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					  Chapter3

Biological Aspects
        Of
    Psychology
      Biological psychology
• studies the cells, genes, and organs of
  the body and the physical, hormonal, and
  chemical changes involved in behavior
  and mental processes.
  I.       CELLS OF THE NERVOUS
                SYSTEM
• What are neurons and what do they do?
  – A.      Neurons
            » 1 .There are two main cell types in the nervous
                 system.

       •       a) Neurons are specialized to respond
                    rapidly to signals and send signals of
                    their own.

               b)    Glial cells hold neurons together, guide
                     their growth, secrete and absorb chemicals
                     to maintain a stable chemical environment,
                     and send a limited number of signals
                     between neurons.
• 2.   All body cells have some features in
       common.
       » a)   An outer membrane selectively allows only
         some substances to pass in and out.


       » b)   The cell body contains the nucleus.


       » c)   Mitochondria turn oxygen and glucose into
              energy.
• 3.    Neurons have special features that permit
       effective signal communication:
       » a)      An axon is a cell fiber that carries signals
               away from the cell body. Most neurons have
                just one axon.

       » b) A dendrite is a cell fiber that receives signals
              from other neurons and carries information
              toward the neuron’s cell body. Most neurons
              have many dendrites.


 http://icarus.med.utoronto.ca/neurons/index.swf
      dendrite
                                               Axon terminal
                             Node
                             Of
                             ranvier
                 soma




                                       Schwann cell



nucleus                 Myelin
                        sheath
  I.   CELLS OF THE NERVOUS
            SYSTEM
• B. Action Potentials
       – 1.Action potentials are electrochemical
         pulses that      shoot down the neuron’s axon.
         They are ―all-or-none:‖ A neuron either fires
         an action potential at full strength, or does
         not fire at all.

       – 2.After an action potential, there is a brief
         refractory period, during which a neuron
         cannot fire another action potential.
• 3.  The speed of an action potential on a given
      axon is constant, but different neurons
  show different speeds relative to each other.


http://icarus.med.utoronto.ca/neurons/index.swf
      » a)    Action potentials travel faster on axons
        with large diameter or axons wrapped with myelin,
        a white, fatty substance. Such axons are often
        found in the pathways that carry the most
        ―urgent‖ information

      »      1) Multiple sclerosis is a disease in
               which the myelin is destroyed by a
               person’s own immune system.
              Symptoms result because the correct timing
              of neuron signaling is thrown off.


http://icarus.med.utoronto.ca/neurons/index.swf
• C. Synapses and Communication
  Between Neurons
    • 1.    Two neurons communicate at a synapse, a
            connection with only a narrow gap
           separating the two neurons’ membranes.

     2.    Messages cross the synapse in the
           form of chemicals called
           neurotransmitters, released from
            sac-like vesicles within the axon tip.
– 3. An action potential causes vesicles to
     move in the axon tip and release their
    stored neurotransmitters into the space
    between the two neurons.

– 4. Released neurotransmitters ―float‖
     across the synapse to briefly ―bind‖ with
    receptors in the postsynaptic cell
    membrane, usually on a dendrite.
» 5. The interaction between
  neurotransmitters and receptors is very
  specific, like a lock and key: only a
  specific receptor (a ―lock‖) can be
  stimulated by a specific neurotransmitter
  (a ―key‖).
» 6. A signal called a postsynaptic
  potential (PSP) might make action
  potentials in the second, or postsynaptic
  neuron either more or less likely. The
  PSPs sum together at the junction of the
  cell body and the axon. It takes many
  ―fire‖ signals adding together at this
  location to create an action potential.
• II.THE CHEMISTRY OF BEHAVIOR:
  NEUROTRANSMITTERS
• How do biochemicals affect my mood?
Different sets of neurons use different
neurotransmitters.

About 100 neurotransmitters have been identified.

