L46 Spinal Reflexes

Question 1

Define reflexes

Answer 1

predictable stereotyped response to a specific stimulus (specific muscular rnxs to stretch)

Question 2

Define monosynaptic reflex

Answer 2

afferent and efferent limbs are directly connected (deep tendon reflex)

one single synapse

Question 3

Define polysynaptic reflex

Answer 3

afferent and efferent limb are interconnected with one or more interneurons (pupillary light reflex, cutaneous reflex)

Question 4

what are the components of the reflex arc?

Answer 4

sensory receptor (muscle spindle, golgi tendon organ)
afferent neuron
synapse on efferent neuron (LMN)
NMJ
muscle

Question 5

what are examples of reflexes

Answer 5

• deep tendon (myotactic) reflex
• golgi tendon (inverse myotactic) reflex
• flexion crossed extension reflex

Question 6

what is the afferent limbs?

Answer 6

muscle spindle and Ia fibers
golgi tendon organ and Ib fibers
free nerve endings and Adelta fibers

Question 7

what make up efferent limbs?

Answer 7

alpha motor neuron
homonymous muscle
synergist muscle
antagonist muscle

Question 8

what is the nature and purpose of the deep tendon reflex?

Answer 8

when a muscle is passively stretched, it reflexively contracts
the reflex dictates muscle tone under regulation by UMN

Question 9

what segments are involved in inspiration using the diaphragm

Answer 9

C3,4,5

Question 10

what segments are involved in shoulder abduction using the deltoid?

Answer 10

C5

Question 11

what segments are involved in elbow flexion involving the biceps brachi and brachialis

Answer 11

C5,6

Question 12

what segments are involved in wrist extension using ECRL and ECRB

Answer 12

C6,7

Question 13

what segments are involved in elbow extension using triceps?

Answer 13

C7,8

Question 14

what segments are involved in finger flexion using FDS and FDP

Answer 14

C8

Question 15

what segments are involved in finger abduction and adduction using interossei

Answer 15

C8, T1

Question 16

what segments are involved in thigh adduction using AL and AB

Answer 16

L2,3,4

Question 17

what segments are involved in knee extension using quads

Answer 17

L3,4

Question 18

what segments are involved in great toe extension using EHL

Answer 18

L5, S1

Question 19

what segments are involved in ankle plantar flexion using gastroc and soleus

Answer 19

S1,2

Question 20

what segments are involved in anal contraction using sphincter ani externus

Answer 20

S2,3,4

Question 21

what is the landmark for the ankle jerk reflex

Answer 21

S1

Question 22

what is the landmark for the knee jerk reflex

Answer 22

L2,3,4

Question 23

what is the landmark for the biceps and brachioradialis reflex

Answer 23

C5,6

Question 24

what is the landmark for the triceps reflex

Answer 24

C7

Question 25

describe the scale for reflex testing

Answer 25

``` pretty subjective... 0 no response 1+ low normal 2+ average normal 3+ high normal 4+ hyperactive with clonus ``` * normal responses vary widely within a range * differences between sides = DISEASE!

Question 26

define clonus

Answer 26

a series of involuntary, rhythmic, muscular contractions and relaxations. They are not like fasciculations because they are not small twitches, they are large motions usually initiated by a reflex

Question 27

the stretch (myotactic) reflex works as a _____ to maintain muscle length at a desires value

Answer 27

negative feedback loop

Question 28

what is the function of the gamma motor neurons in the myotactic reflex?

Answer 28

Are responsible for contracting the ends of the muscle spindle to keep its length identical to the muscle fibers in an effort to maintain monitoring of the muscle length at all times

Question 29

why are inverse myotactic reflexes slower than myotactic reflexes?

Answer 29

because Ib fibers are small diameter and because the inverse myotactic reflex is polysynaptic and myotactic reflex is monosynaptic

Question 30

what is the function of the inverse myotactic reflex?

Answer 30

protect muscle and tendon when stimulated constantly | maintain posture

Question 31

Describe the flexion reflex or the "withdrawal reflex"

Answer 31

In response to painful (nociceptive) stimuli, causing ipsilateral rapid flexion a protective mechanism ipsilateal extensor responses are suppressed ``` Pain afferents (A-delta and C-fibers) will stimulate excitatory interneurons (present at each spinal segment) that synapse on alpha motor neurons to flex the necessary muscle ```

Question 32

describe the flexor crossed extensor reflex

Answer 32

The Flexion Reflex is often associated with this Flexion Crossed Extension Reflex in the contralateral limb This will support the contralateral leg to maintain balance if the flexion reflex causes the ipsilateral leg to lift when you step on a pin c. SUMMARY i. Ipsilateral flexor stimulation and extensor inhibition ii. Contralateral flexor inhibition and extensor stimulation

Question 33

Summary of the flexor crossed extensor reflex - ipsilateral flexor _____ and extensor ____ - contralateral flexor _____and extensor ___

Answer 33

stimulation, inhibition | inhibition, stimulation

Question 34

what type of reflex is the plantar reflex?

Answer 34

polysynaptic

Question 35

what does a normal adult plantar reflex look like?

Answer 35

toes all flex

Question 36

what does an abnormal plantar reflex look like?

Answer 36

toes fan out and big toe extends

Question 37

why do newborns to 1 yo have +babinski sign or abormal plantar reflex (toes are fanning)? (non-pathological positive plantar reflex)

Answer 37

because their pyramidal (corticospinal) tract is immature and not completely myelinated yet

Question 38

what does a positive babinski sign in adults indicate?

Answer 38

cortical, axonal disruptions, demyelination etc.

Question 39

what are causes of hyporeflexia (diminished or absent reflexes)?

Answer 39

- lesion of spinal cord segment - leison of the efferent limb (LMN lesion) - disease of the NMJ - lesion of the muscle - peripheral n. lesion - lesion of afferent limb (sensory loss)

Question 40

what does hyperreflexia suggest?

Answer 40

UMN lesion clonus confirms it

Question 41

where can UMN damage be located?

Answer 41

in motor center (precentral gyrus etc.) or somewhere along motor tracts

Question 42

what does hyperreflexia usually follow

Answer 42

spinal shock in spinal cord transections!

Question 43

describe spinal shock

Answer 43

acute transection of the spinal cord leads to this during this period (right after accident), spinal reflexes below the lesion are suppressed and it may take several weeks until spinal reflexes truetn poorly understood