Proprioception

Question 1

What are proprioceptors?

Answer 1

mechanoreceptors that signal body or limb position

Question 2

What are the 3 types of proprioceptors?

Answer 2

muscle spindles
golgi tendon organs
joint receptors

Question 3

What do muscle spindles do?

Answer 3

monitor muscle length and rate of change of muscle length i.e control reflexes and voluntary movements

Question 4

What do Golgi Tendon Organs do?

Answer 4

monitor tension on tendons

Question 5

What do joint receptors do? (3 things)

Answer 5

monitor joint angle, rate of angular movement and tension on the joint

Question 6

What 2 structures form the muscle spindle?

Answer 6

intrafusal fibres and extrafusal fibres (which means that they are different types of muscle CELL)

Question 7

How do muscle spindles lie in relation to muscle fibres?

Answer 7

lie in parallel

Question 8

Describe the muscle spindle.

Answer 8

• nuclear chain and nuclear bag fibres are the two types of intrafusal fibres with afferent nerves called the annulospiral wound around them (primary afferents)
• secondary afferent endings form flower spray endings
• intrafusal fibres enclosed in capsule and surrounded by extrafusal muscle fibres
• ends of intrafusal fibres contain sarcomeres and are contractile - gamma motor neurones innervate these

Question 9

What neurones innervate the extrafusal fibres?

Answer 9

gamma motorneurones

Question 10

What happens when the muscle stretches?

Answer 10

the spindle stretch receptors are activated
stretch sensitive ion channels open causing a local generator potential which causes regenerative action potentials on the afferent fibres

Question 11

What does the resting AP frequency depend on?

Answer 11

length Lzero

Question 12

What does contraction of the agonist muscle do to spindle discharge?

Answer 12

reduces it

Question 13

What does lengthening of antagonist do to spindle discharge?

Answer 13

increases it

Question 14

What is the significance of gamma motor neurone innervation of the muscle spindle at the ends of the intrafusal fibres?

Answer 14

allows the intrafusal fibres to contract and to not go ‘floppy’ therefore maintain sensitivity

Question 15

What is the significance of alpha/gamma motor neurone coactivation?

Answer 15

alpha motor neurones fire causing extrafusal fibre contraction and the gamma motor neurones fire causing intrafusal fibre ends to contract
- restores tension and resets sensitivity of central sensory part of intrafusal fibres at a new muscle length