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 functioning. 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. HISTORY AND DEVELOPMENT OF PSYCHOLOGY 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. COMPONENTS OF PSYCHOLOGY 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. FIELDS OF PSYCHLOGY 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 system. Health psychology- it refers to the relationship between the mental and physical health of the body. 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 organization. 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 VS. NATIVISM 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 conditioning. 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. EARLY SCHOOLS OF PSYCHOLOGY 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. MODERN PERSPECTIVES OF PSYCHOLOGY 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 behavior. BIOLOGICAL ASPECTS OF HUMAN BEHAVIOR 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 gamble. 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 glands. 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 infundibulum. 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 pigmentation. 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 pregnancy. 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 levels. 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 produced. 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 scrotum. 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 ignored. 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 breathing. 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 body. 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. 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 functions. 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. Neurons 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 organs. 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 neutrons. 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 AND PERCEPTION 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. THE SENSES Sight 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 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 deafness. Taste 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 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 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. Protection 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. TRIVIA 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, SENSE OF HEARING 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 brain. 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 window. 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. Stephen 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 nostrils! 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 odors. 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 feet. 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 time. 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. SENSORY RECEPTORS The skin contains numerous sensory receptors which receive information from the outside environment. 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 receptor. 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. Pressure It has been discovered that even the skin is anesthetized there is a consciousness of pressure. Temperature 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. Pain 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 brain. 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 features. - 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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