Summary of Chapter 3

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11 Dec 2010
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Chapter Three – The biological bases of behavior
Communication in the nervous system
Key parts of the neuron
-Cells in the nervous system fall into two categories:
1)Neurons
-Neurons: individual cells in the nervous system that
receive, integrate, and transmit information.
-Soma (=cell body): contains the cell nucleus and much of
the chemical machinery common to most cells.
-Dendrites: parts of a neuron that are specialized to receive
information.
-Axon: a long, think fiber that transmits signals away from the
soma to other neurons or to muscles or glands.
-Myelin sheath: insulating material, derived from glial cells,
that encases some axons.
-Terminal buttons: small knobs that secrete chemicals
called neurotransmitters.
-Synapse: junction where information is transmitted from one
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neuron to another.
2)Glia
-Glia: cells found throughout the nervous system that provide
various types of support for neurons.
-Supply nourishment to neurons, help remove neurons’ waste
products, and provide insulation around many axons.
The Neural impulse
-The resting potential: when a neuron is stable, negative
charge when the cell is inactive.
-Action potential: a very brief shift in a neuron electrical
charge that travels along an axon.
-Absolute refractory period: the minimum length of time
after an action potential during which another action potential
cannot begin.
-Either neuron fires or it doesn’t, and its action potential are
all the same size. Weaker stimuli do not produce smaller AP.
The synapse where neurons meet
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-Two neurons don’t actually touch. They are separated by the
synaptic cleft, a microscopic gap between the terminal
button of one neuron and the cell membrane of another
neuron.
-Presynaptic neuron: neuron that sends a signal across the
gap.
-Postsynaptic neuron: neuron that receives the signal.
-Neurotransmitters chemicals that transmit information
from one neuron to another are released when a vesicle
fuses with the membrane of the presynaptic cell and its
contents spill into the synaptic cleft. There, they bind with
special molecules in the postsynaptic cell membrane at
receptor sites.
-Postsynaptic potential (PSP) - a voltage change at a
receptor site on a postsynaptic cell membrane occurs
when a neurotransmitter and a receptor molecule combine.
They do not follow all-or-none-law. They vary in size.
-Excitatory PSP - a positive voltage shift that increases
he likelihood that the postsynaptic neuron will fire action
potentials.
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