has extensive neural interconnections with the CNS, it also appears to
operate with a great deal of autonomy, internally regulating its own
processes.
Connections between the CNS and the PNS are either by way of
the spinal cord or via one of twelve pairs of cranial nerves. The cranial
nerves enter and exit the brain at several points in the brainstem or,
for cranial nerve 1, via the olfactory bulbs. Here are the numbers and
names of the cranial nerves, together with something about their con-
nections and functions:
. Olfactory (nose; smell)
. Optic (retina of eye; vision)
. Oculomotor (eye muscles; eye movement, pupil constriction)
. Trochlear (eye muscles; eye movement)
. Trigeminal (face; facial sensation and movement)
. Abducens (eye muscles; eye movement)
. Facial (face; facial sensation and movement, salivation, lacrimation)
. Auditory-vestibular (inner ear; hearing and balance)
9. Glossopharyngeal (tongue and pharynx; taste and movement)
10. Vagus (pharynx, larynx, internal organs of chest and abdomen; taste,
heart rate, respiration)
11. Accessory (neck muscles; movement)
12. Hypoglossal (tongue; movement, swallowing, speech)
OAONAUFWDHSAlthough it is often convenient to partition the nervous system
into different components for ease of description and study, it is es-
sential to appreciate that all these parts are highly interconnected.
And beyond this, the nervous system is in intimate interaction
with the endocrine system, the cardiovascular system, the im-
mune system, and so forth—other bodily systems that may also
be separated out for convenience of study. The body is a highly