1. Chapter 11E Nervous System II
Anatomy and Physiology

2. Peripheral Nervous System
The peripheral nervous system is made of the nerves that branch from the CNS, connecting it to other body parts.
This includes cranial nerves that comes from the brain and spinal nerves that come from the spinal cord.

3. The PNS is subdivided into the somatic nervous system - which controls the skin and skeletal muscles, it controls conscious activities.
The autonomic nervous system connects to the heart, stomach, intestines, and different glands. It controls subconscious actions.

4. Structure of Peripheral Nerves
Nerves are bundles of axons, but they have specific levels of organization. Axons are bundled into fascicles. Each fascicle is enclosed in loose connective tissue called perineurium. A group of bundled fascicles, surrounded by dense connective tissue called the epineurium makes a nerve.
There are blood vessels in the epineurium and perineurium provide oxygen and nutrients to the neurons.

5. Nerve and Nerve Fiber Classification
Sensory nerves are nerves that have only fibers of sensory neurons, moving impulses into the brain or spinal cord.
Nerves that involve motor control are motor nerves.
Mixed nerves have both motor and sensory fibers.

6. Cranial nerves start at the brain and communicate with other body parts.
Spinal nerves start at the spinal cord and communicate with other body parts.

7. Cranial and spinal nerves can be divided into 4 groups:
General somatic efferent fibers - move motor impulses outward from brain or spinal cord to skeletal muscles and make them contract.
General visceral efferent fibers - move motor impulses from the brain and spinal cord to smooth muscle and glands in internal organs.
3. General somatic afferent fibers - move sensory impulses from the skin and skeletal muscles to the brain or spinal cord.
4. General visceral afferent fibers - move sensory impulses from blood vessels and internal organs to the brain and spinal cord.

8. The term general in the categories on the slide before tells us they are associated with general structures like the skin, skeletal muscles, glands, and viscera.
There are 3 other groups of fibers found only in cranial nerves that are specialized. They are:
Special somatic efferent fibers - move motor impulses from the brain to the muscles used in chewing, swallowing, speaking, and forming facial expressions.
Special visceral afferent fibers - move sensory impulses inward to the brain from the olfactory and taste receptors.

9. Special somatic afferent fibers - move sensory impulses to the brain from receptors of sight, hearing, and equilibrium.

10. Cranial Nerves
There are 12 pairs of cranial nerves that are on the underside of the brain.
Most of these are mixed nerves, but some are associated with special senses - like smell and vision.
We will look at what each pair of cranial nerves does.
Olfactory nerves - important for the sense of smell. Found in the lining of the upper nasal cavity. They move the impulse to the olfactory bulbs to the olfactory tracts to an area in the brain where they produce sensation of smell.

11. 2. Optic nerves - lead from the eyes to the brain
2. Optic nerves - lead from the eyes to the brain. They are associated with vision.
3. Oculomotor nerves - move from the brain to the orbits of the eyes. They are important for raising the eyelids and controlling four of the six muscles that moves the eye. Also controls involuntary muscles in the eyes. This will adjust the amount of light that enters the eye and help focus the lenses.
4. Trochlear nerves - the smallest nerves. They move motor impulses to the outside eye muscles.

12. 5. The trigeminal nerves are the largest
5. The trigeminal nerves are the largest. They have 3 large branches: ophthalmic division - moves impulses to the brain from the surface of the eye, tear duct, and the skin of the scalp, forehead, and upper eyelid. Maxillary division moves impulses from the upper teeth, upper gum, and upper lip. The mandibular division has motor and sensory fibers that moves impulses from the scalp behind the ear, skin of the jaw, lower teeth, lower gum, and lower lip.
6. Abducens nerves - Enter the orbits of the eyes and move motor impulses to the remaining part of the eye.
7. The facial nerves - They are related to taste receptors and some of the muscles related to facial expression. They can also stimulate tear glands and salivary glands.

13. 8. Vestibulocochlear nerves - These nerves have 2 parts - a vestibular branch and a cochlear branch. The vestibular branch is important for the inner ear. They contain receptors that sense changes in the position of the head and help maintain equilibrium. The cochlear branch is part of the inner ear that houses hearing receptors.
9. Glossopharyngeal nerves - associated with the tongue and pharynx. They help in producing some saliva and swallowing.
10. The vagus nerves - move through the neck into the chest and abdomen. These conduct impulses to the larynx and pharynx. They are important for speech and swallowing reflexes. They move impulses from the pharynx, larynx, esophagus, thorax, and abdomen to the brain.

14. 11. Accessory nerves - These have nerves that are from the brain and spinal cord. The cranial branch of these nerves joins the vagus nerves and moves impulses to the muscles of the soft palate, pharynx, and larynx. The spinal branch moves into the neck and has motor fibers to the trapezius and sternocleidomastoid muscles.
12. Hypoglossal nerves - move into the tongue. They help move the tongue for speaking, chewing, and swallowing.