Muscle Spindle Outcomes

Question 1

What is the myotatic reflex?

Answer 1

When a muscle is pulled, it pulls back

Question 2

What innervates the intrafusal muscle fibres?

Answer 2

• sensory afferents

- gamma motor neurone efferents

Question 3

Supinator reflex

Answer 3

C5-C6

Question 4

Biceps reflex

Answer 4

C5-C6

Question 5

Triceps reflex

Answer 5

C7

Question 6

Quadriceps reflex (knee)

Answer 6

L3-L4

Question 7

Gastrocnemius reflex? (ankle)

Answer 7

S1

Question 8

What innervates the non-contractile region of intrafusal fibres?

Answer 8

Ia afferents

Question 9

What innervates the contractil region of intrafusal fibres?

Answer 9

Gamma motor neurones

Question 10

What causes the spindle to contract?

Answer 10

Stimulation of the gamma fibres

Question 11

What are Nuclear bag 1 (dynamic) fibres sensitive to?

Answer 11

Rate of change of muscle length

innervated by dynamic gamma neurones

Question 12

What are nuclear bag 2 (static) fibres sensitive to?

Answer 12

Absolute length of muscle

innervated by static gamma neurones

Question 13

What are chain fibres sensitive to?

Answer 13

The absolute length of the muscle

innervated by gamma neurones

Question 14

Where are golgi tendon organs located?

Answer 14

At the junction between the muscle and tendon

Question 15

What do golgi tendon organs monitor?

Answer 15

The changes in muscle tension

Question 16

What innervates golgi tendon organs?

Answer 16

Ib fibres

Question 17

What do golgi tendon organs do?

Answer 17

Regulate muscle tension (i.e. protect muscle from overload and make sure that muscle tension is in optimal range)

Question 18

What do proprioceptive axons do?

Answer 18

Respond to changes in angle, direction and velocity of movement of a joint. Also prevent excessive flexion, or extension

Question 19

Function of free nerve endings?

Answer 19

Nociceptive role

Question 20

Function of golgi endings

Answer 20

Protective role

Question 21

Function of paciniform endings

Answer 21

Acceleration detectors

Question 22

Function of ruffini endings

Answer 22

Sense static position and speed of movments

Question 23

What do spinal interneurones do?

Answer 23

Integrate incoming information ro generate an output

• they mediate the inverse myotatic reflex
• reciprocal inhibition between extensors and flexors

Question 24

Give an example of reciprocal inhibition

Answer 24

Myotatic reflex causes the homonymous extensor muscle (quadriceps) to contract, but for the leg to extend the antagonist flexor muscle (hamstring) must simultaneously relax

Question 25

What is the flexor reflex?

Answer 25

Noxious stimulus causes limb to flex by:
contraction of flexor muscles via excitatory interneurones
relaxation of extensor muscles via excitatory and inhibitory interneurones

Question 26

What is the crossed extensor reflex?

Answer 26

Noxious stimulus causes limb to extend by:
contraction of extensor muscles via excitatory interneurones
relaxation of flexor muscles via excitatory and inhibitory interneurones

This reflex enhances postural support during withdrawal of a foot from a painful stimulus (you do not fall over!)