Glosso-pharyn-geal

                      Vagus

                      Accessory

                      Hypoglossal

Somatic Nervous System
   o The SNS is responsible for the quick movements exerted by our skeletal muscles.

   o   Two types of nerves present in the somatic nervous system:

            Afferent Nerves – information produced by sense organs and muscles are
             carried by these nerves to the CNS

            Efferent Nerves – information produced by the CNS are carried by these nerves
             to muscles and sense organs

Autonomic Nervous System
   o The autonomic nervous system is the motor subdivision of the PNS that controls
      activities automatically.

Two Arms of the Autonomic Nervous System
  o Sympathetic Division

       The sympathetic division is also called the thoracolumbar division because its first
       neurons are in the gray matter of the spinal cord from T1 through T2.

   o   Parasympathetic Divison

       The parasympathetic motor pathways begin in the craniosacral areas, with fibers arising
       from the cell bodies in the brainstream and the lower part of the spinal cord.

   o The nervous system is composed of two kinds of cells; the glial cell is to support the
      main structure of the nervous system.

            Glial cells support the main structure of the nervous system;

            Remove waste products;
             Maintain the neuron’s survival by nurturing it; and

             Protect the nervous system

    o   Neurons receive stimuli and transmit action potentials to other neurons or to effector

Two Categories of Neurons (Shape and Direction)

Neurons can be classified into two categories; according to their shapes and according to the
direction that they send information.

    o   According to their shapes:

             Multipolar – it is composed of several deadrites and an axon.

             Bipolar – composed of one dendrite and one axon. It can be found in special
              sense organs such as the eye and the nose.

             Unipolar – a neuron with a single axon. It can be considered as the most afferent

    o   According to the directions:

             Motor Neurons - commonly unknown as the afferent neurons which transport
              information away fromm the spinal cord and the brain to the muscles and
              different body parts.

             Sensory Neurons - these are called efferent neuronswhich transmit information
              from the sensory parts of the body.

             Interneurons – link the motor and sensory neorons


Sensation - refers to the process of sensing our environment through touch, taste, sight, sound,
and smell. Is the process by which our senses gather information in raw form and send it to the
brain, where perception comes into play.

Perception - is the way we interpret these sensations and therefore make sense of everything
around us. Is the process of attaining awareness or understanding of sensory information. The
word "perception" comes from the Latin words perceptio, percipio, and means "receiving,
collecting, action of taking possession, apprehension with the mind or senses. Is one of the oldest
fields in psychology. The oldest quantitative law in psychology is the Weber-Fechner law, which
quantifies the relationship between the intensity of physical stimuli and their perceptual effects.


Sight or vision is the ability of the brain and eye to detect electromagnetic waves within the
visible range (light) which is why people see interpreting the image as "sight." Neuroanatomists
generally regard it as two senses, given that different receptors are responsible for the perception
of color (the frequency of photons of light) and brightness (amplitude/intensity - number of
photons of light). Some argue that stereopsis, the perception of depth, also constitutes a sense, but
it is generally regarded as a cognitive (that is, post-sensory) function of brain to interpret sensory
input and to derive new information. The inability to see is called blindness.


Hearing or audition is the sense of sound perception. Since sound is vibrations propagating
through a medium such as air, the detection of these vibrations, that is the sense of the hearing, is
a mechanical sense akin to a sense of touch, albeit a very specialized one. In humans, this
perception is executed by tiny hair fibres in the inner ear which detect the motion of a membrane
which vibrates in response to changes in the pressure exerted by atmospheric particles within a
range of 20 to 22000 Hertz, with substantial variation between individuals. Sound can also be
detected as vibrations conducted through the body by tactition. The inability to hear is called


Taste or gustation is one of the two main "chemical" senses. There are at least four types of
―tastes buds" (receptors) on the tongue detect, and hence there are anatomists who argue that
these constitute five or more different senses,

given that each receptor conveys information to a slightly different region of the brain. The
inability to taste is called ageusia.


Smell or olfaction is the other "chemical" sense. Unlike taste, there are hundreds of olfactory
receptors, each binding to a particular molecular feature. Odor molecules possess a variety of
features and thus excite specific receptors more or less strongly. This combination of excitatory
signals from different receptors makes up what we perceive as the molecule's smell. In the brain,
olfaction is processed by the olfactory system. Olfactory receptor neurons in the nose differ from
most other neurons in that they die and regenerate on a regular basis. The inability to smell is
called anosmia.


