BIOL 351 - Spinal Cord/Nerve Plexuses

Where does the spinal cord end?

L1-L2

3 things spinal meninges provide

protection, physical stability, shock absorption

characteristics of dura mater

1. tough and fibrous

2. Continuous with brain dura

3. Outer surface is not bound to vertebrae

Epidural space

between dura and bony vertebrae

arachnoid mater

narrow subdural space that separates dura from deeper meningeal layers

What separates the arachnoid mater from the pia mater?

subarachnoid space

What fills the subarachnoid space?

cerebral spinal fluid

pia mater

innermost layer, where blood vessels supplying the spinal cord are

conus medullaris

tapered conical termination of spinal cord

filum terminale

fiber consisting of pia mater extending from conus to coccyx

purpose of filum terminale

prevent superior movement of spinal cord

spinal cord enlargements

area concerned with sensory and motor innervation of limbs

interneurons

coordinate information from sensory to motor neurons

cervical enlargement

nerves to pectoral girdle and upper limbs

lumbar enlargement

nerves to pelvis and legs

gray matter

butterfly shape in the center of the cord; cell bodies of neurons and glial cells

white matter

around the outside of gray matter; myelinated and unmyelinated axons

nuclei

groups of cell bodies of neurons in the gray matter of spinal cord

sensory nuclei

receive and relay sensory info from peripheral receptors such as touch receptors located in the skin

motor nuclei

issue motor commands to peripheral effectors such as skeletal muscles

somatic nerves

pertaining to the control of skeletal muscle activity or sensory information from skeletal muscles, tendons, and joints

visceral nerves

pertaining to the control of functions, such as digestion, circulation, or sensory information from visceral organs

dorsal gray horns

contain somatic and visceral sensory nuclei

ventral gray horns

contain neurons concerned with somatic motor control

lateral (intermediate) gray horns

contain visceral motor neurons (between T1 and L2)

31 pairs of spinal nerves

1. 8 cervical

2. 12 thoracic

3. 5 lumbar

4. 5 sacral

5. 1 coccygeal

How are cervical nerves named?

from the vertebrae immediately following them (C1 exits between skull and C1 vertebrae)

Where is the transition in naming spinal nerves?

between last cervical and first thoracic (C7-T1 nerve is C8)

How are nerves named after the transition?

They are named from the vertebrae above them (T1 exits below T1 vertebra)

central nervous system

brain and spinal cord

upper motor neurons

neurons whose cell bodies are in the brain or spinal cord and synapse with lower motor neurons

lower motor neurons

neurons with cell bodies in the ventral horn of spinal cord gray matter

What do lower motor neurons do?

initiate movement and skeletal muscle contraction

What are the 2 roots of nerves?

dorsal/sensory and ventral/motor roots

dorsal root ganglia

where cell bodies of sensory neurons are found; every spinal segment has a pair

ganglia

collection of nerve cell bodies outside of CNS

preganglionic fibers

axons extending from the CNS to a ganglion

postganglionic fibers

axons connecting the ganglion cells with peripheral effectors

dorsal rami

provide sensory info from and motor innervation to skin/muscles of neck and back

ventral rami

provides sensory and motor ventrolateral body surface, structures in the body wall, and the limbs

dermatome

pair of spinal nerves that monitors a specific region of the body surface

nerve plexus

composed of ventral rami of adjacent spinal nerves that blend their fibers to produce a series of compound nerve trunks

3 nerve plexuses

cervical, brachial, and lumbosacral

Nerves of cervical plexus

C1-C5

What nerves of the cervical plexus go to diaphragm?

Phrenic nerve; C3-C5

Nerves of brachial plexus

C5-T1

Where is the brachial plexus found?

In cervical enlargement

What does the brachial plexus innervate?

Pectoral girdle and upper limb

5 divisions of the brachial plexus

Roots, trunks, divisions, cords, branches

5 major nerves of the brachial plexus

axillary, radial, musculocutaneous, median, ulnar

Where does the lumbosacral plexus arise from?

Lumbar-ventral rami of T12-L4, Sacral-ventral rami of L4-S4

3 major nerves of the lumbosacral plexus

femoral, obturator, sciatic