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Neuroscience I Test 3 > Spinal Cord Morphology > Flashcards

Spinal Cord Morphology Flashcards

1
Q

conus medullaris

A
  • inferior end of the SC that is tapered
  • attached to the end of the dural sac at the level of SV2 by the filum terminal of SC
  • exists at the LV1-2 interspace
  • N rootlets emerging from here innervate the lower sacral dermatomes with the bladder and rectum
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2
Q

spinal cord segment

A
  • portion of the cord associated with a pair of dorsal and ventral roots that form a pair of spinal Ns that will innervate sensory and motor dermatomes on the head and body
  • unilaterally, a single spinal N is formed by the fusion of one dorsal root and one ventral root
  • bilaterally, each spinal N associated with a specific spinal segment forms a pair of spinal Ns
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3
Q

where do the spinal Ns exit the SC?

A
  • first cervical N (C1) exits b/w the atlas (CV1) and the occiput
  • C8 exits in the CV7-TV1 intervertebral foramen
  • rest of the Ns exit the intervertebral foramen below their correspondingly numbered vertebrae
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4
Q

cauda equina

A
  • collection of dorsal and ventral roots which course thru the lumbar cistern before exiting at the respective level
    • lumbar cistern is an expansion of the subarachnoid space that extends from the conus medullar is to the end of the dural sac at the level of the 2nd sacral vertebrae
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5
Q

cauda equina syndrome

A
  • neurologic condition in which damage to the cauda equina causes loss of function of the lumbar plexus, (nerve roots) of the spinal canal below the termination (conus medullaris) of the spinal cord.
  • CES is a lower motor neuron lesion
  • S/S–saddle anesthesia, loss of bowel and bladder dysfunction gait disturbance, severe back pain
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6
Q

sensory dermatome C4

A

shoulders

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7
Q

sensory dermatome C6

A

thumb

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8
Q

sensory dermatome T1

A

little finger, elbow

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9
Q

sensory dermatome T4

A

nipple

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10
Q

sensory dermatome T10

A

umbilicus

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11
Q

sensory dermatome L1

A

inguinal region

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12
Q

sensory dermatome L5

A

big toe

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13
Q

sensory dermatome S1

A

little toe

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14
Q

sensory dermatome S5

A

perianal region

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15
Q

biceps brachii M DTR

A

C5-6

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16
Q

brachialis M DTR

A

C6-7

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17
Q

triceps brachii M DTR

A

C6-8

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18
Q

Ms of the hand DTR

A

C8-T1

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19
Q

quadriceps femoris M DTR

A

L2-4

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20
Q

gastrocnemius M DTR

A

L5-S2

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21
Q

scapular superficial reflex

A

C5-T1

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22
Q

epigastric superficial reflex

A

T7-9

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23
Q

abdominal superficial reflex

A

T8-12

24
Q

cremasteric superficial reflex

A

L1-2

25
Q

superficial anal superficial reflex

A

S4-Co1

26
Q

anterior spinal A

A
  • singular A located deep in the anteromedian sulcus
  • supplies most of the central gray matter and the anteromedial portion of the white matter of SC
  • disruption of blood flow leads to central cord syndrome–ischemia of the central region of the SC
27
Q

posterior spinal As

A
  • course in the postero-lateral sulci of each side
  • supply about 75% of the posterior columns
  • As along with the radicular As supply the peripheral margins of the cord
28
Q

anterior and posterior radicular As

A
  • course with the ventral and dorsal rootlets
  • segmental medullary As supply the SC via the small anterior and posterior radicular branches of the ascending cervical, intercostal, and lumbar As
29
Q

anterior A of Adamkiewicz

A
  • arises from the left inferior intercostal or superior lumbar As
  • contributes to the anterior spinal A
  • major supply to the inferior 2/3 of the SC
  • may be compromised secondary to thoracolumbar fracture or surgical repair of abdominal aortic aneurysms (AAA)
30
Q