Touch, also called tactition or mechanoreception, is a perception resulting from activation of
neural receptors, generally in the skin including hair follicles, but also in the tongue, throat, and
mucosa. A variety of pressure receptors respond to variations in pressure (firm, brushing,
sustained, etc). The touch sense of itching caused by insect bites or allergies involves special itch-
specific neurons in the skin and spinal cord. The loss or impairment of the ability to feel anything
touched is called tactile anesthesia. Paresthesia is a sensation of tingling, pricking, or numbness
of the skin that may result from nerve damage and may be permanent or temporary.

Sense of sight

The eye - is a complex organ composed of many parts. It acts like a video camera. Everything
you look at was sent to your brain for processing and storage much like a video cassette. The
sense of sight is considered the most complex of the five senses.

How you’re Eyes Work?

Take a moment to locate an object around you. Do you know how you are able to see it? Would
you believe that what you are actually seeing are beams of light bouncing off of the object and
into your eyes? It is hard to believe, but it is true. The light rays enter the eye through the cornea,
which is a thick, transparent protective layer on the surface of your eye. Then the light rays pass
through the pupil (the dark circle in the center of your eye) and into the lens.

When light rays pass through your pupil, the muscle called the iris (colored ring) makes the size
of the pupil change depending on the amount of light that's available. You may have noticed this
with your own eye if you have looked at it closely in a mirror. If there is too much light, your
pupil will shrink to limit the number of light rays that enter. Likewise, if there is very little light
available, the pupil will enlarge to let in as many light rays as it can.

Just behind the pupil is the lens and it focuses the image through a jelly-like substance called the
vitreous humor onto the back surface of the eyeball, called the retina.

The retina, which is the size of your thumbnail, is filled with approximately 150 million light-
sensitive cells called rods and cones. Rods identify shapes and work best in dim light. Cones on
the other hand, identify color and work best in bright light. Both of these types of cells then send
the information to the brain by way of the optic nerve. It is the brain's job to turn the image
rightside up and then tell you what you are looking at. The brain does this in a specific place
called the visual cortex.

The eyebrows are the strips of hair above your eyes which prevent sweat from running into them.
Eyelashes help keep the eye clean by collecting small dirt and dust particles floating through the
air. The eyelashes also protect the eye from the sun's and other light's glare. The eyelids sweep
dirt from the surface of the eye. The eyelid also protects the eye from injury. Tears are sterile
drops of clean water which constantly bathe the front of the eye, keeping it clean and moist.

   Most people blink every 2-10 seconds.
    If you only had one eye, everything would appear two-dimensional.
    Owls can see a mouse moving over 150 feet away with light no brighter than a candle.
    One in every twelve males is color blind.

    I.   Six extrinsic muscles attach the eye to the bony socket:

                    inferior rectus;
                   medial rectus;
                   superior rectus;
                   lateral rectus;
                   inferior oblique;
                   superior oblique.

The four rectus muscles move the eye up and down and from side to side. The two oblique
muscles rotate the eye.

The lacrimal system - (tear ducts) produce tears to clean, moisten and lubricate the eyes and then
drains the excess fluid into the nose.

                                                      Antomy of the eye

                                                         II. Eyeball
                                                              - A hallow, fluid-filled sphere
                                                                  which has a larger posterior
                                                                  compartment. It makes up about
                                                                  5/6 of the eye as compared to
                                                                  the much smaller anterior
                                                                  compartment which makes of
                                                                  1/6 of the eye.
                                                      Three layers (tunics of the eye
     a. Fibrous Tunic
                Consisting of the sclera behind and the cornea in front. The sclera is opaque,
                and constitutes the posterior five-sixths of the tunic; the cornea is transparent,
                and forms the anterior sixth.
                The Sclera.—the sclera has received its name from its extreme density and
                hardness; it is a firm, unyielding membrane, serving to maintain the form of the
                bulb. It is much thicker behind than in front; the thickness of its posterior part is
                1 mm. Its external surface is of white color, and is in contact with the inner
                surface of the fascia of the bulb.
                The Cornea.— is the projecting transparent part of the external tunic, and forms
                the anterior sixth of the surface of the bulb. It permits the light to enter the eye.

