Reflexes- Definitions

Question 1

Monosynaptic/Deep Tendon/Myotactic Reflex

Answer 1

afferent and efferent limbs are directly connected (one single synapse)

Question 2

Polysynaptic Reflex

Answer 2

Afferent and Efferent limbs are connected by one or more interneuron

Question 3

Reflex Arc Syndrome

Answer 3

Sensory receptor (Spindle/golgi tendon)
Afferent Neuron
Synapse on efferent (LMN neuron)
Muscle Contraction

Question 4

Types of Stretch Reflexes

Answer 4

Deep Tendon Reflex
Golgi Tendon Reflex (inverse myotactic)
Flexion Crossed Extension Reflex

Question 5

Afferent Limbs

Answer 5

Spindle –> 1a

Golgi Tendon –> 1b fibers

Question 6

Efferent Limbs

Answer 6

A-gamma –> Intrafusal fibers

A-Alpha –> extrafusal fibers

Question 7

Basic Reflex Arc

Answer 7

Is in response to passive muscle stretching

Question 8

what fibers directly stimulate alpha motor fibers to contract the stretched muscle?

Answer 8

1a- Fibers (spindle)

Question 9

1a fibers also stimulate inhibitory interneurons that eventually inhibit what neurons on the antagonist muscle?

Answer 9

alpha motor neurons

Question 10

What are gamma motor neurons responsible for?

Answer 10

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 11

what is the location and function of the golgi tendon?

Answer 11

located in series between the tendon and extrafusal fibers which are sensitive to tension

Question 12

what fiber innervates the golgi tendon?

Answer 12

single 1b axon which is large, myelinated and with high velocity

Question 13

what happens to the 1b fiber once it enters the tendon organ?

Answer 13

loses its myelination once it enters the tendon organ and intertwines the collagen chains

Question 14

does contraction of the muscle increase or decrease 1b-axon firing?

Answer 14

Increase

Question 15

what physiological response does increasing 1b axon firing have?

Answer 15

increase inhibition on the alpha motor neuron

Question 16

what does having inhibition on the alpha motor neuron do?

Answer 16

ensures even distribution of tension and contraction as well as avoiding excessive contraction to the point of damage (known as the inverse myotactic reflex)

Question 17

What is the primary function of the golgi tendon?

Answer 17

protection (increased tension will increase inhibition on contraction to avoid excessive contraction that can lead to damage)
posture ( via the patellar tendon and the quadriceps muscle)

Question 18

what is the flexion or withdraw reflex?

Answer 18

in response to painful stimuli, causing rapid flexion as a protective mechanism 
pain afferents (a delta and c fibers) will stimulate excitatory interneurons that synapse on alpha motor neurons to flex the necessary muscle.

Question 19

what is the flexion crossed extension reflex?

Answer 19

Flexion reflex is associated with the 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 pain.
so you inhibit the ipsilateral flexor stimulation and stimulate the contralateral flexor

Question 20

what is the Babinski sign?

Answer 20

dorsiflexion of the big toe, often associated by fanning of the other toes.

Question 21

why is a positive babinski sign in a newborn normal?

Answer 21

newborns have immature corticospinal tract

Question 22

What does a positive babinski sign indicate?

Answer 22

UMN damage to spinal cord or brain disease to the corticospinal tract

Question 23

If a patient exhibits hyperflexia what type of lesion is this associated with?

Answer 23

UMN lesion in the cortex or somewhere in the corticospinal tract (remember after spinal shock)

Question 24

what is spinal shock?

Answer 24

acute damage to the spinal cord causing immediate areflexia caudal to injury; reflexes return in weeks

Question 25

what is the lesion associated with hyporeflexia?

Answer 25

LMN reflex, NMJ muscle disease, sensory loss or peripheral nerve lesion

Question 26

what is an example of the flexion reflex or “withdrawal reflex”?

Answer 26

pulling the hand away from a hot surface