Muscle reflexes: Control of posture

Question 1

How does the feedback loop work?

Answer 1

Muscle spindle detects length in a muscle
Feeds to spinal cord
sends effector to muscle

Question 2

What is a length trasnducer

Answer 2

Spindle in parallel with muscle

Question 3

What are intrafusal fibres

Answer 3

designed to monitor length in muscle

contractile elements are gone

Question 4

What innervates intrafusal fibres

Answer 4

Innervated by type 1a (thick and II (thin) for sensory inn

innervated by dynamic and static gama efferernts for motor inn

Question 5

How do fibres sense velocity

Answer 5

Fast adapting and very quickly stop firing as soon as stimulus ends
produce a phasic response

Question 6

What is meant by alpha-gamma coactivation

Answer 6

Contract muscle with alpha motor neurone also contract spindle with gamma motor meurone

Question 7

What does the alpha- gamma coactivation do?

Answer 7

Prevents spindle from being unloaded

gamma neurones can determine how toned the muscles are

Question 8

What is the stretch reflex

Answer 8

Monosynaptic reflex but recriprocal innervation
muscle contracts against stretch
smooths and damps muscle movement
signals length and velocity of muscles centrally via the spinocerabellar adn dorsal tracts

Question 9

What does the golgi tendon organ insure?

Answer 9

tendon doesn’t stretch and allows us to control muscle force finely aswell as length

Question 10

What is the crossed extensor reflex

Answer 10

An opposite side to stimulus to stiffen the body and stabilise posture

Question 11

What happens when we are walking

Answer 11

• alternate contraction of flexors and extensors

central pattern generator in spine