Nerves

1. NERVES

2. Nerves are not to be confused with neurons. A
“nerve” is actually a bundle of many, many neuronal
processes. It is not a cell like a neuron, rather it is a
collection of cellular parts. This means that a nerve is
a large collection of myelinated axons (but can be
myelinated “dendritic axons” in the case of sensory
neurons).
A Spinal Nerve

3. 1.Motor Nerves – These are nerves that contain only
motor nerve fibers (motor neuron axons). These
transmit messages from the CNS to the periphery.
2. Sensory Nerves – These are nerves that contain
only sensory nerve fibers (sensory neuron axons
and/or dendrites). These transmit messages from the
peripheral receptors to the CNS.
3. Mixed Nerves – These are nerves that contain both
motor and sensory nerve fibers (motor and sensory
neuron axons). These can conduct messages along
sensory axons from the periphery to the CNS or from
the CNS to the periphery.

4. Spinal Nerves
All along the length of the spinal cord 31 pairs of
spinal nerves emerge. These consist of mixed nerves
as follows:
a.8 pairs of cervical
nerves.
b.12 pairs of thoracic
nerves.
•5 pairs of lumbar
nerves.
•5 pairs of sacral
nerves.
•1 pair of coccygeal
nerves.

5. Cranial nerves
The brain communicates with
the body through the spinal cord
and twelve pairs of cranial
nerves. Ten of the twelve pairs
of cranial nerves that control
hearing, eye movement, facial
sensations, taste, swallowing
and movement of the face,
neck, shoulder and tongue
muscles originate in the
brainstem. The cranial nerves
for smell and vision originate in
the cerebrum.

6. Cranial nerves
Number Name Function
I olfactory smell
II optic Sight
III oculomotor moves eye, pupil
IV trochlear moves eye
V trigeminal face sensation
VI abducens moves eye
VII facial moves face, salivate
VIII vestibulocochlearhearing, balance
IX glossopharyngealtaste, swallow
X vagus heart rate, digestion
XI accessory moves head
XII hypoglossal moves tongue