Control of Movement (2)

Question 1

Describe the stretch reflex

Answer 1

Muscle spindle - proprioceptor - detects muscle length - has mechanism to regulate sensitivity
1a afferent branches - collateral to brain - collateral to alphaMN to agonist muscle (e.g. quadriceps) - collateral to inhibitory neuron to antagonist muscle (e.g. hamstrings)

Question 2

Describe the Golgi tendon reflex

Answer 2

Golgi tendon organ - proprioceptor - detects muscle tension - no mechanism to regulate sensitivity
1b afferent branches - collateral to inhibitory 1b interneuron to agonist via alphaMN (at least disynaptic) - collateral to excitatory 1b interneuron to antagonist via alphaMN (disynaptic/trisynaptic)
Other inputs converge onto inhibitory interneuron

Question 3

Define motor pool

Answer 3

All MNs that innervate a muscle

Question 4

What are the 3 zones of the grey matter of the spinal cord and which laminae do they each involve?

Answer 4

Dorsal - I-VI
Intermediate - VII
Ventral - VIII-IX

Question 5

What is the Renshaw circuit and what is its role?

Answer 5

Recurrent inhibition - negative feedback system - not reflex
Modulates MN sensitivity
Increases antagonist activity - decreases agonist activity

Question 6

What are the two aspects of the stretch reflex?

Answer 6

Short-latency response - involuntary - via spinal cord - fast
Long-latency response - voluntary - via brain - requires processing - slow

Question 7

When does the soleus stretch reflex give the largest response and what is its purpose?

Answer 7

When foot touches ground during walking

Reinforces muscle activity

Question 8

What is the purpose of alpha-gamma coactivation and how does it work?

Answer 8

Gamma system enables muscle spindle to always respond
Stretch muscle - stretches muscle spindle - 1a afferent fires more rapidly
Muscle released from stretch - contracts - muscle spindle becomes slack - no signalling via 1a afferent
Gamma MNs fire - muscle spindle contraction - restores sensitivity to muscle length

Question 9

Where is the central pattern generator for locomotion and what is it modulated by?

Answer 9

Neural network in lumbar spinal cord

Modulated by descending supraspinal commands

Question 10

Define the cutaneomuscular reflex

Answer 10

Electrically-elicited reflex activity in active muscle

Question 11

What types of information are carried by the spinocerebellar pathway?

Answer 11

Proprioception, light and strong touch, nociception, temperature