     b. Vascular Tunic
                The vascular tunic of the eye is formed from behind forward by the choroid, the
                ciliary body, and the iris. It is the middle Tunic of eye. The layer which contains
                most of the blood vessels.
                The Choroid (chorioidea).—The choroid is a thin, highly vascular membrane,
                of a dark brown or chocolate color, investing the posterior five-sixths of the
                globe;it is pierced behind by the optic nerve, and in this situation is firmly
                adherent to the sclera
                The ciliary body connects the choroid to the circumference of the iris.
                Iris It is a thin, circular, contractile disk, suspended in the aqueous humor
                between the cornea and lens, and perforated a little to the nasal side of its center
                by a circular aperture, the pupil.

     c. Nervous Tunic
                The Retina (tunica interna).—The retina is a delicate nervous membrane, upon
                which the images of external objects are received. Its outer surface is in contact
                with the choroid; its inner with the hyaloid membrane of the vitreous body.
                The rods are cylindrical, of nearly uniform thickness, and are arranged
                perpendicularly to the surface. Each rod consists of two segments, an outer and
                inner, of about equal lengths.
                The cones are conical or flask-shaped, their broad ends resting upon the
                membrana limitans externa, the narrow-pointed extremity being turned to the
                choroid. Like the rods,

The working of human ear is in such a way that the sound waves travel from the outer ear to the
middle ear, which are then transmitted to the inner ear in the form of compressional waves. In the
inner ear, the compressional waves are converted into electric impulses that are perceived by the

3 mean parts:

    o   the outer ear
    o   the middle ear
    o   the inner ear

The outer ear / External -
is shaped like a funnel. Inside
the outer ear is the ear canal,
a tunnel which ends at a
round membrane called the
eardrum. The eardrum
separates the outer ear from
the middle ear. is a visible portion of the ear, which serves as a protective organ for the eardrum.
It collects and guides the sound waves into the middle ear.
Auricle – is the fleshy part of the external ear outside the head.

       Ear Flap (Pinna) - The sound waves enter the ear via the ear flap.
       Ear Canal (Meatus) - The ear canal is about 2 cm in length. It amplifies the sound
        waves and channelizes them to the middle ear. Sweat glands are present in this canal,
        which secretes earwax.

The middle ear is a small air-filled space containing the Eustachian tube and a bridge of three
bones. The Eustachian tube connects your ear and your throat and helps to keep a supply of fresh
air in the middle ear.

       Eardrum - The eardrum, also known as tympanic membrane is a thin membrane that
        acts as a partition between the outer ear and the middle ear. It vibrates as soon as it
        receives the sound waves and transforms the sound energy into the mechanical energy.
       Hammer (Malleus) - It is a tiny bone, located next to the eardrum. Since it lies adjacent
        to the eardrum, the vibrations from the eardrum cause the hammer to vibrate.
       Anvil (Incus) - Anvil is another tiny bone next to hammer; it vibrates in response to the
        vibration of hammer.
       Stirrup (Stapes) - Similar to hammer and anvil, stirrup is a tiny bone in the middle ear;
        eventually, it also vibrates and passes the compressional waves to the inner ear.

The inner ear is the organ in our body responsible for hearing and balance. In the inner ear we
find the cochlea (coke'- lee-a). The cochlea, which is spiral-shaped like a snail's shell, is made of
three coils of bone. The coils are filled with special fluids (liquids). You already know that the
stapes fits into the oval window on one side of the cochlea. Below the cochlea is the round

       Cochlea - The cochlea or the spiral tube is a rolled structure that can stretch to about 3
        cm; the membrane lining of cochlea consists of numerous nerve cells.
       The hair-like nerve cells respond differently to various frequencies of vibrations, which
        ultimately lead to generation of electrical impulses.
       Semicircular Canals - These are fluid-filled loops, attached to the cochlea and helps in
        maintaining the balance.
       Auditory Nerve - The electrical impulses, generated by the nerve cells, are then passed
        to the brain.

Taylor holds the world record for the world's                                              longest
tongue, which measures 9.4 centimeters from the                                       tip to the
center of his top lip. He is able to insert his tongue                                into      his

       We have almost 10,000 taste buds inside                                                  our
        mouths; even on the roofs of our mouths.
       In general, girls have more taste buds than                                           boys.
       Taste is the weakest of the five senses.

