The H or "butterfly" shape
,
•
Ventral horn-larger
•
Dorsal horn-smaller

Ventral horn:
•
contains
the large somata of autonomic
motor neurons
.
•
They receive input from integrator neurons
in the cord, and
send commands to contract
to skeletal muscle in the periphery
.
Dorsal horn:
•
contains neuron somata of the connector
neurons (not motor)
.
•
They receive input from sensory fibers
entering the cord
through the dorsal root
of the spinal nerve.







The Leptomeninges
•
Surround the brain and the spinal cord.
•
The cerebrospinal fluid circulates between 2 meningeal layers
called the pia matter and the arachnoid (or pia-arachnoid
membranes).
•
The outer, thicker layer serves the role of a protective shield and is
called the dura matter.
•
The spinal cord is also covered, like the brain, by the pia matter and
the arachnoid membranes.
•
The cerebrospinal fluid circulates around the pia and below the
outer arachnoid, and this space is also termed the subarachnoid
space.
•
The dura surrounds the pia-arachnoid of the spinal cord, as it does
for the brain.
•
in spinal cord there is space between the dura mater and the vertebral
canal is the epidural (or peridural) space, filled with adipose tissue and it
contains a network of blood vessels.

CSF
subarachnoid
space.





The peripheral nervous system



Constituents of peripheral
nervous system
1. Sensory neurons,
2. Ganglia (clusters of neurons)
3. Plexuses: felt works of nerve fibres
4. Nerves
and
nerve roots.
12 pairs of cranial nerves
31 pairs of spinal nerves
Nerve Roots
A nerve root
is the
initial segment of a nerve leaving the
central nervous system.
1. A cranial nerve root,
the beginning of one of the twelve
pairs leaving the central nervous system from the brain stem
or the highest levels of the spinal cord;
2. A spinal nerve root
, the beginning of one of the thirty-one
pairs leaving the central nervous system from the spinal
cord.

•
Each spinal nerve root consists of the union of a
sensory dorsal root and a motor ventral root.
•
The dorsal root
(or posterior root) is the
afferent sensory
root of a spinal nerve.
•
The ventral root
(anterior root: is the
efferent motor
roots of a spinal cord.
•
At its distal end
, the ventral root joins with the dorsal root
to form a mixed spinal nerve.
•
Mixed (motor and sensory) peripheral nerve:
•
Fibers that carry motor input to limbs and fibers that bring
sensory information from the limbs to the spinal cord



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- Fall '16