N19- Trigeminal proprioception

Question 1

what is proprioception?

Answer 1

Awareness of position of body parts in relation to each other and surroundings

Question 2

what is kinaesthesia?

Answer 2

movement awareness

Question 3

what receptors are involved in proprioceptors?

Answer 3

• muscle spindles
• golgi tendon organs
• joint receptors

Question 4

Describe the extrafusal fibres.

Answer 4

• bulk of the muscle fibres

- contractile

Question 5

Describe the intrafusal fibres.

Answer 5

• muscle spindles
• specialised muscle fibres
• within a ct capsule

Question 6

how do muscle spindles lie in comparison to muscle fibres?

Answer 6

lie parallel to each other

Question 7

how do the muscle itself and muscle spindles contract?

Answer 7

contract independent of one another as they have a different nerve supply

Question 8

Describe the structure of the muscle spindle.

Answer 8

Both ends of the spindle are contractile and there is a non-contractile central portion which can be stretched

Question 9

How are the afferents activated in muscle spindles?

Answer 9

activated by stretch

Question 10

what does the primary annulo-spiral nerve ending detect?

Answer 10

Detects length of fibres and speed of change of length

Question 11

what does the secondary (flower-spray) nerve endings detect?

Answer 11

detect length of fibres

Question 12

what is the efferent neurone of the muscle spindles?

Answer 12

Gamma motor neurone

Question 13

what are the extrafusal fibres supplied by?

Answer 13

alpha motor neurons

Question 14

what is the muscle spindle role?

Answer 14

• Information about muscle length
• act to maintain muscle length
• load compensation

Question 15

what happens when muscle spindle is stretched during reflexes?

Answer 15

muscle spindle contracts to maintain original position

Question 16

Describe the spindles in action with the water bucket scenario .

Answer 16

• Bucket fills with water
• Biceps spindles stretch
• Increased motor neurone drive to biceps
• Muscle length maintained

Question 17

where are muscle spindle cell bodies found?

Answer 17

trigeminal mesencephalic nucleus

Question 18

where do muscle spindle afferents synapse?

Answer 18

• V motor nucleus

- Other areas linked to sensorimotor regulation: cerebellum and cerebral cortex

Question 19

what happens when the muscle shortens?

Answer 19

• Contract muscle spindles using gamma motor fibres

- drives the length of extrafusal muscle during contractions

Question 20

what are the roles of gamma motor neurones?

Answer 20

• Cause contraction of intrafusal fibres
• Maintain tension in spindle
•  Maintain spindle afferent activity
•  α‐γ co‐activation

Question 21

During load compensation, what happens during α‐γ co‐activation?

Answer 21

• muscle shortens -jaw closes
• spindle tension maintained
• spindle activity maintained
• (muscle is not changing length, just force increasing)

Question 22

During load compensation, what overcomes the resistance of the carrot?

Answer 22

• muscle doesn’t shorten
• γ-activity stretches spindle
• spindle activity increased
• α drive to muscle increases

Question 23

what prevents teeth crashing together during load compensation?

Answer 23

The length of intrasfusal fibres causes activation of jaw opening muscles

Question 24

where are more spindle fibres found in skeletal muscle?

Answer 24

in places for more fine motor control, detailed movements i.e the hand

Question 25

where are Golgi tendon organs found?

Answer 25

in tendons in series with muscle fibres

Question 26

where are very few, if any, Golgi tendons organs?

Answer 26

masticatory muscles

Question 27

what type of receptors are golgi tendon organs ?

Answer 27

tension receptors

Question 28

what role does Golgi tendon organs have?

Answer 28

Role in (inhibitory) reflex ‐prevention of XS stretch of muscle

Question 29

what does Golgi tendon do in response to muscle moving against great resistance?

Answer 29

starts firing to offer feedback to muscle system which controls the amount of force you can generate from that muscle to prevent muscle damage

Question 30

what plays the equivalent role to Golgi tendon in the mouth?

Answer 30

receptors in periodontal ligament provide the same feedback in the mouth

Question 31

where are the 3 joint receptors , where are they found and what is their role?

Answer 31

-Pacinian – in ligaments ‐ acceleration - Golgi – in ligament ‐ position - Ruffini ‐ in capsule‐ movement

Question 32

Name a test of proprioceptive ability?

Answer 32

- interdental detection - can detect 50micrometers between teeth - ability to reposition the jaw -accuracy of the order of <2mm

Question 33

what receptors are involved in interdental detection?

Answer 33

- periodontal ligament mechanoreceptors | - muscle spindles

Question 34

what receptors are involved in repositioning test?

Answer 34

- muscle spindles - TMJ receptors - Not PDLM's -no tooth contact