Transcript Nervous System: Cranial nerves

Objectives
1. Review: Be able to label and identify the
function of the cranial nerves
2. List and define disorders of the nervous
tissue
3. 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
smell
2. 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 CNS
1. Skull
2. 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 impulses
5. Spinal cord – gray and white matter do NOT
intermingle; gray matter forms the interior of the
cord and white matter surrounds it
6. 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 control
7. Reticular formation
8. Pons – part of brainstem; consists of
white matter and scattered bits of gray
matter; influences respiration
9. Pituitary gland – endocrine gland that
secretes many important hormones
10. 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