CHAPTER 3: BIOLOGICAL BASES OF BEHAVIOR

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CHAPTER 3 BIOLOGICAL BASES OF BEHAVIOR
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COMMUNICATION IN THE NERVOUS SYSTEM
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NERVOUS TISSUE THE BASIC HARDWARE

• 2 major categories of cell in the nervous system
• 1 Glia---glue provide structural support and
  insulation for neurons
• 2 Neuron---individual cell in the nervous system
  that receive, integrate, and transmit information

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NEURON STRUCTURE

• Soma cell body contains nucleus
• Dendrite receive info.
• Axon long, thin fiber transmits signals from
  soma to other neurons or muscles/glands
• Myelin sheath insulating material (glia) around
  axon
• Terminal button secrete neurotransmitters
• Synapse space btwn neurons info transmitted

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NEURAL IMPULSE AT REST

• Complex electrochemical reaction
• charged Na and K ions and neg. charged chloride
  ions flow across membrane
• Higher concentration of neg ions inside cell
  creates voltage
• Resting potential a neurons stable, negative
  charge when the cell is inactive (c. -70
  millivolts)

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NEURAL IMPULSE ACTION POTENTIAL

• When neuron is stimulated
• Ion channels open charged Na ions rush in
• Charge is less neg. or even pos.
• This creates an Action potential brief shift in
  a neurons electrical charge that travels along
  an axon

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NEURAL IMPULSE REFRACTORY

• Na channels close
• Absolute refractory period min. length of time
  after an action potential during which another AP
  cannot begin (1 or 2 milliseconds)

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ALL-OR-NONE LAW

• Neuron either fires or doesnt
• Action potentials are all the same size
• Rate of action potentials tells strength of
  stimuli
• Size of axon effects rate

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SYNAPSES

• Neurons do not touch
• Synaptic cleft microscopic gap btwn terminal
  button of one neuron and the cell membrane of
  another
• Msgs. in the form of neurotransmitters chemical
  info. from one neuron to another

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NEUROTRANSMITTERS

• Most stored in synaptic vesicles in the terminal
  buttons
• They diffuse into the synaptic cleft
• Picked up by receptor sites of receiving neuron

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POSTSYNAPTIC POTENTIALS (PSP)

• Def a voltage change at a receptor site on a
  postsynaptic cell membrane
• Vary in size
• Increase or decrease probability of an impulse

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TYPES OF MESSAGES

• Excitatory PSP a positive voltage shift
  increases likelihood that a postsynaptic neuron
  will fire action potentials
• Inhibitory PSP neg. voltage shift decreases
  likelihood that a postsynaptic neuron will fire
  action potentials

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REUPTAKE

• Def a process in which neurotransmitters are
  sponged up from the synaptic cleft by the
  presynaptic neuron
• Recycles material
• Some NTs are inactivated by enzymes or removed
  (drift away)

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NEUROTRANSMITTERS AND BEHAVIOR

• Over 100 possible NTs have been identified
• Specific NTs only work in specific receptors
• This is called the lock-and-key principle
• Meant to prevent mixing of NTs

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ACETYLCHOLINE (ACh)

• Only transmitter btwn motor neurons and voluntary
  muscles
• Also contributes to attention, arousal, and
  possibly memory

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AGONIST AND ANTAGONIST

• Agonist chemical that mimics the action of a
  neurotransmitter
• Antagonist chemical that opposes the action of a
  neurotransmitter---they block receptors

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MONOAMINES

• Include dopamine, norepinephrine, and serotonin
• Dopamine voluntary movement, pleasurable
  emotions
• Serotonin sleep and wakefulness aggression and
  impulsivity
• Norepinephrine modulation of mood, arousal

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ABNORMALITIES WITH MONOAMINES

• Low levels of norepinephrine and serotonin
  synapses tied to depression
• Abnormal dopamine activity tied to schizophrenia

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ENDORPHINS

• Def the family of internally produced chemicals
  that resemble opiates in structure and effect
• Discovered by study of morphine effects
• Regulate pain, pleasure