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Module 8 > Local Functions of the Spinal Cord Segmental Spinal Reflexes > Flashcards

Local Functions of the Spinal Cord Segmental Spinal Reflexes Flashcards

1
Q

what is an alpha efferent neuron

A

with its cell body in the ventral grey horn of the spinal cord, innervates the extrafusal muscle fibre

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2
Q

what is the gamma efferent neuron

A

its cell body in the ventral grey horn of the spinal cord, innervates the polar region of the intrafusal muscle fibre

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3
Q

what is a lower motor neuron

A

neurons associated with motor function that have their cell body in the CNS and their axon leaves the CNS in a cranial or spinal nerve to synapse via a neuromuscular junction with striated, smooth or cardiac muscle

could be considered to be peripheral motor neurons

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4
Q

what is the reflex arc

A

involves both the peripheral nervous system and the CNS

sensory/afferent nerve brings information into the CNS where the input is linked to a motor/efferent nerve that connects back to a muscle

hard-wired into nervous system

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5
Q

what is a response/reaction

A

cortically mediated

sensory/afferent info is integrated and interpreted in the cerebral cortex and a motor/efferent response is initiated as consequence

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6
Q

what is the upper motor neuron

A

neurons confined to CNS that are associated with motor function

could be considered to be central motor neurons

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7
Q

what is the anatomical pattern of UMN and LMN in the spinal cord

A
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8
Q

what are the common structures of a reflex arc

A
  1. receptor system
  2. afferent (sensory) nerve
  3. efferent (motor) nerve
  4. effector system - muscle
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9
Q
A
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10
Q

what is a muscle spindle and stretch reflex

A

fight gravity

muscle spindle –> when muscle stretches –> 1a afferent neurons carry information all the way up to the dorsal nerve root –> dorsal horn of spinal cord –> synapse on ventral gray column in gray matter –> alpha efferent neuron to extrafusal muscle fibres

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11
Q

what is the function of interneurons in the stretch reflex

A

inhibit efferent neurons that innervate antagonist muscle

inhibited alpha motor neuron to muscle fibres –> so they don’t counteract stregnth of muscle contracting

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12
Q

what happens when arc is interrupted

A

interruption with any of components –> decreased function

diminished/absent reflex

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13
Q

how can afferent/efferent sides of reflex arc be differentiated

A
  1. resting muscle tone –> decreased = efferent side

–> normal = afferent side

  1. resistance to forced extension/flexion –> decreased = either side
  2. sensation –> decreased = afferent side
  3. muscle bulk –> decreased, rapid, severe = efferent side
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14
Q

what reflexes are affected by spinal cord dysfunction

A
  1. thoracic limb
  2. pelvic limb
  3. sphincter
  4. cutaneous trunci
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15
Q

what nerves do the flexor (withdrawal) reflex test

A

sciatic nerve

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16
Q

what nerves do the patellar reflex test

A

femoral

17
Q

what nerves do the perineal reflex test

A

pudendal

18
Q

how is the patellar reflex performed

A

hold limb such that stifle is semi-flexed

percussion of patellar tendon (muscle stretch receptors)

reflex –> brisk, controlled extension of stifle

19
Q

what nerve is responsible for patellar reflex and what spinal cord segment

A

femoral nerve

spinal cord segments L4-6 (cranial aspect lumbar intumescence)

20
Q

what ist he patellar reflex pathway

A
  1. 1a afferent fibre in muscle (annulospiral receptor)
  2. efferent ventral gray column to quadriceps muscle
  3. extension of stifle
21
Q

how is the pelvic limb withdrawal performed

A

lateral recumbency

pinch digit with fingers (sensory)

varying degree of stimulus

reflex –> flexion of hip, stifle, tarsus

22
Q

what nerve is involved in the pelvic limb withdrawal and what segments of the cord

A

sciatic nerve

L6, 7, S1

23
Q

how is the perineal reflex done

A

pinch perineum on both sides

sensory receptors perineum

reflex –> contracting of the anus and clamping of tail (pudendal nerve –> anus, caudal nerves –> tail)

24
Q

what is the nerve of the perineal reflex and the spinal cord segment

A

pudendal nerve

S1-Cd5 spinal cord segments

25
Q

what is the perineal reflex pathway

A
  1. afferent sensory receptors of perineum
  2. efferent ventral gray column to anal sphincter muscle
26
Q

what is the pelvic limb withdrawal pathway

A
  1. afferent sensory from skin pinch
  2. interneuron 1: dorsal gray column to ventral gray column
  3. efferent: ventral gray column to flexor muscles
27
Q

what are the test reflexes associated with the cervical intumescence

A
  1. flexor (withdrawal): sensory –> varies with area stimulated. motor –> musculocutaneous, axillary, median, ulnar, radial
  2. biceps reflex: sensrory & motor: musculocutaneous
  3. triceps reflex: sensory & motor: radial
  4. cutaneous trunci reflex: sensory –> skin dorsal trunk (T2-L4), motor –> lateral thoracic nerve
28
Q

how is the thoracic limb reflex performed

A

lateral recumbency

pinch digit with fingers (sensory)

reflex –> flexion of carpus, elbow and shoulder

29
Q

what nerves and what segments are involved in the thoracic limb withdrawal

A

axillary, musculocutaneous, median, ulnar, radial

C6, 7, 8, T1, 2 segments

30
Q

what is the thoracic limb reflex pathway

A
  1. afferent sensory from skin on dorsal aspect of paw
  2. interneuron 1: C7-T1 dorsal to ventral horn
  3. interneuron 2: C6 to T2 dorsolateral funiculus
  4. efferent motor to flexor muscles of shoulder
31
Q

how is the cutaneous trunci reflex performed

A

pinch skin over dorsum

1 inch off midline from level of ileal wing to T2

reflex –> bilateral contraction of the cutaneous trunci muscle

32
Q

what nerve and what spinal segments are involved in the cutaneous trunci reflex

A

C8-T1 spinal cord segments

lateral thoracic nerve

33
Q

what is the cutaneous trunci reflex pathway

A
  1. afferent neurons from dermatomes –> neuron 1 from ipsilateral dorsal gray column
  2. neuron 2 (contralateral) dorsal gray column to contralateral dorsal gray column of T2
  3. neuron 3 dorsal gray column to ventral gray column of T1
  4. efferent: neuron 4 ventral gray column to cunatenous trunci muscles
34
Q

what occurs if segmental spinal limb reflexes are intact

A

upper motor neurom lesion

35
Q

what occurs if segmental spinal limb reflexes are affected

A

lower motor neuron lesion

36
Q

what is hyper-reflexia

A

real –> release of inhibition from UMNs

pseudo –> reduction in action of antagonistic pair

37
Q

what is clonus

A

oscilation of stifle

UMN lesion affecting pelvic limb

38
Q

what is exaggerated patellar reflex

A

unopposed reflex

LMN sciatic dysfunction

disproportionately large and uncontrolled stifle extension

due to failure of antagonistic pair

Module 8 (43 decks)

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