Kin 1A03 - Spinal Cord and Spinal Nerves

vertebral column

vertebral column

all the individual vertebrae stacked on top of one another

cervical region

most superior region of spine

thoracic region

inferior to cervical region of spine

lumbar region

inferior to thoracic region of spine

sacral and coccygeal regions

most inferior regions of spine

vertebral canal

where spinal cord is located, created by stacking vertebrae

intervertebral foramen

where spinal nerves exit out

meninges

keep spinal cord in middle of vertebral canal, provide protective covering, continuous from brain

spinal cord

part of CNS, where all nerves converge

spinal cord structure

comprised of nervous tissue, extends from foramen magnum to L2

spinal cord function

provides pathway for information to travel, link between brain and PNS, integrates information and produces responses

foramen magnum

circular shaped hole at bottom of skull

spinal cord segments

cervical, thoracic, lumbar, and sacral segments

spinal cord diameter

spinal cord is not uniform in diameter, has two enlargements (cervical enlargement, lumbosacral enlargements)

spinal cord enlargements function

provide extra nervous tissue for upper and lower limbs

cervical enlargement

located between C4 and T1

lumbosacral enlargement

located between T9 and T12, nerves supplying lower limbs exit lumbosacral enlargement, travel down through vertebral canal, and exit via a foramina

conus medullaris

inferior end of spinal cord

cauda equina

extension of nerves beyond conus medullaris (hair-like nature of nerves makes structure look like a horses tail

filum terminale

extension of pia mater, anchors spinal cord longitudinally to coccyx, stops movement in superior direction

dura mater

most superficial meningeal layer, continuous with brain and epineurium of spinal nerves, made of dense irregular CT

periosteum connective tissue

found on surface of bone

epidural space

space between dura mater and bone, filled with fat, blood vessels, and areolar connective tissue, protects and holds spinal cord in place

epidural

injection many pregnant women receive during labor, anesthesia is injected into the epidural space and it blocks nerves so woman cannot feel pain

subdural space

contains small amount of serous fluid

arachnoid mater

middle, thinnest layer, avascular (doesnt have its own blood supply), contains simple squamous epithelium

subarachnoid space

contains cerebrospinal fluid

pia mater

deepest layer, tightly adheres to spinal cord, covers every bump and groove, blood vessels in this area supply spinal cord

denticulate ligaments

small extensions of pia mater, move towards dura mater between nerve roots, anchors spinal cord laterally

white matter

divided into two halves with three columns in each half

white matter columns

anterior, lateral, and posterior columns, each column is subdivided into nerve tracts

tracts

grouped based on similar function or similar target area of body, ascending and descending, allows info to be transmitted in an organized fashion

gray matter

divided into two halves with three horns in each half

gray matter horns

posterior, anterior, and lateral horns

lateral horns

autonomic nervous system, very small horn

posterior horns

sensory neurons

anterior horns

aka motor horn, motor neurons, largest horn

posterior median sulcus

shallow groove separating halves of spinal cord

anterior median fissure

deep groove separating halves of spinal cord

commissures

axons that cross from one side of spinal cord to the other, connect two sides of spinal cord (one anterior white and one gray)

central canal

found in centre of gray commissure, allows flow of CSF

roots

where nerves enter/exit the spinal cord, each has a ganglion (bulge)

anterior/ventral root

where motor roots exit

posterior/dorsal root

where sensory neurons enter

path of information travel through nerves

nerve impulse enters posterior/dorsal root, travels to ganglion, meets at spinal nerve, exits out anterior/ventral root (sensory impulse enters, motor signal exits)

spinal nerves (roots)

where dorsal and ventral roots meet, means all have a mixed function

pathway of sensory impulse

originate from receptors, carried by sensory neurons, enter spinal cord via posterior route, once in spinal cord can take several routes: can form tracts or can synapse with interneurons, can go to brain or to a motor neuron, motor - leaves through anterior route, reaches skeletal muscle destination through distribution of spinal nerves and peripheral nerves

ascending tracts of white matter

carries info travelling towards the brain, named for where they are in spinal cord (name includes region of brain where sensory info will be processed)

descending tracts of white matter

carries info travelling away from the brain, names reflect location in spinal cord (where neurons controlling activity arise/take major detours)

