Page 140 - The Miracle in the Cell

THE MIRACLE IN THE CELL
(a) (b) (c) (d)

Dendrite Dendrite
Receptor
cell

Side exten-
Axon tip
sions
Body of cell
Body of cell
Axon
Axon
Body of
cell
Node of Axon
Ranvier
Axon

Central
Neuron- Myelin extension
muscle sheath
connection

Axon
terminals Axon
terminals
Muscle

Figure 7.7
NERVE CELLS
As can be seen, nerve cells have been created differently, depending on their
different duties. Two different extensions transmit signals between nerve
cells: dendrites, which receive incoming signals, and axons, which pass them
on.
a) A nerve cell with needle-like dendrites and a single axon
b) A brain cell with many dendrites and a single axon. The dendrites con-
nect to hundreds of other brain cells.
c) A motor neuron signaling a muscle cell. Generally, motor neurons have
one axon, which binds to the cell that they stimulate.
d) A spinal nerve cell, which generally has two types of extension. One
transmits the signal received from receptor cells to the body of the cell, and
the other transmits it to the brain or spine.

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