Spinal Reflexes

Question 1

The brachial plexus supplies

Answer 1

the thoracic limb

Question 2

Which nerves arise from the brachial plexus

Answer 2

musculocutaneous, axillary, median, ulnar and radial

Question 3

Which nerve innervates the most lateral digit (thoracic limb)

Answer 3

Ulnar nerve

Question 4

What does the radial nerve innervate

Answer 4

All digits and dorsal aspect of paw

Question 5

What nerves form the brachial plexus

Answer 5

C6 - T2

Question 6

What nerves form the lumbosacral plexus

Answer 6

L4 - S3

Question 7

What does the lumbosacral plexus supply

Answer 7

Pelvis limb

Question 8

What nerve supplies the lateral most digit of the pelvic limb

Answer 8

Sciatic nerve (from L6-S1)

Question 9

What nerve supplies the medial digit of the pelvic limb

Answer 9

Saphenous branch of the femoral nerve

Arises from L4-L6

Question 10

What does the peroneal (L6-S1) nerve supply

Answer 10

Dorsal aspect of the paw of pelvic limb

Question 11

What is the cutaneous trunci muscle responsible for

Answer 11

Twitching of skin, shivering

Question 12

What type of pathway is occurring in the cutaneous trunci reflex

Answer 12

Sensory (GSA)

Question 13

What occurs in cutaneous trunci reflex

Answer 13

• 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

Question 14

What does stimulation of cutaneous trunci result in

Answer 14

Bilateral response

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

Question 15

How do you proceed with cutaneous trunci reflex test

Answer 15

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

Question 16

What is the clinical significance of cutaneous trunci reflex

Answer 16

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

Question 17

What does the stretch or myotatic reflex do

Answer 17

Assesses maintenance and control of muscle tone

Question 18

What muscles have myotatic reflex

Answer 18

All skeletal except extraocular eye muscles

Question 19

What is the stimulus in myotatic reflex

Answer 19

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

Question 20

What is the response of myotatic reflex

Answer 20

Contraction of the same muscle

Question 21

What pathway is used in myotatic reflex

Answer 21

Sensory (GSA)

Question 22

Where is the integrating center for the spinal nerves located

Answer 22

In the same spinal cord segment

Question 23

Where is the integrating center for cranial nerves

Answer 23

In the brain stem

Question 24

What is an example of a myotatic reflex

Answer 24

Patellar reflex

Question 25

Is the patellar reflex monosynaptic, disynaptic or multisynaptic

Answer 25

Monosynaptic Reflex Arc | - so there is just one synapse, no interneurons

Question 26

What is the stimulus in patellar reflex

Answer 26

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

Question 27

What is the response to patellar reflex

Answer 27

Sensory nerve synapses with motor neuron | -conducting efferent impulse to quadriceps triggers contraction and causes leg to kick by extending stifle

Question 28

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

Answer 28

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

Question 29

What is the clinical significance of an exaggerated patellar reflex

Answer 29

Upper motor neuron spinal cord lesion

Question 30

What is the withdrawal/flexion reflex

Answer 30

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

Question 31

What is the withdrawal/flexion reflex used to assess

Answer 31

Spinal cord at C6-T2 in thoracic limb | Spinal cord at L6-S2 in pelvic limb

Question 32

What is the stimulus in withdrawal/flexion reflex

Answer 32

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

Question 33

What is the response to the withdrawal/flexion reflex

Answer 33

Flexion of all joints of limb, protective response | Specific sensory nerves are assessed based on area of skin stimulated

Question 34

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

Answer 34

Flexion of shoulder, elbow and carpus

Question 35

What occurs in pelvic limb in normal withdrawal/flexion reflex

Answer 35

Flexion of hip, stifle and hock

Question 36

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

Answer 36

Because lateral and medial have different innervations

Question 37

What is the cross extensor reflex

Answer 37

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

Question 38

What occurs in the cross extensor reflex

Answer 38

Extension of the contralateral limb | Increased tone in extensors of opposite limb to maintain posture in standing animals

Question 39

Why is the cross extensor reflex a bad prognosis

Answer 39

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

Question 40

What nerve is associated with the anal/perineal reflex

Answer 40

Pudendal nerve (S1-S3)

Question 41

What does the pudendal nerve supply

Answer 41

- external sphincter of anus - striated muscles of penis, vulva and vestibule - urethralis muscle - skin of perineum and caudal thigh

Question 42

What is the stimulus in an anal/perineal reflex

Answer 42

compression of skin of anus or perineum using forceps

Question 43

What is the response in an anal/perineal reflex

Answer 43

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

Question 44

What is clonus

Answer 44

Joint moves repeatedly after a single stimulus