N19- Trigeminal proprioception Flashcards
what is proprioception?
Awareness of position of body parts in relation to each other and surroundings
what is kinaesthesia?
movement awareness
what receptors are involved in proprioceptors?
- muscle spindles
- golgi tendon organs
- joint receptors
Describe the extrafusal fibres.
- bulk of the muscle fibres
- contractile
Describe the intrafusal fibres.
- muscle spindles
- specialised muscle fibres
- within a ct capsule
how do muscle spindles lie in comparison to muscle fibres?
lie parallel to each other
how do the muscle itself and muscle spindles contract?
contract independent of one another as they have a different nerve supply
Describe the structure of the muscle spindle.
Both ends of the spindle are contractile and there is a non-contractile central portion which can be stretched
How are the afferents activated in muscle spindles?
activated by stretch
what does the primary annulo-spiral nerve ending detect?
Detects length of fibres and speed of change of length
what does the secondary (flower-spray) nerve endings detect?
detect length of fibres
what is the efferent neurone of the muscle spindles?
Gamma motor neurone
what are the extrafusal fibres supplied by?
alpha motor neurons
what is the muscle spindle role?
- Information about muscle length
- act to maintain muscle length
- load compensation
what happens when muscle spindle is stretched during reflexes?
muscle spindle contracts to maintain original position
Describe the spindles in action with the water bucket scenario .
- Bucket fills with water
- Biceps spindles stretch
- Increased motor neurone drive to biceps
- Muscle length maintained
where are muscle spindle cell bodies found?
trigeminal mesencephalic nucleus
where do muscle spindle afferents synapse?
- V motor nucleus
- Other areas linked to sensorimotor regulation: cerebellum and cerebral cortex
what happens when the muscle shortens?
- Contract muscle spindles using gamma motor fibres
- drives the length of extrafusal muscle during contractions
what are the roles of gamma motor neurones?
- Cause contraction of intrafusal fibres
- Maintain tension in spindle
- Maintain spindle afferent activity
- α‐γ co‐activation
During load compensation, what happens during α‐γ co‐activation?
- muscle shortens -jaw closes
- spindle tension maintained
- spindle activity maintained
- (muscle is not changing length, just force increasing)
During load compensation, what overcomes the resistance of the carrot?
- muscle doesn’t shorten
- γ-activity stretches spindle
- spindle activity increased
- α drive to muscle increases
what prevents teeth crashing together during load compensation?
The length of intrasfusal fibres causes activation of jaw opening muscles
where are more spindle fibres found in skeletal muscle?
in places for more fine motor control, detailed movements i.e the hand
where are Golgi tendon organs found?
in tendons in series with muscle fibres
where are very few, if any, Golgi tendons organs?
masticatory muscles
what type of receptors are golgi tendon organs ?
tension receptors
what role does Golgi tendon organs have?
Role in (inhibitory) reflex ‐prevention of XS stretch of muscle
what does Golgi tendon do in response to muscle moving against great resistance?
starts firing to offer feedback to muscle system which controls the amount of force you can generate from that muscle to prevent muscle damage
what plays the equivalent role to Golgi tendon in the mouth?
receptors in periodontal ligament provide the same feedback in the mouth
where are the 3 joint receptors , where are they found and what is their role?
-Pacinian – in ligaments ‐ acceleration
- Golgi – in ligament ‐ position
- Ruffini ‐ in capsule‐ movement
Name a test of proprioceptive ability?
- interdental detection - can detect 50micrometers between teeth
- ability to reposition the jaw -accuracy of the order of <2mm
what receptors are involved in interdental detection?
- periodontal ligament mechanoreceptors
- muscle spindles
what receptors are involved in repositioning test?
- muscle spindles
- TMJ receptors
- Not PDLM’s -no tooth contact
