Outline-3, BIO 2310, Spinal Cord and Spinal Nerves


A. General function

Carry messages to and from brain, spinal reflexes

B. Location

Vertebral foramen; foramen magnum to about L2

C. Spinal Nerves

-Cauda equina

Inferior spinal nerves resembling a horse’s tail

D. Cervical & Lumbar Enlargements

E. Meninges

Protective membranes of CNS. Meninx is singular.

1. Dura mater

Outermost membrane, dense.

-Epidural space

Most epidural anesthetics are given at L2

2. Arachnoid

Middle spider web-like layer

-Subarachnoid space

Location of CSF

3. Pia mater

Innermost delicate layer

F. Gray Matter

1. Central Canal

Contains CSF

2. Posterior (dorsal) horns/Anterior (ventral) horns

Dorsal is sensory pathway, ventral is motor pathway

3. Dorsal/Ventral nerve fibers

G. White Matter

1. Columns (Anterior, Posterior, Lateral)

2. Ascending tracts (sensory) {Cross}

3. Descending Tracts (motor) {Cross} U.M.N.– Upper motor neurons

H. Spinal Reflex Arc

1. Definition ofreflex

Automatic, stereotyped reaction to a stimulus such that a particular stimulus always elicits a particular response.

2. Receptor

3. Sensory (afferent) neuron

4. Spinal cord

5. Motor (efferent) neuron L.M.N.

6. Effector

7. Somatic, Autonomic Reflexes

Somatic reflexes have skeletal muscle as effectors, autonomic reflexes have smooth muscle, cardiac muscle or glands as effectors.

8. Monosynaptic

9. Polysynaptic

a. Ipsilateral (Flexor)

Also known as withdrawal reflex

b. Contralateral (Crossed Extensor)

I. Spinal Nerves

31 pair, Spinal nerves are mixed with sensory and motor pathways.

1. Dorsal and Ventral Roots

Near the spinal cord, the spinal nerve splits into a dorsal root which carries sensory information in to the spinal cord and a ventral root which carries motor information out of the spinal cord.

2. Dorsal and Ventral Rami

Branching of spinal nerve once it emerges from intervertebral foramen.

3. Plexuses

Network of adjacent spinal nerves

a. Cervical (C1-C4-5)

1. Phrenic Nerve

Innervates diaphragm

b. Brachial (C5-T1)

1. Radial

Innervates arm and forearm extensors

2. Musculocutaneous

Innervates elbow flexors

3. Ulnar

Innervates flexors of wrist, fingers medial side

4. Median

Innervates flexors of wrist, fingers lateral side

c. Lumbar (T12/L1-L4)

1. Femoral

Innervates thigh flexors and knee extensors

d. Sacral (L4-S4)

1. Sciatic

Innervates posterior thigh, leg and foot