A group of neurons that communicate using the same
neurotransmitter is called a neurotransmitter system.
          A. Three Classes of
           Neurotransmitters
• 1. Small molecules
     a) Acetylcholine is used by sets of neurons involved in
        controlling movement of the body, in making memories, and
        in slowing the heartbeat and activating the digestive system.
     b) Norepinephrine affects sleep and wakefulness, learning,
        mood, and vigilance. It has also been implicated in depression.
   c) Serotonin affects sleep and wakefulness, mood, aggression,
      and impulsive behaviors. Also, eating carbohydrates can increase
      serotonin, and increased serotonin reduces the desire for
      carbohydrates.
      (1) Malfunctions in serotonin systems can result in mood and appetite
            problems seen in some types of obesity, premenstrual tension
          , and depression.
     (2) Antidepressant medications such as Prozac, Zoloft, and Paxil
            are thought to act on serotonin systems to relieve some of the
            symptoms of depression.
• d) Dopamine is used by sets of neurons involved in
  controlling movement, and damage to these systems
  contributes to shakiness experienced by people with
  Parkinson’s disease. Other dopamine systems are
  involved in the experiencing of reward, or pleasure,
  which is vital in shaping and motivating behavior.
• (1) Dopamine systems play a role in the rewarding
  properties of many drugs, including cocaine.
• (2) Certain dopamine systems are suspected to be
  responsible for the perceptual, emotional, and
  thought disturbances associated with schizophrenia.
• e) GABA (gamma-amino butyric acid) is
  the main inhibitory neurotransmitter in
  the brain—it slows down the brain’s
  neural activity.
       – (1)      Some drugs amplify the inhibitory action of
         GABA. One example is alcohol, which results in
         impairments of thinking, judgment, and motor skills.
         Drugs that interfere with GABA’s inhibitory effects
         produce intense repetitive electrical discharges,
         known as seizures.
       – (2)Impaired GABA systems are thought to contribute
         to severe anxiety, Huntington’s disease, and epilepsy.
• f) Glutamate is the main excitatory
  neurotransmitter in the brain.
   Overactivity of glutamate synapses can
  cause neurons to die by ―exciting them to
   death.‖
  – (1)     Blocking glutamate receptors immediately
    after brain trauma can prevent permanent brain
    damage.
  – (2)     Glutamate may contribute to the loss of
    brain cells in Alzheimer’s disease.
        A. Three Classes of
         Neurotransmitters
• 2. Peptides: Hundreds of chemicals
  called peptides have been found to act
  as neurotransmitters.

 Examples of these are endorphins,
 which are used in brain systems involved
 in pain perception. Opiate drugs (e.g.,
 morphine) relieve pain by binding to
 endorphin receptors.
        A. Three Classes of
         Neurotransmitters
• 3. Gases: Two toxic gases that
  contribute to air pollution have been
  recently discovered to act as
  neurotransmitters:
• nitric oxide and carbon monoxide.
• III.   The Divisions of the
•            NERVOUS
              SYSTEM:



   How is my nervous system organized?
• A. Central Nervous System
•        1. Brain
•              a. major organ of the
                  nervous system and body’s
                  functioning
•        2. Spinal Cord
•              a. thick column of nerves
                   encased in bony spine
•
• B. Peripheral Nervous System
•        1. Components of the nervous
            system other than the brain
            and spinal cord.
IV Peripheral Nervous System
•   A. Somatic Nervous System
      1. Comprised of sensory and motor
         neurons

      2. Links communication between central
         nervous system and sense organs,
        muscles.
B. Autonomic Nervous System (internal
   body processes)
–     1. Sympathetic nervous system
         a. prepares body to meet physical
            demands or stress.
         b. Increases heart rate, breathing,
             levels of blood sugar
2. Parasympathetic Nervous system
   a. Fosters bodily processes
    –   breathing
    –   digestion
    –   heart rate
    –   urination/.defecation
    –   levels of oxygen and carbon dioxide in bloodstream
   b. directs the body’s functions to conserve
      energy (e.g., slower heart rate, increased
      digestive activity). Parasympathetic
      activity helps ―calm‖ a person after
      increased sympathetic arousal.
Differences between the Sympathetic and Parasympathetic systems
The autonomic nervous system, part of the PNS is made up of two divisions:
the sympathetic and parasympathetic systems.

Characteristic               Sympathetic                  Parasympathetic

When functioning?       emergencies                      normal/everyday

Digestive system         inhibits/slows down               promotes

Pupil                     dilates                         constricts

Heartbeat                  accelerates                    retards

Breathing rate            increases                        retards
•   V.    THE CENTRAL NERVOUS
•           SYSTEM:



         How is my brain "wired?"
                                           Fun Facts About The Brain




 How much does human brain weigh?
 At birth our brains weigh and average about 4/5 lbs), as adults the brain averages about 3 lbs).


