Nervous System
I. Anatomical
1. Nerves: cells that carry electrical messages all over the body
2. Neuron: individual nerve cell
A stimulus excites the dendrites ---- cell body (nucleus) ----- axon(carries the
impulses) away from the cell body --- myelin sheath (a fatty tissue covering the
axon)
a. Schwann cell: cell that makes up the myelin sheath
b. White matter: nerve fibers covered in myelin
c. Grey matter: nerve fibers not covered in myelin
d. Synapse: space between each neuron
e. Ganglion: knotlike mass of neuron cell bodies located outside the CNS
3. Acetylcholine: chemical released in the body that activates the nerves and allows
transmission of a message from one nerve to the next.
II. Nervous System Divisions:
A. Central Nervous System (CNS)
1. brain – encephala
2. spinal cord – myel
B. Peripheral Nervous System
12 cranial nerves, spinal nerves that spread throughout the body
1. Autonomic Nervous System: peripheral nerves that carry nerve fibers to the
glands, heart, blood vessels, and involuntary muscles.
a. Sympathetic nervous system: “fight vs flight”
stimulated under stress or a crisis; release of epinephrine
b. Parasympathetic nervous system: “day to day” living
2. Efferent (motor) nerves: carries impulses away from the CNS to the muscles
and glands
3. Afferent (sensory) nerves: carries impulses from sensory receptors to the CNS
4. Associative nerves: nerves that carry impulses from one neuron to the next
neuron
C. Divisions of the brain based on location
1. Frontal: cranial lobe that controls the motor function
2. Parietal: middle lobe that receives and interprets sensory nerve impulse
3. Occipital: most caudal lobe that controls vision
4. Temporal: lateral lobes that control hearing and smell
D. Divisions of the brain based on function
1. Cerebrum: largest part of the brain; carries out higher brain function; receives
and processes stimuli; initiates voluntary movement; stores information
a. Cerebral cortex: outer tissue of the cerebrum
2. Cerebellum: second largest part of the brain; aids in coordination of voluntary
movements, balance and muscle tone
3. Brainstem
a. Pons: bridge for the nerves to control opposite side of the body
b. Medulla oblongata: connects the spinal cord with the brain; regulates
respiration, cardiac, and basic life functions
c. Midbrain: responsible for visual and auditory reflexes, posture, and
muscle control
d. Interbrain
1. Pituitary gland: the master gland
2. Hypothalmus: controls emotion, sleep, appetite, and regulates
hormones
3. Thymus: receives impulses from pain, touch, and temperature
4. Cerebrospinal Fluid (CSF) : clear fluid that protects, nourishes, cools, and
cushions the CNS
5. Meningies: 3 layers of connective tissue that surround the brain and spinal
cord
III. Vocabulary
1. Depression: unresponsive to the environment
2. Stupor: asleep unless aroused by a strong stimulus
3. Paralysis: complete loss of motor activity
4. Paresis: partial loss of voluntary motor activity
5. Ataxia: lack of coordination
6. Tremor: small, rapid, alternating movements at rest
7. Nystagmus: rhythmic movement of the pupils
8. Plexus: intersecting peripheral nerves
9. Coma: loss of consciousness; unresponsive to stimuli
IV. Pathological Conditions
1. Epilepsy: recurring seizures (disorganized messages in the brain)
2. Spina Bifida: congenital defect of the spinal column where the spinal canal does not
close over the spinal cord.
3. Middle Ear Infections: can cause paralysis or head tilt due to the pressure on the
facial nerve
4. Rabies: viral disease that attacks the CNS
5. Roaring: paralysis of the muscle that opens the larynx; common in race horses
6. Meningitis: inflammation of the meninges caused by a virus or bacteria
7. Hydrocephalus: accumulation of CSF on the brain
8. Radial nerve damage: trauma to the shoulder area where the limb will drag as if
broken
9. Downer cow: postpartum cow that cannot stand due to injury to the pelvis nerves
10. Schiff-Sherrington Syndrome: hyperextension of the forelimb with lesions on the
spinal cord; poor prognosis
11. Vestibular Disease: neurologic/middle ear disorder causing head tilt, nystagmus,
motion sickness, stroke like symptoms; idiopathic
12. Horner’s Syndrome: injury of the cervical nerves of the eye; sinking of the eye,
ptosis of the upper eyelid, pupil constriction, prolapsed 3rd eyelid