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Chapter 3

PSY100Y5 Chapter Notes - Chapter 3: Midbrain, Agonist, Twin

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Dax Urbszat

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Sep 19, 2015
Chapter 3: The Biological Bases of Behaviour
Sandra Witelson, extensive collection of preserved human brains
Opportunity to study Albert Einstein’s brain
Kept by Tom Harvey, a hospital pathologist, then handed the brain to Witelson
Einstein’s brain seemed slightly different compared to a normal brain, which gave him a
higher IQ
fMRI technology helped analyze patients who are in the vegetative states
Nervous System
Neurons: individual cells that receive, integrate, and transmit information
Links communication with other neurons
Some can receive signals from outside the nervous system in order to move the body
Soma/cell body: cell nucleus and chemical machinery common in most cells
Dendrite: parts of a neuron that receives information
Receptor sets
Axon: long, thin fibre that transmits signals away from the soma to other neurons, muscles
or glands
Information flows into the soma (cell body), then away through the axon
Myelin sheath: insulating material, covers/protects axons
Speeds up the transmission of signals along axons
Deterioration of the myelin sheath affects the signals that are being transmitted
Multiple sclerosis is the result of myelin sheath deteriorating
Terminal buttons: cluster of small knobs at the end of an axon that secretes
Activate neighbouring neurons
Synapse: information is transmitted from one neuron to another
Aka, information is received at the dendrites, passed through soma along the axon, transmitted
to dendrites of other cells at meeting points called synapses.
Glia: cells found throughout the nervous system, providing support for neurons and holds
the brain together
Glia are smaller then neurons, though they outnumber neurons (1:10)

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Sep 19, 2015
Supply nourishment to neurons, removes neurons’ waste products
Provides insulation around axons
Glia sends and receives chemical signals
Memory formation
Deterioration may lead to Alzheimers
Psychological disorders (schizophrenia) and mood disorders
Neural impulse
Electric charge of the neutron that is measured with a pair of electrodes
Burst of electrical atoms hit down to the terminal button, forcing neurotransmitters out
Ions (electrically charged atoms and molecules) both inside and outside the neuron
Resting potential of a neuron: stable, negative charge when cell is inactive
Stimulation of neuron changes the voltage (action potential)
Shift in neuron’s electrical charge
Needs time to regenerate after an action potential
Absolute refractory period: minimum length after an action potential during which
another action potential cannot begin
Usually one or two millisecond
Stronger stimulus -> faster neural impulses
Graded potential
– > + lowers the amount of energy in the neuron
Neuron holds energy like a battery
Resting potential, will not fire
Generated at dendrites, conducted along membrane
Spike: pulse of electrical energy that is sent to the axon
Synapse: neural impulse reaches the axon’s terminal
Two neurons do not touch
All or nothing, fires slow or as fast as it can
Stimulus intensity
Separated by the synaptic cleft: microscopic gap between terminal button of one neuron
and the cell membrane of another neuron
Presynaptic neuron: sends signal across the gap

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Sep 19, 2015
Postsynaptic neuron: receives the signals
Neurotransmitters: chemicals that transmit information from one neuron to another
Chemicals are stored in small sacs (synaptic vesicles), contains neurotransmitters
Released when the membrane of the presynaptic cell spill its contents into the synaptic
Bind with molecules in the postsynaptic cell; receptor sites are specifically tuned to
respond to some neurotransmitters and not others
Inhibitory or excitatory
Postsynaptic potential (PSP): voltage change at receptor site on a postsynaptic cell
Combination of a neurotransmitter and a receptor molecule
Varies in sizes, increase or decrease the probability of neural impulse
Excitatory PSP: positive voltage shift, increasing the likelihood of postsynaptic neuron
Inhibitory PSP: negative voltage shift, decreasing the likelihood of postsynaptic neuron
Nature of PSP depends on receptor sites
Reuptake: process in which neurotransmitters are sponged up from synaptic cleft by
presynaptic membrane
Allows for synapses to recycle their materials
Long term potentiation: long-lasting increase in neural excitability in synapses
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