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Module 8 > Spinal Reflexes SDL > Flashcards

Spinal Reflexes SDL Flashcards

1
Q

what are the components of the reflex arc

A
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2
Q

what are touch/nocioception

A
  1. free nerve endings: mainly in hairy skin (not specific to a particular stimulus)
  2. terminal encapsulations: hairy skin –> pacinian (local pressure), ruffini (tension in collagen fibres), merkels (deformation of skin), meissners (sideways shearing)
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3
Q

what are the components of muscle spindle receptors

A
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4
Q

what is the muscle spindle and stretch reflex (8)

A
  1. spindle organs are located within skeletal muscle belly
  2. composed of intrafusal fibres (gamma efferent neuron and alpha efferent neuron)
  3. stimulation of Ia afferent fibre occurs when tension occurs in nuclear region of the intrafusal muscle fibre
  4. impuse created by tension travels in the la afferent fibre, with its cell body in spinal ganglion
  5. the axon synapses on the alpha efferent neuron within the ventral grey horn of the spinal cord
  6. results in contraction of the extrafusal muscle fibre
  7. concurrently collaterals from the Ia afferent stimulate interneurons in the ventral grey horn that are inhibitory to the alpha neurons innervating antagonistic muscles
  8. results in constant, low level of contraction within muscles –> results in muscle tone, as well as ability to maintain posture in gravitational forces
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5
Q

what are the structures shown

A
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6
Q

what are the structures shown

A
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7
Q

what are the structures shown

A
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8
Q

what are the structures shown

A
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9
Q

what occurs when the reflex arc is interrupted

A

receptor - diminished/absent

afferent nerve - diminished/absent

efferent nerve - diminished/absent

effector - diminished/absent

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10
Q

how are afferent/efferent sides of the reflex arc differentiated

A
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11
Q

what is the afferent pathway of the withdrawal reflex touch/nocioception

A
  1. afferent pathway: pinching digit –> stimulation of sensory receptors in skin and deep subcutaneous tissues

dorsal aspect of paw: sensory input travels up radial nerve

palmar aspect: sensory input travels up ulnar/median nerves

  1. travels to nerve cell body (in spinal ganglion) and axon passes into spinal cord through dorsal roots
  2. spinal cord segments: radial nerve (C7, C8, T1 (T2)), ulnar nerve (C8, T1 (T2)), median nerve (C8, T1 (T2))
  3. axons extend cranial/caudal in dorsolateral funiculus with collaterals synapsing on interneurons within grey matter of spinal cord
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12
Q

what is the efferent pathway of the withdrawal reflex touch/nocioception

A
  1. interneurons synapse on motor neurons in ventral grey matter

2. shoulder flexion: axillary (C6-8) and radial (C7-T2) nerves

3. elbow flexion: musculocutaneous (C6-8) nerves

4. carpal/digital flexion: median (C8-T2) and ulnar (C8-T2) nerves

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13
Q

what is the afferent pathway of the patellar reflex

A
  1. as tendon is stretched –> stimulation of nuclear bag region of annulospiral organ of the intrafusal muscle fiber
  2. receptor’s impulse travels in the 1A afferent nerve fibers
  3. sensory fibers travel in the femoral nerve to the cell body in the spinal root ganglion
  4. axon enters the spinal cord via the dorsal nerve root L4-5(6)
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14
Q

what is the efferent pathway of the patellar reflex

A
  1. axon travels into ventral grey matter and stimulates alpha motor neuron
  2. axons of these neurons travel in the femoral nerve and cause contraction of quadriceps and extension of stifle
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15
Q

what are upper motor neurons

A

never leaves CNS

cell body in brainstem or forebrain

axons synapse on LMN in spinal cord

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16
Q

what are the functions of upper motor neuron

A
  1. initiate voluntary movement (organizes & directs activity of the LMN)
  2. maintaining muscle tone to retain balance and control posture (modulates LMN activity on antigravity muscles)
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17
Q

what are lower motor neurons

A

connects CNS with muscle

cell body in spinal cord

axons project into peripheral nervous system (PNS) via spinal nerves to connect with striated or smooth muscles at neuromuscular junction

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18
Q

what are the functions of the LMN

A

induce muscle contraction when stimualted

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19
Q

how is LMN activity modulated

A

predominatly inhibitory action of the UMN

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20
Q

what does damage of UMN cause

A

release of LMN from inhibition = increased extensory tone, increased reflexes and spasticity