 If Stretched out the cerebral cortex would be 0.23 sq. m(2.5sq.ft), the area of a night table

 The composition of the brain = 77-78% water, 10-12% lipids, 8% protein, 1% carbs, 2% soluble organics, 1% inorganic salt.


The cerebellum contains half of all the neurons in the brain but comprises only 10% of the brain.
                       The cerebral cortex is about 85% of the brain.


 750-1000ml of blood flow through the brain every minute or about 3 full soda cans.
     The brain can stay alive for 4 to 6 minutes without oxygen.
                     After that cells begin die.

     The slowest speed at which information travels between neurons is 416 km/h
                                 or 260 mph,
          thats as "slow" as todays supercar's top speed (Bugatti)



   The energy used by the brain is enough to light a 25 watt bulb.

More electrical impulses are generated in one day by a single human brain than
                 by all the telephones in the world.

          How much does human brain think? 70,000 is the number of thoughts
                          that it is estimated the
                 human brain produces on an average day.


After age 30, the brain shrinks a quarter of a percent (0.25%) in mass each year.
       A. The Spinal Cord

• 1. Reflexes are simple, involuntary
  behaviors controlled by spinal cord
  neurons, without requiring instructions
  from the brain.
• 2. Reflexes are controlled by feedback
  systems, regulatory ―circuits‖ where an
  action’s consequences alter the original
  source of the action.
                       B. The Brain

•   A number of tools have been developed for monitoring the brain’s
    structure and activity:
•   1.    The earliest technique is called an electroencephalogram (EEG),
    which measures general electrical activity through electrodes on the
    scalp

•   2.    A newer technique is a positron emission tomography (PET) scan,
    which records the location of radioactive substances that were
    injected into the bloodstream. These show the location of brain
    activity during specific tasks.

•   3.    Another recent technique is magnetic resonance imaging (MRI),
    which records radio frequency waves after exposure to a magnetic
    field. These provide clear details on the structure of the brain.

•   4.   The newest technique, called functional MRI or fMRI, detects
    changes in blood flow to provide a ―moving picture‖ of the brain.
            C. The Hindbrain

• The hindbrain is found just above the spinal cord and
  is composed of the following structures:
• 1. The medulla performs vital coordination of the
  basic life functions (e.g., blood pressure, heart rate,
  breathing).
• 2. The reticular formation is a web of neurons that
  helps alert and arouse other brain areas.
• 3. The cerebellum maintains balance, coordinates
  fine motor movements, stores a memory code for
  well-rehearsed behaviors, and participates in
  cognitive tasks such as reading.
         D. The Midbrain

• The tiny midbrain relays information
  from the eyes, ears, and skin and
  controls certain types of automatic
  behaviors. The midbrain and its
  connections to the forebrain permit the
  smooth initiation of movement.
                E. The Forebrain

• The forebrain, the largest part of the brain, regulates many
  complex aspects of behavior and mental phenomena.

• 1.   The thalamus processes inputs from sense organs and then
  relays sensory information to appropriate ―higher‖ forebrain
  areas. It is the primary sensory relay into the rest of the brain.

• 2. The small hypothalamus has some of the brain’s most
  important control systems. It regulates many physiological
  feedback systems, coordinating hunger, thirst, temperature
  regulation, and sexual behavior. It directly influences both the
  autonomic and endocrine systems. It contains the
  suprachiasmatic nucleus, an endogenous ―clock‖ that sets
  biological rhythms for the body.
• 3. The amygdala is especially important
  for creating associations between two
  sensory modalities or between sensory
  and emotional information.
• 4. The hippocampus is critical to the
  ability to form new memories.
      F. The Cerebral Cortex

