chapter 3 ...
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Neurons- basic building blocks of the nervous system.
o Each neuron has 3 main parts:
o Cell body or soma- contains the biochemical structures needed to keep the neuron
alive, and its nucleus carries the genetic information that determines how the cell
develops and functions. Center to process and combine messages sent by neurons.
o Dendrites- emerging from the cell body, these are branchlike fibers. They collect
messages from neighboring neurons and send them on to the cell body.
o Axon- conducts electrical impulses away from the cell body to other neurons, muscles,
Blood-brain barrier- prevents many substances, including a wide range of toxins, from entering
Action Potential- or nerve impulse is a sudden reversal in the neuron’s membrane voltage,
during which the membrane voltage momentarily moves from -70 millivolts (inside) to +40
Depolarization- this (^) shift from negative to positive.
Graded potentials- when the dendrites or the cell body of a neuron are stimulated by axons
from other neurons, small shifts occur in the cell membranes electrical potential. These changes
are called graded potentials. They are proportional to the amount of incoming stimulation.
All-or-none law- the action potential either occurs with maximum intensity or it does not occur
Ion channels- graded potentials change the membrane potential by acting on tiny protein
structures in the cell membrane called ion channels.
Refractory period- time period during which the membrane is not excitable and cannot
discharge another action potential.
Myelin sheath- tube-like, fatty, whitish insulation layer derived from glial cells during
Synapse- a functional but not physical connection between a neuron and its target.
Synaptic cleft- a tiny gap or space between the axon terminal of one neuron and the dendrite of
the next neuron.
Neurotransmitters- chemical substances that carry messages across the synapse to either excite
other neurons or inhibit their firing, produced by neurons.
Synthesis stage- chemical molecules are formed inside the neuron.
Synaptic vesicles- chambers where molecules are stored.
Receptor sites- large protein molecules embedded in the receiving neuron’s cell membrane.
Excitatory transmitters- neurotransmitters that create depolarization.
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