Chemistry Reference
In-Depth Information
FIGURE 20.2
Structure of typical mammalian neurons. Arrows indicate the direction of conduction of the action potential in the neurons
(red). (a) Multipolar interneurons. Each has profusely branched dendrites (which receive signals at synapses with several hundred other
neurons) and a single long axon which branches laterally at its terminus. (b) A motor neuron which innervates a muscle cell. Typically, motor
neurons have a single long axon extending from the cell body to the effector cell. In mammalian motor neurons, an insulating sheath of myelin
covers all parts of the axon except the nodes of Ranvier and the axon terminus. (c) A sensory neuron in which the axon branches when it leaves
the cell body. The peripheral branch carries the nerve impulse from the receptor cell to the cell body. The central branch then carries the impulse
from the cell body, located in the dorsal root ganglion close to the spinal cord, either to the spinal cord or to the brain.
(From Lodish et al., 1995.
Copyright 1995 with permission from Scientific American Books.)
+50 mV
Action
potential
-60 mV
Time
2 ms
FIGURE 20.3
The observed membrane potential across the plasma membrane of a presynaptic cell.
