NERVOUS SYSTEM
I. CENTRAL NERVOUS SYSTEM
A. Consists of brain and spinal cord
B. Neurons, nerve fibers (tracts)
C. Nucleus
II. PERIPHERAL NERVOUS SYSTEM
A. Cranial nerves - arises from the brain
B. Spinal nerves - arise from the spinal cord
C. Terminology
1. Neuron - soma, axon, dendrites
2. Nerve - bundle of nerve fibers or axons
3. Fascicles - bindles of nerve fibers
4. Nerve plexus - network of fibers
5. Ganglion
6. Myelin sheath
7. Synapse
8. Presynaptic
9. Postsynaptic
10. Efferent fibers
11. Afferent fibers
12. Primary rami (dorsal and ventral)
13. Dorsal root
14. Ventral root
III. AUTONOMIC NERVOUS SYSTEM - considered more later
A. Consists of three parts:
1. Sympathetic system - (fight, fright, flight)- emergency or stress
a. paravertebral ganglia - related to trunk
b. prevertebral ganglia - viscera
2. Parasympathetic system- conserve and restore resources - craniosacral
3. Enteric system - related to innervation of the gut tube
B. Innervates heart, smooth muscle and glands
C. Preganglionic fibers - w/in the CNS
D. Postganglionic fibers
E. Rami communicantes - white and gray
IV. TYPICAL SPINAL NERVE, REVIEW
A. Dorsal and ventral roots, ganglion
B. Simple reflex: review components => (see diagram on next page)
C. Spinal nerve functional components
1. somatic motor (GSE)
2. somatic sensory (GSA)
3. visceral motor-review course, rami, ganglia etc. (GVE)
4. visceral sensory (GVA)
D. Typical branches of Spinal Nerve
1. (Recurrent) Meningeal Branches-recurve through intervertebral foramen, vasomotor and sensory to spinal meninges
2. Dorsal primary ramus-to area of deep back muscles and paramedian dorsal skin
a. medial branch-mostly sensory at C & T levels, motor at lower levels
b. lateral branch-mostly motor at C & T levels, sensory at lower levels
c. always segmental
3. Ventral primary ramus
a. typical branching pattern (thoracic n.)
b. participation in plexi, particularly to neck and extremities
V. DISTRIBUTION OF DORSAL RAMI
A. Sensory-segmental generally, exceptions include
1. C1 has no cutaneous distribution
2. C2 runs superiorly to vertex
3. C3 may accompany part of C2
B. Motor - segmental to deep back and deep neck mm.
VI. DERMATOMES
A. Definition: area of skin supplied by one segmental nerve
B. Overlap - any one segment usually overlapped halfway by next higher nerve, next lower nerve
C. Important to learn dermatomes in order to help distinguish a peripheral nerve lesion from a more central lesion
D. "Marker" dermatomes
1. General:
a. C2 - back and side of scalp
b. C3 - top of shoulder
c. C4 - tip of shoulder
d. C5-T1 - upper extremity
e. T4 - nipple
f. T10 - umiblicus
g. L1-L4 - lower extremity
h. S3-S5 - perineum
2. Specific landmarks on extremities - variable
a. C5 - lateral shoulder and elbow
b. C6 - thumb
c. C7 - middle finger
d. C8 - ulnar side of hand
e. T1 - medial forearm
f. T2 - medial arm
g. L1 - anterior thigh (upper)
h. L2 - anterior mid thigh
i. L3 - knee
j. L4 - medial ankle
k. L5 - medial digits
l. S1 - plantar area
m. S2 - posterior leg and thigh
VII. LANDMARKS - TORSO (palpable structures)
A. Suprasternal notch = jugular notch = superior margin of sternum
B. Sternal angle (of Louis) - between manubrium and body of sternum (location of anterior end of rib 2)
C. Xiphisternal junction - between sternal body and xiphoid process
D. Subcostal angle - between converging ribs, below xiphoid
E. Costal margin - lower margin of rib cage
F. Clavicle
G. Anterior axillary fold
H. Posterior axillary fold
I. Spine of scapula
J. Acromion of scapula
K. Superior and inferior angles of scapula
L. Vertebra prominens = C7 spine