Neuro: Lecture 10 - SC Flashcards by Chavez Girls

What vertebral level does the spinal cord end?

L1-L2

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What is the difference between the filum terminale and the cauda equina?

filum terminale is a bundle of CONNECTIVE tissue

cauda equina is a bundle of NEURAL tissue

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what is the difference between the dura mater at the brain versus the spinal cord?

brain: dura connected to skull

spinal cord: dura mater NOT connected to vertebrae

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what is the difference between spinal anesthesia and epidural anesthesia?

spinal anesthesia: injected into subarachnoid space

epidural anesthesia: injected into epidural space

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what is the most lateral aspect of the CNS?

spinal nerve

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what structure starts the PNS?

rami

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where do the ventral nerve rootlets exit the spinal cord?

anterolateral sulcus

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what fibers make up the medial dorsal rootlets?

1a and A-beta - fine touch and proprioception

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what fibers make up the lateral dorsal rootlets?

A-gamma and C - pain and temperature

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denticulate ligament

anchors the SC to the dura mater

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what passes through the ventral median fissure?

anterior spinal artery

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Where does the posterior spinal artery pass through?

dorsolateral sulcus

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propriospinal tract

tract that stays within the spinal cord (originates and terminates within spinal cord)

surrounds grey mater

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tract cells

long axon cells that carry info connecting brain and SC

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What is the somatotrophic organization of the white mater in the SC medial to lateral?

cervical, thoracic, lumbar, sacral

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Which Rexed Laminae carry sensory info?

I-V

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Which Rexed Laminae carry motor info?

VIII and IX

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Substantia Gelatinosa of Rolando

Rexed Lamiae II - pain and temperature

spinothalamic tract synapses here

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Clarke’s nucleus

Rexed lamiane VII - proprioceptive information to the cerebellum via the dorsal spinocerebellar tract.

T1-L3

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Where are the cell bodies of the preganglionic sympathetic neurons located?

T1-L2

grey mater of lateral horn

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Where are the cell bodies of the preganglionic parasympathetic neurons located?

S2-S4

grey mater lateral horn

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what is the parent structure of the radicular arteries

segmental arteries

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What layer of meninges does the CSF circulate between?

Subarachnoid

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With flexion of the spine, the SC stretches __% wereas the cauda equina ____

Spinal Cord stretches 10%

Cauda Equina stretches very little

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what structures provide protection for nerve roots and spinal nerves?

fat, dural covering, and denticulate ligaments

_________ motions increase intervertebral pressure at all levels

cervical

What tract is the only one which doesn't get it's signals modulated by the spinalcord, and instead ascends all the way to the medulla before synapsing

Dorsal Column

How does the Jendrassik maneuver alter the DTR

Decreases inhibition going down the spinal cord (increases descending motor input)

What is the purpose of central pattern generator

Rhythmic motor patterns - walking, breathing, swimming, crawling, swallowing, urinating, ejaculating

stepping pattern generators

type of central pattern generator that controls the rhythm and coordination of stepping gait by alternating flexor/extensor LMN activation

With complete transection of spinal cord, the Stepping pattern generator (Central pathway generator) can only be activated by ____________

Artificial means -ex: treadmill

what is the phasic stretch reflex?

a monosynaptic reflex - does NOT involve interneurons -DTRs: fast muscle stretch activates signals from muscle spindles alpha motor neurons of the same muscle

what is the cutaneous withdrawal reflex?

a polysynaptic reflex - involves excitatory interneurons occurs in response to pain/noxious stimuli

What is the crossed extension reflex?

polysynaptic reflex - interneurons Withdraw reflex of one leg will ilicit the opposite LE to extend and catch yourself before you fall

reciprocal inhibition

inhibitory interneuron when a muscle contracts, its opposing muscle is inhibited

recurrent inhibition

inhibition of agonists and disinhibition of antagonists --> regulates fine motor control *opposite of reciprocal inhibition

What is a Renshaw cell?

Inhibitory interneuron who inhibits agonist and disihibits antagonist to promote fine motor control Opposite of a muscle spindle!

segmental vs vertical tract impairment

segmental - show dermatomal/myotomal pattern vertical pattern- everything below the level of that lesion (ipsilateral or contralateral depending on the tract)

effect of sympathetics on urination

Holds urine bladder relaxation internal urethral sphincter constriction

effect of parasympathetics on urination

releases urine bladder contraction internal urethral sphincter relaxation

Reflexive bladder function requires what spinal levels?

