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Chapter 3

Psychology 1000 Chapter Notes - Chapter 3: Positron Emission Tomography, Ct Scan, Peripheral Nervous System

Course Code
PSYCH 1000
Biggs- Universityof Western Ontario

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Chapter 3: Biological Psychology
a) The Neural Bases of Behaviour
The basic building blocks of the nervous system are linked together in circuits and
composed of:
1. A cell body (soma) - contains necessary chemical structures to keep the neuron alive.
The nucleus carries the genetic information.
2. Dendrites- branchlike fibers emerging from the cell body, which, like antennas, collect
messages from neighbouring neurons and send them to the cell body. Incoming
information is combined and processed.
3. Axon- conducts electrical impulses away from the cell body to other neurons, muscles
or glands. They branch out to dendrites and transfer information.
Glial cells surround neurons and hold them in place, manufacture nutrients, form the
myelin sheath around axons and absorb toxins.
Blood- brain barrier- prevents substances (i.e. toxins) from entering the brain
Nerve Conduction:
Neurons generate electricity and release chemicals
Neurons are electronegative- polarized
Action Potential:
Depolarization- a sudden reversal in the neuron’s membrane voltage, during which the
membrane voltage momentarily moves from -70 millivolts to +40
Potentials- when dendrites are stimulated by axons, a shift occurs
Need enough stimulation to reach the action potential threshold
Neuron discharges with an action potential
All-or-none law- either occurs with maximum intensity or doesn’t occur at all.
Graded potentials add ion channels (protein structures) to change the membrane
Ion channels allow ions to cross the membrane or enter/leave the cell
If the threshold is reached, a neuron will fire
Refractory period- when the membrane is not excitable and cannot discharge an action
The Myelin Sheath:
A fatty, whitish insulation layer derived from glial cells during development
Interrupted by the nodes of Ranvier

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Create high conduction speeds
Cause for timing of nerve impulses
Synaptic Transmission:
Synapse- a functional (but not physical) connection between a neuron and it’s target
Synaptic cleft- a tiny group or space between the axon terminal of one neuron and the
dendrite of the next neuron
1. Neurotransmitters
Chemical substances that carry messages across the synapse to either other neurons or
inhibit their firing
a) Synthesis- chemical molecules formed in neuron
b) Storage- molecules stored in synaptic vessels within axon terminals
c) Release- when AP comes down the axon, molecules release into fluid space
d) Binding- cross synaptic space and bind to receptor sites
e) Deactivation
2. Excitation, Inhibition and Deactivation
Binding produces a chemical reaction, which can:
a) Depolarize (excite) the postsynaptic membrane by stimulating the flow of sodium ions
- called excitatory transmitters, which can exceed APT
b) Chemical reaction can hyperpolarize the membrane by stimulating ion channels,
allowing sodium ions to flow out and Cl to flow in
- becomes more negative, harder to reach APT
- called inhibitory transmitters
Deactivation occurs by:
- By other chemicals
- By reuptake- transmitter molecules are reabsorbed into the axon terminal
Specialized Transmitter Systems:
Simple amino acids, glutamate (glutamic acid) and gamma-amino-butyric acid (GABA)
a) Glutamate- excitatory, learning and memory
b) GABA- inhibitory, motor control and anxiety control
c) Acetylcholine (Ach)- memory and muscle activity, excitatory
d) dopamine- can treat schizophrenia
e) serotonin- mood, eating, sleep and sexual behaviour
f) endorphins- increased well-being, lessened pain

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b) The Nervous System
1. Sensory Neurons- carry input messages from sense organs to the spinal cord and brain
2. Motor Neurons- transmit output impulses from the brain and spine to muscles and organs
3. Interneurons- connective/associative functions, linking input and output
Central nervous system- neurons in the brain and spinal cord
Peripheral nervous system- neurons that connect central with muscles, glands and
sensory receptors
The Peripheral Nervous System:
All neutral structures outside of the brain and spinal cord
a) The Somatic Nervous System
- sensory neurons- transmit messages from eyes, ears, etc. and the motor neurons that
send messages from the brain and spinal cord to the muscles that control our voluntary
- groups of sensory organs= sensory nerves
- groups of motor neuron axons= motor nerves
b) The Autonomic Nervous System
- controls the glands and the smooth (involuntary) muscles that form the heart, blood
vessels and lining of the stomach/intestines
- respiration, circulation, digestion, motivation, emotional behaviour and stress responses
i) sympathetic- activation/arousal function, “fight or flight”, a unit, heart rate rises
ii) parasympathetic- slows down body processes, heart rate lowers
The Central Nervous System
- Spinal cord and the brain
a) The Spinal Cord
Nerves enter/leave central nervous system via spine
Neurons protected by vertebrae (bones of the spine)
Spinal reflexes- simple stimulus/response sequences, triggered without brain, speeding up
reaction time
b) The Brain
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