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Neuroscience > Spinal Reflexes > Flashcards

Spinal Reflexes Flashcards

1
Q

The brachial plexus supplies

A

the thoracic limb

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2
Q

Which nerves arise from the brachial plexus

A

musculocutaneous, axillary, median, ulnar and radial

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3
Q

Which nerve innervates the most lateral digit (thoracic limb)

A

Ulnar nerve

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4
Q

What does the radial nerve innervate

A

All digits and dorsal aspect of paw

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5
Q

What nerves form the brachial plexus

A

C6 - T2

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6
Q

What nerves form the lumbosacral plexus

A

L4 - S3

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7
Q

What does the lumbosacral plexus supply

A

Pelvis limb

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8
Q

What nerve supplies the lateral most digit of the pelvic limb

A

Sciatic nerve (from L6-S1)

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9
Q

What nerve supplies the medial digit of the pelvic limb

A

Saphenous branch of the femoral nerve

Arises from L4-L6

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10
Q

What does the peroneal (L6-S1) nerve supply

A

Dorsal aspect of the paw of pelvic limb

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11
Q

What is the cutaneous trunci muscle responsible for

A

Twitching of skin, shivering

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12
Q

What type of pathway is occurring in the cutaneous trunci reflex

A

Sensory (GSA)

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13
Q

What occurs in cutaneous trunci reflex

A
  • Stimulation of cutaneous sensory nerves along back
  • Impulse generated by sensory nerve
  • Enters spinal cord seg about 1-2 vertical segments cranial to point of stimulation
  • Impulse transmitted via spinal pathways of ascending fasiculus proprius
  • Goes through thoracolumbar spinal cord to level of C8-T1
  • Forms synapse on lower motor neurons of lateral thoracic nerve
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14
Q

What does stimulation of cutaneous trunci result in

A

Bilateral response

- contraction of cutaneous trunci on both sides, greater response on stimulated side

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15
Q

How do you proceed with cutaneous trunci reflex test

A

Start from caudal lumbar region and proceed cranially one or two vertebrae at a time

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16
Q

What is the clinical significance of cutaneous trunci reflex

A

Location of C8 and T1 spinal cord lesion and brachial plexus injuries
- evaluating animals with transverse thoracolumbar spinal cord injury

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17
Q

What does the stretch or myotatic reflex do

A

Assesses maintenance and control of muscle tone

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18
Q

What muscles have myotatic reflex

A

All skeletal except extraocular eye muscles

19
Q

What is the stimulus in myotatic reflex

A

Stretching of muscle which activated neuromuscular muscle spindle (stretch receptors)
- alpha motor neuron

20
Q

What is the response of myotatic reflex

A

Contraction of the same muscle

21
Q

What pathway is used in myotatic reflex

A

Sensory (GSA)

22
Q

Where is the integrating center for the spinal nerves located

A

In the same spinal cord segment

23
Q

Where is the integrating center for cranial nerves

A

In the brain stem

24
Q

What is an example of a myotatic reflex

A

Patellar reflex

25
Q

Is the patellar reflex monosynaptic, disynaptic or multisynaptic

A

Monosynaptic Reflex Arc

- so there is just one synapse, no interneurons

26
Q

What is the stimulus in patellar reflex

A

Dog positioned in lateral recumbency
Evoke by tapping patellar tendon below patella with neural hammer or pleximeter
Stretches quadriceps tendon –> stimulates muscle spindles
This triggers afferent impulse in sensory nerve fiber of femoral nerve that ascends to L4-L6

27
Q

What is the response to patellar reflex

A

Sensory nerve synapses with motor neuron

-conducting efferent impulse to quadriceps triggers contraction and causes leg to kick by extending stifle

28
Q

What is the clinical significance of an absence or decrease in patellar reflex

A

Lesion/disease of femoral nerve

Lesion/disease of L4, L5 and L6 spinal cord segments

29
Q

What is the clinical significance of an exaggerated patellar reflex

A

Upper motor neuron spinal cord lesion

30
Q

What is the withdrawal/flexion reflex

A

Involuntary contraction of muscles in response to noxious stimulus
ie. pinching

31
Q

What is the withdrawal/flexion reflex used to assess

A

Spinal cord at C6-T2 in thoracic limb

Spinal cord at L6-S2 in pelvic limb

32
Q

What is the stimulus in withdrawal/flexion reflex

A

Noxious stimuli on skin of limb –> compression or pinching of toes
Test for nociceptive pathway (mediated by pain receptors)

33
Q

What is the response to the withdrawal/flexion reflex

A

Flexion of all joints of limb, protective response

Specific sensory nerves are assessed based on area of skin stimulated

34
Q

What occurs in the thoracic limb in a normal withdrawal/flexion reflex

A

Flexion of shoulder, elbow and carpus

35
Q

What occurs in pelvic limb in normal withdrawal/flexion reflex

A

Flexion of hip, stifle and hock

36
Q

Why should you evaluate both lateral and medial digits in a withdrawal/flexion reflex

A

Because lateral and medial have different innervations

37
Q

What is the cross extensor reflex

A

Abnormal reflex found in recumbent animals when doing withdrawal/flexion reflex

38
Q

What occurs in the cross extensor reflex

A

Extension of the contralateral limb

Increased tone in extensors of opposite limb to maintain posture in standing animals

39
Q

Why is the cross extensor reflex a bad prognosis

A

It indicates reduced input from higher centers (upper motor neuron disease) because integration in producing the proper extension on collateral limb is complex and involves brainstem and cerebral cortex

40
Q

What nerve is associated with the anal/perineal reflex

A

Pudendal nerve (S1-S3)

41
Q

What does the pudendal nerve supply

A
  • external sphincter of anus
  • striated muscles of penis, vulva and vestibule
  • urethralis muscle
  • skin of perineum and caudal thigh
42
Q

What is the stimulus in an anal/perineal reflex

A

compression of skin of anus or perineum using forceps

43
Q

What is the response in an anal/perineal reflex

A

Evokes an immediate contraction of anal sphincter and flexion of the tail –> so long as caudal spinal cord segment and nerve are intact

44
Q

What is clonus

A

Joint moves repeatedly after a single stimulus

Neuroscience (10 decks)

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