ischemic necrosis o the SC

A
  • blood supply to the cervical and lumbar enlargements is consistent
    • however, trauma to the SC may interrupt the blood supply to the cord, especially in the vulnerable regions served by 2 arterial supplies
  • causes: partial or complete transection of the SC
  • areas most involved are adjacent to enlargements at C2-3, T1-4, and L1
31
Q

gamma efferent pathway

A
  • controls the muscle tone and proprioception
  • key neuron is the gamma motor neuron located in the SC
    • influenced by descending info from the reticular formation and receive input from basal ganglia and cerebral cortex
    • output leaves SC–>courses in spinal N–>terminates in specialized M fibers (intrafusal) in the neuromuscular spindles
32
Q

intrafusal M cells

A
  • found in the gamma efferent pathway
  • control the amount of tension and, therefore, sensitivity of the neuromuscular spindles
    • tighter spindles are more sensitive to being stretched
  • info from spindles is conveyed to SC via type 1a sensory fibers
  • participate in myotatic reflex–results in activation of the motor unit that innervates some of the striated (extrafusal) M cells
  • results in inc in M tone
33
Q

alpha and gamma neurons

A
  • they are LMNs
  • they innervate M
  • a single axon from an alpha motor neuron may innervate a variable number of M cells
    • neuron and myofibers it innervates is a motor unit
  • alpha and gamma motor neurons influenced by reflexes and descending tracts from brain–coactivation
34
Q

what is the net result of the gamma efferent pathway?

A
  • alteration in M tone and reflexes
  • maintenance of accurate proprioceptive output from neuromuscular spindles
    • both hypertonia and hypotonia result in a decrease in degree and accuracy of movement performed by an affected M and a change in reflex activity
35
Q

increased gamma motor activity results in…

A

corresponding increase in M tone or hypertonia as well as hyperreflexia

36
Q

decreased gamma motor activity results in…

A

corresponding reduction of muscle tone or hypotonia and hyporeflexia

37
Q

substantia gelatinosa

A
  • sensory nuclei
  • location: posterolateral top of the dorsal horn at all spinal levels
  • function: pain and temp pathway
  • sends fibers to: lateral spinothalamic tract (LSTT)
38
Q

nucleus proprius

A
  • sensory nuclei
  • location: mid portion of the dorsal horn
  • function: pain and temp pathway
  • sends fibers to: fasciculus proprius
39
Q

nucleus dorsalis (Clarke’s column)

A
  • sensory nuclei
  • location: base of the dorsal horn from C8-L2
  • function: unconscious proprioceptive pathway
  • sends fibers to: dorsal spinocerebellar tract (DSCT)
40
Q

visceral afferent nucleus (VAN)

A
  • sensory nuclei
  • location: T1-L2 and S2-4
  • function: visceral sensory integration and reflex center
  • sends fibers to: intermediolateral gray, ventral horn, and hypothalamus via the fasciculus proprius of the reticular formation
41
Q

intermediate gray (IG)

A
  • sensory nuclei
  • location: b/w dorsal and ventral horns at all spinal levels
  • function: sensorimotor integration center
  • sends fibers to: ventral horn
42
Q

medial motor cell column (MMCC)

A
  • motor nuclei
  • location: medial part of ventral horn, all levels of SC
  • innervates: axial musculature
43
Q

lateral motor cell column (LMCC)