Afferents: T11-L2 + S2-S4 cord levels

The frontal cortex inhibits the _____ from telling sacral urination center to empty

Pons

If the situation is appropriate the ______ disinhibits the ___ which will then signals to the sacral cord center to contract bladder walls

Frontal cortex disinhibits the pons

The sacral cord center signals _______ (parasympathetic or sympathetic) neurons to contract the bladder wall and relax the sphincter

Parasympathetic

Though the pons does not inhibit the bladder wall, it does send inhibitory signals to the __________

Alpha motor neurons of the external sphincter and pelvic floor muscles

Bladder filling is involuntary with _______ (sympathetic or parasympathetic) fibers telling the bladder wall to relax and the internal sphincter to contract

sympathetic Parasympathetic does the opposite (Contracts bladder wall and relaxed sphincter)

How is the walking Stepping Pattern Generator normally activated?

Brain sends signal down spinal cord to let it know to start walking

if there is an injury AT S2-S4, what happens to the bladder?

it becomes flaccid (areflexive bladder) - bladder overfills/leaks

what happens to the bladder if there is an injury ABOVE S2-S4

bladder becomes hypertonic (hyper-reflexive) -bladder empties at even the slightest stretch

Where are psychogenic (erotic thoughts) mediated?

L1-L2 by sympathetics

Where are the reflexogenic (sensory stimulation) fibers mediated?

S2-S4 by afferents and parasympathetics

What is the location of sympathetic nerve fibers responsible for orgasm

sympathetic nerve fibers that originate in L1-L2 and pudendal nerve with cell bodies in S2-S4

in a complete SC injury, what male genital functions will be absent?

genital sensation

in a complete SCI above T12, what male genital functions will be present?

reflexive erection and ejaculation are possible

in a complete SCI between L2-S2, what male genital functions will be absent?

likely to have normal sexual function

in a complete SCI AT S2-S4, what male genital functions will be absent?

they will be impotent

What is the difference between segmental impairments and vertical tract impairments?

segmental: lesion that affects a single level of the spinal cord - dermatomal/myotomal signs vertical tract: lesion interrupting vertical tracts - ipsilateral and/or contralateral deficits BELOW the level of lesion

What is Brown-Sequard syndrome

Hemicord syndrome - Exactly 1 half of the spinal cord is cut due to gunshot or stab wound

In Brown-Sequard syndrome, the dorsal column senses are affected (contralaterally/ipsilaterally) Whereas the anteriolateral cord senses are effected (contralaterally/ipsilaterally)

Dorsal- Ipsilateral (note motor tracts are ipsilateral too) Anteriolateral - Contralateral (Because this tract crosses immediately in the spinal cord)

what are the affects of a L hemicord syndrome?

L DCML --> L loss of proprioception and light touch L corticospinal --> L loss of motor function R spinothalamic --> R loss of pain and temp

Anterior cord syndrome

MOI: flexion injury disrupted blood flow in the anterior spinal artery --> affects anterior 2/3 if the spinal cord

How does anterior cord syndrome usually present?

Motor, Nociceptive, Temperature Impairments *spinothalamic and corticospinal tract affected

What functions are typically preserved in anterior cord syndrome?

DCML - Proprioception and light touch

Central cord Syndrome

incomplete SCI where the center of the spinal cord is impaired

what is the difference between a small and large lesion with central spinal cord syndrome?

small lesions: impaired nociception and temperature at the level of the lesion large lesion: impaired nociception and temperature + UL MOTOR IMPAIRMENT

why is nociception and temperature impaired in central cord syndrome

the spinothalamic tract crosses at midline

mnemonic for central cord syndrome

M: motor loss > sensory loss U: UL > LL D: distal > proximal E: extension (MOI)

How and where does central cord syndrome usually occur?

Usually seen at cervical level following trauma

cauda equina syndrome

damage to the lumbar and/or sacral spinal roots causes sensory impairments and flaccid paresis/paralysis of the lower limb muscles, bladder, and bowel

in cauda equina syndrome,