Proprioception Flashcards
what is proprioception?
awareness of position of body parts in relation to each other and surroundings
what is movement awareness?
kinaesthesia
what receptors are involved in proprioception?
muscle spindles
golgi tendon organs
joint receptors
what are the types of muscle fibres?
extrafusal
intrafusal
what muscle fibres make up the bulk of the muscle fibres and are contractile?
extrafusal
where do intrafusal muscle fibres exist?
extrafusal
muscle spindles
specialised muscle fibres
CT capsule
what are there in and around teeth instead of tendon organs?
stretch receptors in the PDL
describe the structure of an intrafusal
muscle fibre
contractile end portion
non-contractile central portion (can be stretched)
contractile end portion
what are afferents in intrafusal fibres activated by?
stretch
what is the role of secondary nerve endings in the intrafusal fibre?
detects length of fibres
what is the role of primary annulo-spiral nerve endings in extrafusal fibres?
detects length of fibres and speed of change of length
what neurones are in the efferent part of the intrafusal
fibre?
gamma motor neurone
what neurones supply extrafusal fibres?
alpha motor neurones
what is the role of a muscle spindle?
information about muscle length
acts to maintain muscle length
jaw jerk reflex
where are masticatory muscle spindle cells bodies?
mesencephalic nucleus
where to masticatory muscle spindle afferents synapse?
trigeminal motor nucleus
cerebellum
cerebral cortex
what motor neurons are active when muscle contracts?
alpha motor neurones
gamma motor neurones
what is the role of gamma motor neurons in masticatory muscle spindles?
- Cause contraction of intrafusal fibres
- Maintain tension in spindle.
- Maintain spindle afferent activity.
**So spindles always work
Load compensation in the jaw
what co-activates when muscles shorten?
alpha and gamma motor neurones
what happens during alpha gamma coactivation?
- Muscle shortens.
- Spindle tension maintained.
- Spindle activity maintained.
what happens on resistance on biting?
- Muscle doesn’t shorten.
- Gamma activity stretches spindle.
- Spindle activity increases.
- Alpha drive to muscle increases.
what is the role of golgi tendon organs?
In tendons in series with muscle fibres.
There are very few in masticatory muscles.
They are tension receptors and have a role in inhibitory reflex, preventing of stretch of muscle.
what are pacinian joint receptors for?
in ligaments for acceleration
what are golgi joint receptors for?
in ligaments for position
