Neuro: Lecture 10 - SC Flashcards
What vertebral level does the spinal cord end?
L1-L2
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
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
what is the difference between spinal anesthesia and epidural anesthesia?
spinal anesthesia: injected into subarachnoid space
epidural anesthesia: injected into epidural space
what is the most lateral aspect of the CNS?
spinal nerve
what structure starts the PNS?
rami
where do the ventral nerve rootlets exit the spinal cord?
anterolateral sulcus
what fibers make up the medial dorsal rootlets?
1a and A-beta - fine touch and proprioception
what fibers make up the lateral dorsal rootlets?
A-gamma and C - pain and temperature
denticulate ligament
anchors the SC to the dura mater
what passes through the ventral median fissure?
anterior spinal artery
Where does the posterior spinal artery pass through?
dorsolateral sulcus
propriospinal tract
tract that stays within the spinal cord (originates and terminates within spinal cord)
surrounds grey mater
tract cells
long axon cells that carry info connecting brain and SC
What is the somatotrophic organization of the white mater in the SC medial to lateral?
cervical, thoracic, lumbar, sacral
Which Rexed Laminae carry sensory info?
I-V
Which Rexed Laminae carry motor info?
VIII and IX
Substantia Gelatinosa of Rolando
Rexed Lamiae II - pain and temperature
spinothalamic tract synapses here
Clarke’s nucleus
Rexed lamiane VII - proprioceptive information to the cerebellum via the dorsal spinocerebellar tract.
T1-L3
Where are the cell bodies of the preganglionic sympathetic neurons located?
T1-L2
grey mater of lateral horn
Where are the cell bodies of the preganglionic parasympathetic neurons located?
S2-S4
grey mater lateral horn
what is the parent structure of the radicular arteries
segmental arteries
What layer of meninges does the CSF circulate between?
Subarachnoid
With flexion of the spine, the SC stretches __% wereas the cauda equina ____
Spinal Cord stretches 10%
Cauda Equina stretches very little
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,
