Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

C h a p t e r
THE NERVOUS
SYSTEM
The brain comprises the cerebrum, cerebellum, midbrain, and brain stem.
The cerebrum is the largest part of the brain, and is the center of learning,
memory, sensory input, behavior, and voluntary movement. Diseases affecting
the cerebrum are characterized by depression, alterations in personality and
behavior, and seizures.
The cerebellum has two lobes. Its primary functions are to integrate motor
pathways, coordinate movements, and maintain balance. Diseases of the cerebellum
result in lack of coordination, unstable gait, and muscle tremors.
In the midbrain and brain stem are the centers that control the respiratory
rate, heartbeat, blood pressure, and other vital functions. At the base of the
brain and closely connected to the midbrain and brain stem are the hypothalamus
and pituitary glands. These structures are important in regulating the
dog’s body temperature and hormone systems. They are also the centers for
primitive responses such as hunger, thirst, anger, and fright.
The spinal cord passes down a bony canal formed by the arches of the vertebrae.
The cord sends out nerve roots that combine with one another to form
the peripheral nerves. Diseases of the spinal cord produce varying degrees of
weakness and paralysis.
The cauda equina is the termination of the spinal cord. Diseases of the
cauda equina can produce paralysis of the tail, loss of bladder and bowel control,
and paralysis of the anal sphincter.
The paired cranial nerves, 12 total, arise from the midbrain and brain stem
and pass directly out into the head and neck through openings in the skull.
The optic nerves to the eyes, the otic nerves to the ears, and the olfactory
nerves to the nasal cavity are examples of paired cranial nerves.
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