sensory and motor processing organization

internal anatomy of spinal cord allows sensory and motor information to be processed in an organized way, sensory neurons pass into posterior horn through dorsal root, synapse with interneurons or enter white matter and ascend or descend cord

spinal nerve pairs

31 pairs, named and numbered for where they exit the vertebral canal

first spinal nerve pair

exits vertebral column between skull and C1, superior to initial vertebrae of vertebral column

spinal nerve C1-C7

named for vertebra below them (e.g. C2 exits above vertebra 2)

spinal nerve C8

there are 7 vertebra in cervical region but 8 cervical nerves, C8 exits below vertebra C7, after C8 names of nerves are related to vertebra superior to them

exit via sacral foramina

four nerve pairs

exit via intervertebral foramina

nerve pairs exit through holes between each vertebra below them

cervical nerve pairs

eight pairs

thoracic nerve pairs

twelve pairs

lumbar nerve pairs

five pairs

sacral nerve pairs

five pairs

coccygeal nerve pairs

one pair

rootlets

6-8, merge to form 1 root, along dorsal and ventral surfaces of spinal cord, where each nerve arises from

ventral and dorsal roots

pass through subarachnoid space, pierce arachnoid and dura mater, join to form spinal nerve

dorsal roots

each contains a ganglion

damage to spinal cord

will result in characteristic loss of some sort of sensation depending on area where damage occurred, damage can result from acute injury caused by trauma or a tumor, could impact only motor function, only sensory function, or only a certain area of body

diseases associated with anterior horn of spinal cord (motor horn)

polio (caused by polio virus, attacks cell bodies of motor neurons in anterior horn), ALS (amyotrophic lateral sclerosis, attacks motor neuron cell bodies in brain and spinal cord)

nerve covering layers

endoneurium, perineurium, epineurium

endoneurium

deepest layer, around each axon, separates axons from eachother

perineurium

middle layer, around each fascicle

fascicle

group axons together, arteries and veins surround fascicles to provide blood flow to axons

epineurium

most superficial layer, around entire nerve, groups fascicles together to form nerves, becomes dura mater as you go down towards spinal cord

ramus

branch of nerve (plural = rami)

posterior/dorsal ramus

innervates deep muscles of trunk, responsible for movements of vertebral column

anterior/ventral ramus

form intercostal nerves and five plexuses

thoracic region (T2-T12)

form intercostal nerves

plexus

bundle of intermingling nerves

plexus formation

nerves coming out of spinal cord at different levels and then redistributing axons so nerves actually reaching target tissues receive info from different areas of spinal cord

ventral rami of C1-C4 (and some C5)

form cervical plexus

ventral rami of C5-T1

form brachial plexus

ventral rami of L1-L4

form lumbar plexus

ventral rami of L4-S4

sacral plexus

ventral rami of S4-S5 and Co

form coccygeal plexus

cervical plexus

most superior and one of smaller plexuses, roots in C1-C4

cervical plexus innervation

innervates superficial neck structures, skin of neck, posterior portion of head, and superior part of shoulders and chest

phrenic nerve

peripheral nerve with origins in C3-C5, innervates diaphragm

peripheral nerves

made up of complex connections of nerves

brachial plexus

roots in C5-C8 and T1

brachial plexus subunits

3 trunks, 6 divisions, 3 cords, 5 branches

mnemonic for subunits of brachial plexus

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brachial plexus branches

musculocutaneous, axillary, median, radial, ulnar, contain peripheral nerves, extend into shoulders and upper limbs

musculocutaneous branch

origins in C5-C7, innervates flexers of forearm

axillary branch

origins in C5-C6, innervates deltoid and teres minor muscles, skin over deltoid and supeiror posterior aspect of arm (muscles in shoulder involved in arm movement)

median branch

origins in C5-T1, innervates anterior forearm and hand, associated with movement of thumb

radial branch

origins in C5-T1, innervates posterior arm and forearm

ulnar branch

origins in C8-T1, innervates forearm and hand muscles

formation of brachial plecus

1. form 3 trunks 2. form 6 divisions 3. form 3 cords 4. form 5 branches

brachial plecus trunks

superior, middle, and inferior

brachial plexus cords

lateral, posterior, and medial

lumbar plexus

roots in L1-L4, minimal intermingling of fibers (not as much mixing as brachial plexus)

major peripheral nerves (supply part of lower limbs)

femoral, obturator