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:
-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
-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
-Synapse: junction where information is transmitted from one
neuron to another.
-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
-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
-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
-Presynaptic neuron: neuron that sends a signal across the
-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
-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