How our tongue works?
Your tongue and the roof of your mouth are covered with thousands of tiny taste buds. When you
eat something, the saliva in your mouth helps break down your food. This causes the receptor
cells located in your tastes buds to send messages through sensory nerves to your brain. Your
brain then tells you what flavors you are tasting.

Taste Receptor Cells, Taste Buds and Taste Nerves

The sense of taste is mediated by taste receptor cells which are bundled in clusters called taste
buds. Taste receptor cells sample oral concentrations of a large number of small molecules and
report a sensation of taste to centers in the brainstem.

Once taste signals are transmitted to the brain, several efferent neural pathways are activated that
are important to digestive function. For example, tasting food is followed rapidly by increased
salivation and by low level secretory activity in the stomach.

Among humans, there is substantial difference in taste sensitivity. Roughly one in four people is a
"supertaster" that is several times more sensitive to bitter and other tastes than those that taste
poorly. Such differences are heritable and reflect differences in the number of fungiform papillae
and hence taste buds on the tongue.

Have you ever thought about why foods taste different? It's really quite amazing. Your tongue
and the roof of your mouth are covered with thousands of tiny taste buds. When you eat
something, the saliva in your mouth helps break down your food. This causes the receptor cells
located in your tastes buds to send messages through sensory nerves to your brain. Your brain
then tells you what flavors you are tasting.
                                        Taste buds probably play the most important part in
                                        helping you enjoy the many flavors of food. Your taste
                                        buds can recognize four basic kinds of tastes: sweet, salty,
                                        sour, and bitter. The salty/sweet taste buds are located near
                                        the front of your tongue; the sour taste buds line the sides
                                        of your tongue; and the bitter taste buds are found at the
                                        very back of your tongue.

                                        Taste Sensations

                                        The sense of taste is equivalent to excitation of taste
                                        receptors, and receptors for a large number of specific
                                        chemicals have been identified that contribute to the
                                        reception of taste. Despite this complexity, five types of
                                        tastes are commonly recognized by humans:

       Sweet - usually indicates energy rich nutrients
       Umami - the taste of amino acids (e.g. meat broth or aged cheese)
       Salty - allows modulating diet for electrolyte balance
       Sour - typically the taste of acids
       Bitter - allows sensing of diverse natural toxins

        -   Sweet – originates from organic molecules such as hydrogen carbon and oxygen.
        -   Bitter – composed of nitrogen
        -   Sour composed of acid
        -   Salty – molecules are being dissolved into ion (electronically charged particles) when
            placed in water.

                                                        One of the most visible organs on the front
                                                        of your face is the nose. Anatomically, a
nose is a vertebrate respiratory organ that covers two nostrils in humans. Nostrils are those two
holes visible in the front of the nose, responsible for reception and expulsion of air for respiration
purposes. A septum proceeds from deep within the nose near the skull where it's made of thin
bony pieces.

Our sense of smell is connected really well to our memory. For instance, the smell of popcorn can
remind you of being at the movies with a friend or the smell of tar can remind you of riding in a
car to the beach.

Humans have seven primary odors that help them determine objects. Listed below are the seven

                            Odor          Example               Pictures
                            Camphoric     Mothballs             Picture
                            Musky         Perfume/Aftershave Picture
                            Roses         Floral                Picture
                            Pepperminty Mint Gum                Picture
                            Etheral       Dry Cleaning Fluid Picture
                            Pungent       Vinegar               Picture
                            Putrid        Rotten Eggs           Picture

While your other four senses (sight, hearing, smell, and taste) are located in specific parts of the
body, your sense of touch is found all over. This is because your sense of touch originates in the
bottom layer of your skin called the dermis. The dermis is filled with many tiny nerve endings
which give you information about the things with which your body comes in contact. They do
this by carrying the information to the spinal cord, which sends messages to the brain where the
feeling is registered.
                                                       The nerve endings in your skin can tell you
                                                       if something is hot or cold. They can also
                                                       feel if something is hurting you. Your body
                                                       has about twenty differnt types of nerve
                                                       endings that all send messages to your
                                                       brain. However, the most common
                                                       receptors are heat, cold, pain, and pressure
                                                       or touch receptors. Pain receptors are
                                                       probably the most important for your safety
                                                       because they can protect you by warning
                                                       your brain that your body is hurt!