21
Q

what criteria is needed for differentiation between LMN and UMN signs

A
  1. posture
  2. motor function
  3. spinal reflexes
  4. resting muscle tone
  5. muscle atrophy
22
Q

how does posture allow differentiation between LMN and UMN

A

LMN: difficulty in supporting weight

UMN: normal

23
Q

how does motor function allow differentiation between LMN and UMN

A

LMN: flaccid paresis/paralysis

UMN: spastic paresis/paralysis

24
Q

how does resting muscle tone allow differentiation between LMN and UMN

A

LMN: decreased to absent

UMN: normal to increased

25
Q

how does spinal reflexes allow differentiation between LMN and UMN

A

LMN: decreased to absent

UMN: normal to increased

26
Q

how does muscle atrophy allow differentiation between LMN and UMN

A

LMN: early & severe (neurogenic atrophy)

UMN: late & mild (disuse atrophy)

27
Q

what are the neurolocalizations based on the presence of UMN or LMN signs

A
28
Q

what lesions will induce LMN signs to all limbs

A

affecting spinal nerve roots or peripheral nerves (polyradiculopathies or polyneuropathies)

29
Q

what is the peripheral nerve organization

A

cranial intumescence: brachial plexus and thoracic limb

caudal intumescence: lumbosacral plexus and pelvic limb, sphincters and tail

30
Q

what are the reflexes associated with cervical intumescence

A
  1. flexor (withdrawal) reflex: sensory –> varies with area stimulated

motor–> musculocutaneous, axillary, median, ulnar, radial

  1. cutaneous trunci reflex: sensory –> skin dorsal trunk (T2-L4)

motor –> lateral thoracic nerve

31
Q

how is the thoracic limb withdrawal reflex tested

A

lateral recumbency

pinch digit with fingers to stimulate nociceptors

varying degree of stimulus

32
Q

what is the reflex of thoracic limb withdrawal

A

flexion of carpus, elbow and shoulder

33
Q

what is the anatomy in the thoracic limb withdrawal

A
  1. afferent: radial, median, ulnar nerves (C7, C8, T1 & T2 segments)
  2. efferent: axiallary, musculocutaneous, median, ulnar, radial nerves (C6, C7, C8, T1, T2 segments)
34
Q

how is the cutaneous trunci reflex performed

A

pinch skin over dorsum

1 inch off midline from level of iliac wing to T2 vertebra (shoulder) on both sides

35
Q

what is the reflex of the cutaneous trunci

A

bilateral contraction of the cutaneous trunci muscle, whichever side stimulated

36
Q

what is the anatomy of the cutaneous trunci pathways

A
  1. afferent: spinal nerves T2-L2 segments
  2. efferent: C8-T1 spinal cord segments, lateral thoracic nerve
37
Q

how is cutaneous trunci reflex localized

A
38
Q

what are the test reflexes associated with lumbosacral intumescence

A
  1. flexor (withdrawal) reflex: sensory and motor –> sciatic nerve
  2. patellar reflex: sensory and motor –> femoral
  3. perineal reflex –> sensory and motor –> pudendal
39
Q

how is the spinal patellar reflex performed

A

hold patients limb such that the stifle is semi-flexed

percussion of patellar tendon (muscle stretch receptors)

40
Q

what is the patellar reflex

A

brisk, controlled extension of stifle

41
Q

what is the anatomy of the patellar reflex

A

afferent and efferent pathways:

femoral nerve

spinal cord segments L4-L6 (cranial aspect lumbar intumescence)

42
Q

how is the pelvic limb withdrawal test done

A

lateral recumbency

pinch digit with fingers (stimulate nociceptors)

varying degree of stimulus

43
Q

what is the pelvic limb withdrawal reflex

A

flexion of hip, stifle and tarsus

44
Q

what is the anatomy of the pelvic limb withdrawal

A

afferent and efferent pathways:

sciatic nerve

L6, L7 and S1 spinal cord segments

45
Q

how is the perineal reflex done

A

pinch perineum (hemostat)

both sides

nociceptors/touch receptors perineum

46
Q

what is the perineal reflex

A

contraction of the anus and clamping of tail

pudendal nerves (anus)

caudal nerves (tail)

47
Q

what is the pathway of the perineal reflex

A

pudendal nerve

S1 and Cd5 spinal cord segments

48
Q

how can spinal reflexes be graded

A

absent (0)

decreased (1)

normal (2)

increased (3)

clonus (4): repetitive/oscillating reflex following one single stimulation

Module 8 (43 decks)

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