• 1. The forebrain’s outer surface, the
  cerebral cortex, is a thin sheet of neurons.
  In humans, the sheet folds in on itself, giving
  the brain its characteristic wrinkled
  appearance.
• 2. The cerebral cortex is dividing down the
  middle, creating two halves called the left and
  right cerebral hemispheres. The corpus
  callosum connects the two halves.
• 3. The folds of cortex produce gyri (ridges), and
  sulci or fissures (valleys or wrinkles), on the brain’s
  outer surface.
            a. Several deep sulci make
                      convenient markers for dividing
                     the cortex of each hemisphere
                      into four lobes:
                   frontal
                   parietal
                  occipital
                   temporal
 G. Sensory and Motor Cortex
• Sensory cortex and motor cortex are two of the functional
  areas of the cortex.
• 1.   Each region of the sensory cortex receives and processes
  input from a single sensory organ.
              a)       Inputs from the eyes are sent to the visual
                       cortex in the occipital lobe.
              b)       Inputs from the ears are sent to the
                       auditory cortex in the temporal lobe.
              c)       Inputs from the skin sensory organs connect
                       to the somatosensory cortex in the parietal
                       lobe.
Cortical AreaFunction
Prefrontal Cortex              Problem Solving, Emotion, Complex
                               THought
Motor Association Cortex       Coordination of complex movement
Primary Motor Cortex           Initiation of voluntary movement
Primary Somatosensory Cortex   Receives tactile information from the body
Sensory Association Area       Processing of multisensory information
Visual Association Area        Complex processing of visual information
Visual Cortex                  Detection of simple visual stimuli
Wernicke's Area                Language comprehension
Auditory Association Area      Complex processing of auditory information
Auditory Cortex                Detection of sound quality (loudness, tone)
Broca's Area                   Speech production and articulation
     H. Association Cortex
• 1. Most of the cortex in each lobe is
  association cortex, with no direct
  sensory inputs or direct motor outputs.
       a) Since each region of association cortex is
          involved in many functions, damage to
         association cortex creates a variety of different
         psychological symptoms.
• b) Some regions of the association cortex are
  specifically involved in language processing.
             (1)    Brain damage in these areas may
                    cause aphasia, problems
                    understanding or producing speech.

                   (a) Broca’s area is a region of association cortex
                   , usually in the left frontal lobe. Damage to this
                    region causes difficulty speaking smoothly and
                    grammatically, a condition called Broca’s aphasia.

                  (a) Wernicke’s area is a region of the association
                    cortex, usually in the left temporal lobe.
                   Damage to this region leaves fluency intact, but makes
                   it difficult to understand the meaning of words
                   or to speak understandably.
            I The Divided Brain:
               Lateralization
• 1.   The brain is composed of two sides referred to as
       hemisperes.
          a. The hemispheres are connected via the corpus callosum


  2. Information received on one side of the body is transmitted
     to the opposite hemisphere of the brain.
       J. Plasticity in the Brain
• 1.    Brains add or change synapses due to one’s experiences.
                     *this may be the key to making new memories
                     Or learning new things.


  2. Brain damage is hard to repair because the adult nervous system
    does not automatically replace damages cells and restore lost functions
   VI The Endocrine System
• A.   -Consists of glands that secrete substances called
       hormones into the bloodstream.

  B. Hormones are produced by several different glands:
    Pituitary, thyroid, adrenal, testes and ovaries
• 1. Pituitary Gland

       a. known as the “master gland:”
         1. Stimulated by the hypothalamus.
                   E.g. growth hormones (regulates growth of
                 muscles, bones and glands),lactation, labor.
• 2. Thyroid Gland

      1. Produces hormone that effects the body’s metabolism-thyrox
         a. Hypothyroidism- overweight
         b. Hyperthyroidism-underweight,sleeplessness
         v. Cretinism-children with too little thyroxin-
                 stunted growth,retardation.
• 3. Adrenal Gland


        a. Outer layer secretes cortical steroids.
           1. increase resistance to stress (adrenaline
                   and nonadrenaline)
           2. Promote muscle development.
           3. Cause liver to secrete stored sugars.
• 4. Testes and Ovaries
      1. Testes
         a. produces testosterone -Aides growth of bone
             and muscle
         b. Aides in primary and secondary sex characteristics.

      2. Ovaries
         a. Produce estrogen and progesterone
      - b. Aides in primary and secondary sex characteristics.
         c. Progesterone stimulates formation of reproductive
            organs, also helps prepare body for pregnancy.
         d. Together they regulate menstrual cycle.
         e. changes=PMS

				
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