                                                        Some areas of the body are more sensitive
                                                        than others because they have more nerve
                                                        endings. Have you ever bitten your tongue
                                                        and wondered why it hurt so much? It is
                                                        because the sides of your tongue have a lot
of nerve endings that are very sensitive to pain. However, your tongue is not as good at sensing
hot or cold. That is why it is easy to burn your mouth when you eat something really hot. Your
fingertips are also very sensitive. For example, people who are blind use their fingertips to read
Braille by feeling the patterns of raised dots on their paper. To learn more about Braille, click on
the word "Braille" located on the left-hand side of this page!

  You have more pain nerve endings than any other type.
  The least sensitive part of your body is the middle of your back.
  The most sensitive areas of your body are your hands, lips, face, neck, tongue, fingertips and
  Shivering is a way your body has of trying to get warmer.
  There are about 100 touch receptors in each of your fingertips.
  Rattlesnakes use their skin to feel the body heat of other animals.

The       skin      is      the      main      organ      of       the     sense       of      touch.
It     is    one       of     the     bodies     largest     and     most      complex       organs.
It           weighs               from            six           to            ten            pounds.
It is made of two layers, the epidermis or the top layer, and the dermis or the bottom layer.
The top part of the epidermis is a layer of dead skin cells. These flake off and are replaced all the
We          lose          about        50          milion        skin         cells        everyday.
The skin contains hair follicles, nerve endings, sweat glands, and blood vessels.
The skin is not equally thick al over your body. The soles of your feet are the thickest. And the
eyelid has the thinnest skin on the entire body.
The skin contains numerous sensory receptors which receive information from the outside
The sensory receptors of the skin are concerned with at least five different senses: pain, heat,
cold,                       touch,                        and                         pressure.

The five are usually grouped together as the single sense of touch in the classification of the five
senses              of              the             whole               human                  body.
The       sensory      receptors       vary     greatly       in     terms        of      structure.
For example, while pain receptors are simply unmyelinated terminal branches of neurons, touch
receptors form neuronal fiber nets around the base of hairs and deep pressure receptors consist of
nerve       endings       encapsulated        by       specialized       connective          tissues.

Receptors     also     vary    in   terms     of    abundance      relative     to   each    other.
For example, there are far more pain receptors than cold receptors in the body.
Finally, receptors vary in terms of the concentration of their distribution over the surface of the
body, the fingertips having far more touch receptors than the skin of the back.

                                                                   Nerve fibers that are attached
                                                                   to different types of skin
                                                                   receptors either continue to
                                                                   discharge during a stimulus
                                                                   "slowly-adapting" or respond
                                                                   only when the stimulus starts
                                                                   and sometimes when a
                                                                   stimulus     ends      "rapidly-
                                                                   adapting". In other words,
                                                                   slowly-adapting nerve fibers
                                                                   send     information      about
                                                                   ongoing stimulation; rapidly-
                                                                   adapting nerve fibers send
                                                                   information      related      to
                                                                   changing      stimuli.      The
Pacinian corpuscle receptor is a classic example of a rapidly-adapting type receptor. The Ruffini
                                                          nerve ending is a slowly-adapting type

                                                            Anatomy of the Skin

                                                            The skin is the body's largest organ,
                                                            covering the entire body. In addition to
                                                            serving as a protective shield against
                                                            heat, light, injury, and infection, the
                                                            skin also:

       regulates body temperature.
       stores water and fat.
       is a sensory organ.
       prevents water loss.
       prevents entry of bacteria.
The skin's characteristics (thickness, color, texture) vary. For instance, the head contains more
hair follicles than anywhere else, while the soles of the feet contain none. In addition, the soles of
the feet and the palms of the hands are much thicker. The skin is made up of the following layers,
with each layer performing specific functions:

        epidermis
        dermis
        subcutaneous fat layer

epidermis The epidermis is the thin outer layer of the skin and consists of three parts:

                    stratum                        corneum                      (horny                        layer)
                     This layer consists of fully mature keratinocytes which contain fibrous proteins (keratins). The
                     outermost layer is continuously shed. The stratum corneum prevents the entry of most foreign
                     substances as well as the loss of fluid from the body.
                    keratinocytes                                   (squamous                                  cells)
                     This layer, just beneath the stratum corneum, contains living keratinocytes (squamous cells),
                     which mature and form the stratum corneum.
                    basal                                                                                      layer
                     The basal layer is the deepest layer of the epidermis, containing basal cells. Basal cells
                     continually divide, forming new keratinocytes that replace the cells that are shed from the
                     skin's surface.

