50+ Lifestyles

Health Minute With CASI: The Amazing Brain – Part 4

Spinal and Cranial nerves are the most exciting part of this whole series!

There are 12 cranial nerves. They supply primarily the head and neck, except the vagus nerve (which travels to the heart, respiratory muscles, stomach, and gallbladder.) The 31 pairs of spinal nerves arise from the spinal cord and supply the rest of the body. They are named for the regions of the spine from which the exit. 8 cervical, 12 thoracic, 5 lumber, 5 sacral, and 1 coccygeal. They all contain sensory and motor fibers. The nerves enter and exit the cord through roots-Sensory afferent fibers through posterior or dorsal roots, and motor efferent through the anterior or ventral roots.

Cranial Nerve Function

I: Olfactory Smell
II: Optic Vision
III: Oculomotor Eye movement, eyelids raise, pupil constriction, lens shape
IV: Trochlear Upward and downward movement of eye
V: Trigeminal Mastication muscles
VI: Abducens Lateral eye movement
VII: Facia Facial muscles, close eye, labial speech, taste (2/3’s of anterior tongue),
Saliva and tear secretions
VIII: Acoustic Hearing and equilibrium
IX: Glossopharyngeal Phonation and swallowing, taste (1/3 of posterior tongue), pharynx (gag refex),
parotid gland, carotid reflex
X: Vagus Pharynx, and Larynx (talking and swallowing), sensation from carotid body,
carotid, sinus, pharynx, viscera
XI: Spinal Trapezius and sternomastois muscles
XII: Hypoglossal Movement of tongue

The nerves exit the spinal cord on an orderly ladder. Each nerve innervates a particular segment of the body.
Great land marks for the body:

• Thumb, middle finger and fifth finger are each dermatomes of C6, C7, and C8.
• The nipple is at the level of T4.
• The umbilicus is at the level of T10.
• The groin is in the region of L1.

Automatic Nervous System:

This nervous system is composed of cranial and spinal nerves. These nerves carry fibers that can be divided functionally into two parts-somatic and autonomic. Somatic fibers innervate the skeletal (voluntary) muscles; autonomic fibers innervate smooth (involuntary) muscles, cardiac muscle, and glands. It’s over all function is to maintain homeostasis of the body!

Your body is a temple, take care of it!