Neurophysiology - Jaw reflexes

Question 1

What is the definition of a reflex?

Answer 1

a predictable response to a given stimulus

Question 2

Name the parts of the reflex arc

Answer 2

Question 3

what is reflex latency?

Answer 3

time from stimulus to effect

Question 4

Why is there a latency in reflex?

Answer 4

there is a conduction time of the afferent neurons

Synaptic delay

conduction time of efferent neurones

Question 5

What is the conduction time of a small diameter afferent neurone?

Answer 5

smaller conduction time, smaller AP

Question 6

What is the minimum synaptic delay per synapse?

Answer 6

0.2 ms per synapse

Question 8

What are integrated actions?

Answer 8

walking, breathing, parts of swallowing

Question 9

What are the 2 categories of jaw reflexes?

Answer 9

vertical

horizontal

Question 10

What is the movement of a vertical jaw reflex?

Answer 10

move mandible relative to maxilla in vertical plane

jaw jerk
jaw opening
jaw unloading

Question 11

What is the movement of a horizontal jaw reflex?

Answer 11

move mandible relative to maxilla in protrusive retrusive or lateral direction

Question 12

What are the 3 vertical jaw reflexes?

Answer 12

jaw jerk
jaw opening
jaw unloading

Question 13

What type of reflex is the jaw jerk reflex?

Answer 13

a phasic stretch reflex

Question 14

What is the stuimulus odf the jaw jerk reflex?

Answer 14

sudden jaw opening

Question 15

What is the response of the jaw jerk reflex?

Answer 15

activation of jaw closing muscles

Question 16

How many synapses are involved in the jaw jerk reflex?

Answer 16

1

monosynaptic

Question 17

What is the synapse for the jaw jerk reflex between?

Answer 17

jaw closing muscles spindles and jaw closing motor neurons

Question 18

What is the latency in the jaw jerk reflex?

Answer 18

8ms

Question 19

What are the stages in the jaw jerk reflex?

Answer 19

1. stimulus: stretch (via chin tap)
2. receptor: muscle spindle
3. synapse(s): 1 in V motor nucleus
4. effect: contraction of masseter muscle

latency: 8ms

Question 20

Answer 20

1. trigeminal mesencephalic nucleus
2. trigeminal motor nucleus

Question 21

How do you record AP from muscles?

Answer 21

electromyography

Question 22

What is the role of the jaw jerk reflex in the phasic situation?

Answer 22

plays a role in load compensation during chewing –> e.g. biting something hard and you need more force, muscle spindles are stretched and the force of the bite is stronger

stabilization during vigorous head movements - e.g. during running

Question 23

What is the role of jaw jerk reflex in the tonic situation?

Answer 23

resist gravity

help maintain posture? … e.g. rest position of the mandible

Question 24

What is the rest position of the mandible?

Answer 24

teeth apart at rest

Question 25

How is the rest/postural position of the mandible maintained?

Answer 25

minimal muscle activity or governed by muscle elasticity

active (stretch reflex) or passive (tissue elasticty)