Page 224 - Anatomy and Physiology of Farm Animals, 8th Edition

Anatomy of the Nervous System / 209

Olfactory n. (I) Olfactory bulb
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Olfactory tracts
Optic n. (II)
Optic chiasm
Optic tract
Oculomotor n. (III)
Pituitary gland
Trochlear n. (IV)
Crus cerebri
Trigeminal n. (V)
Abducent n. (VI) Pons
Facial n. (VII)
Trapezoid body
Vestibulocochlear n. (VIII)
Glossopharyngeal n. (IX) Pyramid
Vagus n. (X)
Accessory n. (XI)
Hypoglossal n. (XII)

Figure 10-17. Ventral view of the bovine brain. n., nerve.

spinal nerves only in thoracic and lumbar other sympathetic ganglia outside the
regions, although the chains themselves sympathetic trunk. This second group,
extend from the cranial cervical region to collectively known as collateral or preverte-
the most caudal parts of the vertebral col- bral ganglia, are sometimes associated with
umn. The ganglia, together with the nerve the large, unpaired arterial branches of the
fibers that link them longitudinally, are abdominal aorta, after which they are usually
called the sympathetic trunk. The ganglia named, or with specific target organs.
themselves are most correctly called the No sympathetic preganglionic cell bod-
ganglia of the sympathetic trunk, although ies lie cranial to the thoracic spinal cord, so
they are also called paravertebral or sym- sympathetic innervation to head struc-
pathetic chain ganglia. Cell bodies of tures (e.g., the iris, sweat glands, salivary
many of the postganglionic sympathetic glands) arrives at its targets by traveling
neurons are found here. From the sympa- craniad in right and left bundles of fibers in
thetic trunk ganglia, the unmyelinated the ventral neck. These are the cervical
axons of postganglionic neurons reach continuation of the sympathetic trunks in
their targets either following spinal nerves the thorax. These preganglionic sympa-
or via unique autonomic nerves. thetic fibers are bound in a connective
The preganglionic axons of sympathetic tissue sheath with fibers of each vagus
nerves targeting the abdominal viscera pass nerve (cranial nerve X); the combined
through the trunk without synapsing, fibers are therefore called the vagosympa-
becoming the splanchnic nerves that project thetic trunk, readily identified dorsolateral
into the abdomen from the sympathetic to and parallel with the trachea (windpipe).
trunk. These preganglionics synapse on These preganglionic sympathetic fibers in