Objectives

1. Review: Be able to label and identify the function of the cranial nerves2. List and define disorders of the nervous tissue3. Define nerve and associated definitions 4. Be able to identify and know functions of structures shown on sagittal section of the central nervous system

Cranial Nerves

1. Olfactory nerve – nose to brain, sense of smell2. Trigeminal nerve – sensations of face, scalp, and teeth; chewing Ophthalmic branch: eye Maxillary branch: eye to upper jaw and throat Mandibular branch: lower jaw

3. Glossopharyngeal nerve – controls salivation; controls swallowing muscles; taste (posterior third of tongue); sensations of throat; blood pressure sensation

4. Hypoglossal nerve – brain to muscles of tongue; tongue movements (swallowing and speech)

5. Accessory nerve – shoulder movements; turning movements of head

6. Vagus nerve – controls swallowing muscles; control and sensation in various visceral effectors

7. Vestibulocochlear – senses of equilibrium and hearing

8. Facial nerve – controls facial muscles; controls secretion of tears and saliva; taste (anterior two thirds of tongue)

9. Abducens nerve – controls lateral rectus muscle of eye

10. Oculomotor nerve – controls upper eyelid muscles; controls ciliary muscle of the eye and sphincter (ring-shaped muscle) in the iris

11. Optic nerve – vision

12. Trochlear nerve – controls superior oblique muscle of the eye

Disorders of Nervous Tissue

Multiple sclerosis (MS) – myelin disorder: myelin loss and destruction accompanied by varying degrees of oligodendrocyte injury and death; nerve conduction impaired, speech disturbances, vision impairment, weakness, incoordination

Relapsing and chronic

Cause: autoimmunity?, viral?

No known cure

Neuroma – tumor; usually develop from glia, membrane tissues, and blood vessels

Some types of neuromas:

Glioma – common, usually benign but can still be life-threatening

Multiple neurofibromatosis – inherited; fibrous neuromas throughout the body; benign but can be disfiguring; “Elephant Man” disease

Note

Most malignant tumors of glia and other nervous tissue do not arise there but are secondary tumors resulting from the metastasis of cancer cells from the breast, lung, and other organs

Nerves

A nerve is a group of peripheral nerve fibers (axons) bundled together like the strands of a cable

Nerves usually have a white, myelin sheath so called the white matter of the PNS

Bundles of axons in CNS, called tracts, may also be myelinated: White matter of CNS

Gray matter – tissue composed of cell bodies and unmyelinated axons and dendrites

Each axon in a nerve is surrounded by a thin wrapping of fibrous connective tissue called endoneurium

Fascicles – groups of wrapped axons

Each fascicle is surrounded by a thin, fibrous perineurium

The whole nerve is covered by a tough, fibrous sheath called the epineurium

Endo---Peri----Epi

Axon---fascicle----whole nerve

Sagittal Section of the CNS1. Skull2. Pineal gland-third ventricle; produces melatonin Ventricle: cavity with cerebrospinal fluid Melatonin: hormone that regulates puberty and menstrual cycle; “third eye” (responds to light and body’s internal clock)3. Cerebellum-second largest part of brain; production of normal movements; muscle coordination, equilibrium, posture

4. Midbrain-one of the three parts of the brain stem; relay for visual and auditory impulses5. Spinal cord – gray and white matter do NOT intermingle; gray matter forms the interior of the cord and white matter surrounds it6. Medulla- enlarged upward extension of the spinal cord; bits of white and gray matter mix to form the reticular (net-like) formation; cardiac, respiratory, and vasomotor control7. Reticular formation

8. Pons – part of brainstem; consists of white matter and scattered bits of gray matter; influences respiration9. Pituitary gland – endocrine gland that secretes many important hormones10. Hypothalamus- regulation of body temperature, water balance, sleep-cycle control, appetite, sexual arousal

11. Cerebral cortex – outer part of cerebrum ( largest and most upper part of the brain; sensory perception, emotions, willed movements, consciousness, memory) Ridges called convolutions or gyri Grooves called sulci Deepest sulci called fissures Longitudinal fissure divides cerebrum into right and left halves (hemispheres)

12. Thalamus – emotions and alerting, arousal mechanisms

13. Corpus callosum – connects lower portion of the right and left hemispheres of the cerebrum