spinal cord + nerves

SC general features

surrounded by meninges (loosely in vertebral canal)

extend from foramen Magnus → L1

SC ends L2-3

cervical + lumbar enlargements (innervate limbs)

conus medullaris: cone-shape termination

internal organization of SC: gray matter

core

nerve cell bodies

posterior projection: dorsal horn (sensory neurons)

anterior projection: ventral horn (motor neurons)

intermediate gray matter

connects ventral + dorsal horn in gray matter

in T region: lateral horn

visceral motor neurons

spinal nerves amount by region

C: 8

T: 12

L: 5

S: 5

Coccyx: 1

31 pairs

C1-C7 nerves emerge from

intervertebral foramina

above corresponding vertebrae

(ALL other nerves exit below corresponding vertebrae)

dorsal root ganglion contains

dorsal sensory (A)

ventral motor (E)

dorsal rami direction + function

posterior

motor innervation of deep back muscles

sensory supply of spine + skin on back

ventral rami direction + function

laterally + anteriorly

innervate muscles + skin on extremities + ventrolateral body wall

peripheral nerves composed of

nerve fibers/axons

extensions of nerve cells/neurons

nerve impulses into CNS

sensory / afferent fibers (A)

nerve impulses out of CNS

motor / efferent (E) fibers

somatic fibers (S)

nerve fibers that innervate skeletal mm, bone, joints, skin + subcutaneous T

visceral fibers (V)

nerve fibers innervating structures w/ smooth mm, cardiac mm, + glands

4 functional types of nerve fibers

general somatic afferent (sensory): somatosensory F

general visceral afferent (sensory): viscerosensory F

general somatic efferent (motor): somatomotor F

general visceral efferent (motor): visceromotor F

cutaneous branches contain

GSA + GVE fibers

(GVE innervate sweat glands, arrector pili, smooth mm in blood vessels)

nerve cell bodies located in dorsal root ganglia

GSA + GVA

GSE cell bodies located in

ventral horn

GVE cell bodies located in

intermediate gray/lateral horn of SC

motor neurons in ventral horn innervate + overview

skeletal muscles

GSE

leaves cord by ventral root (travels in peripheral N to end as motor end plates in skeletal mm)

neurons + fibers form somatic motor system

visceral motor neurons (GVE) are apart of

ANS

(in lateral horn)

ANS divisions

sympathetic: fight or flight

parasympathetic: rest + digest

spinal cord segments

portion of cord that provides dorsal + ventral root filaments to single nerve pair

31 segments + 31 nerve pairs

cauda equina

bundle of descending roots

long dorsal + ventral roots in L + S nerves

peripheral nerve distribution

Ns supply limbs are branches of plexuses

contain N fibers from several spinal nerves

(formed from a bunch spinal nerves)

segmental nerve distribution

goes to muscles, skin, + bones

myotomes + dermatomes

myotome

single ventral root + muscle it supplies

dermatome

single dorsal root + ganglion/cutaneous area of skin it supplies

dura mater

outmost + toughest layer of meninges

foramen magnum → S2

continues w/ epineurium of SN in intervertebral foramen

epidural space

separates dura mater from bony + ligamentous walls of vertebral canal

epidural anesthesia administered here

arachnoid mater

delicate membrane lining inside of dura

separated from dura by subdural space

pia mater

thin, delicate

invests surface of SC + nerve roots

extends down from SC → bottom of dural sac + attaches to coccyx

filum terminale: continuation of pia

denticulate ligaments

anchors dura to SC

2 lateral series of flattened bands of pia

what layers are bound in subarachnoid space

arachnoid

pia

(extends down to bottom of dural sac)

what is contained in the subarachnoid space

cerebral spinal fluid (CSF)

cerebral spinal fluid (CSF)

formed in brain

surround brain + SC

cushions + protects from trauma

what level does the SC end

L1-2

punctures + anesthesia performed below L2