A
  • motor nuclei
  • location: lateral part of ventral horn in the regions of the cervical and lumbosacral enlargements
  • innervates: Ms of extremities
    • ventrolateral area–proximal limb musculature
    • dorsolateral area–distal limb musculature
    • retrodorsolateral area–intrinsic Ms of the feet and hands
44
Q

phrenic nucleus

A
  • motor nuclei
  • location: C3-5, subdivision of the MMCC
  • innervates: respiratory diaphragm
45
Q

spinal accessory nucleus

A
  • motor nuclei
  • location: C1-6 continuous with the nucleus ambiguus in the medulla
  • innervates: SCM and trapezius M
46
Q

intermediolateral nucleus

A
  • motor nuclei
  • location: lateral horn from T1-L2
  • innervates: sends preganglionic sympathetic fibers to visceral structures
47
Q

sacral autonomic nucleus

A
  • motor nuclei
  • location: lateral horn from S2-4
  • innervates: sends preganglionic PS fibers to bowel and bladder
48
Q

short ascending fibers

A
  • of the posterior column
  • with the crude tactile pathway
  • primary neurons ascend for a number of segments in posterior columns and terminate on 2ndary neurons scattered throughout the base of the dorsal horn and intermediate gray
  • axons from the 2ndary neurons form the contralateral VSTT for conveying passive touch and pressure info to the thalamus
49
Q

long ascending fibers

A
  • primary neurons of the posterior column
  • extend from level of entrance into the SC up to the level of the medulla
  • these ascending fibers form the fasciculus gracilis and fasciculus cuneatus which terminate in the corresponding nuclei in the medulla, nucleus gracilis, nucleus cuneatus
50
Q

fasciculus gracilis

A

-convey proprioceptive and 2 pt tactile sensations from lower extremities and body up the T6 sensory dermatome

51
Q

fasciculus cuneatus

A
  • located b/w postern-intermediate and posterolateral septa of SC and medulla
    • in medulla, terminates in nucleus cuneatus
  • conveys proprioception and 2 pt tactile sensations from the ipsilateral upper extremity and trunk (down to T6)
  • forms part of the posterior column/medal lemniscal system
52
Q

fasciculus proprius

A
  • surrounds the periphery of the gray matter of the SC
  • retains its role as a sensorimotor integrator of intersegmental reflexes
  • reticulospinal and spinoreticular tract (slow pain pathway) are embedded in the fasciculus proprius
  • fasciculus proprius is continuous with the brainstem reticular formation, dorsal thalamus, hypothalamus
53
Q

lateral spinothalamic tract

A
  • conveys pain and temp info
  • major clinical tract from secondary neurons in the substantia gelatinous and nucleus proprius
    • secondary axons from the nuclei cross in the anterior white commissure within 2 segments of the entrance of the original stimulus
  • terminates in the ventral posterior lateral (VPL) nucleus of the thalamus
54
Q

ventral spinothalamic tract (VSTT)

A
  • conveys light touch, pressure, and crude tactile info
  • originates from secondary neurons in the nucleus proprius and intermediate gray
    • secondary axons from these nuclei decussate in the anterior white commissure of the SC and ascend int he anterior funiculus as the VSTT
  • joins with the LSTT and spinotectal fibers in the medulla to form the spinal lemniscus
    • spinal lemniscus terminates in the VPL nucleus
55
Q

lateral corticospinal tract (LCST)

A
  • originates from neurons in the motor cortex of the cerebral hemispheres
  • descends thru the corona radiate, internal capsule, pons, and upper medulla
  • in lower medulla, most of the corticospinal fibers decussate and form the LCST
    • in the SC, LCST descends in the lateral funiculus and terminates in anterior horn and intermediate gray in all spinal levels
56
Q

anterior corticospinal tract (ACST)

A
  • formed by the 10-15% of the corticospinal fibers that did not cross at the pyramidal decussation in the lower medulla
  • in the SC, they course in the anterior funiculus
  • at their respective levels of termination, the fibers of the ACST cross in the anterior white commissure and terminate on LMNs and neuronal pools in the anterior horns and intermediate gray
57
Q

lateral reticulospinal tract (LRST)

A
  • originates in a group of medullary reticular nuclei
  • consists of both uncrossed and crossed fibers which descend adjacent to the spinal gray in the anterolateral funiculus
  • terminates in the intermediate gray of all levels of the SC
  • considered to be the principal descending pathway for autonomic responses

Neuroscience I Test 3 (20 decks)

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