             The epidermis also contains melanocytes, which are cells that produce melanin (skin pigment).
dermis       The dermis is the middle layer of the skin. The dermis contains the following:

                    blood vessels
                    lymph vessels
                    hair follicles
                    sweat glands
                    collagen bundles
                    fibroblasts
                    nerves

             The dermis is held together by a protein called collagen, made by fibroblasts. This layer also contains
             pain and touch receptors.
subcutis     The subcutis is the deepest layer of skin. The subcutis, consisting of a network of collagen and fat
             cells, helps conserve the body's heat and protects the body from injury by acting as a shock absorber.


It has been discovered that even the skin is anesthetized there is a consciousness of pressure.


Thermoception is the sense of heat and the absence of heat (cold) by the skin and including
internal skin passages, or rather, the heat flux (the rate of heat flow) in these areas. The cold
receptors play an important part in the dogs sense of smell, telling wind direction, the heat
receptors are sensitive to infrared radiation and can occur in specialized organs for instance in pit
vipers. The thermoceptors in the skin are quite different from the homeostatic thermoceptors in
the brain (hypothalamus) which provide feedback on internal body temperature.


Nociception (physiological pain) signals near-damage or damage to tissue. The three types of
pain receptors are cutaneous (skin), somatic (joints and bones) and visceral (body organs). It was
previously believed that pain was simply the overloading of pressure receptors, but research in
the first half of the 20th century indicated that pain is a distinct phenomenon that intertwines with
all of the other senses, including touch. Pain was once considered an entirely subjective
experience, but recent studies show that pain is registered in the anterior cingulate gyrus of the

Motion perception is the process of inferring the speed and direction of elements in a

scene based on visual, vestibular and proprioceptive inputs.

Robert Sternberg – defines stroboscopic motion as ―the perception of motion‖
Induced motion – the visual illusion occurs when the background is moving rather than the figure.
Perceptual constancy – involves complex phenomena in which perception certain that the
moving objects size, shape brightness remain the same.
Stroboscopic effect - the perception of motion produced by stroboscope

Depth perception is the visual ability to perceive the world in three dimensions. Although any
animal capable of moving around its environment must be able to sense the distance of objects in
that environment, the term perception is reserved for humans, who are, as far as is known, the
only beings that can tell each other about their experiences of distances
Depth sensation is the ability to move accurately, or to respond consistently, based on the
distances of objects in an environment. With this definition, every moving animal has some
sensation of depth.

Depth perception arises from a variety of depth cues

Monocular cues provide depth information when viewing a scene with one eye.
              - Relative size - If two objects are known to be the same size (e.g., two trees)
                  but their absolute size is unknown, relative size cues can provide information
                  about the relative depth of the two objects. If one subtends a larger visual
                  angle on the retina than the other, the object which subtends the larger visual
                  angle appears closer.
              - Perspective - The property of parallel lines converging at infinity allows us
                  to reconstruct the relative distance of two parts of an object, or of landscape
              - Aerial perspective - Due to light scattering by the atmosphere, objects that
                  are a great distance away have lower luminance contrast and lower color
                  saturation. In computer graphics, this is called "distance fog".

Binocular cues provide depth information when viewing a scene with both eyes.
         Convergence - This is a binocular oculomotor cue for distance/depth perception. By
virtue of stereopsis the two eye balls focus on the same object. In doing so they converge.
Visual perception is the ability to interpret information and surroundings from visible light
reaching the eye. The resulting perception is also known as eyesight, sight or vision.
Form perception is one of the most basic visual discriminations that a child has to make.
Whether it be the differentiation of the shape of a circle from a square, or the letter B from P, the
ability to perceive the shapes of objects and pictures is an important skill for the developing
child to acquire.
Proximity - posits that when we perceive a collection of objects, we will see objects close to
each other as forming a group.
Similarity - captures the idea that elements will be grouped perceptually if they are similar to
each other
Closure – elements that have continues shape and boundaries are grouped together
Good continuation – perception of smoothly flowing and continues lines are grouped together
instead of disrupted and discontinues ones.
Common movement – elements that share common movements are grouped together.

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