Receptors and spinal control

Question 1

Deafferentation

Answer 1

Patient GL: Deafferentation caused by demyelination of large diameter peripheral nerves responsible for touch and proprioception.

Without vision, Patient GL makes inaccurate, jerky
movements with large errors.

Question 2

knee jerk reflex

Answer 2

to aMN on homonymous muscle, one synapse, straight to. inhibitory dumps GABA over an interneuron

1. Tendon tap rapidly lengthens the
   quadriceps muscle.
2. Stretch of quadriceps muscle
   lengthens intrafusal fibers, causing
   spindle to fire action potentials.
3. Spindle afferents enter the spinal
   cord via the dorsal horn.
4. Sensory neuron synapses on and
   excites alpha motor neuron (AMN).
5. Excitation of AMN causes reflex
   contraction of quadriceps.
6. Sensory neuron also synapses on
   inhibitory interneuron, which
   inhibits AMN of antagonist muscle
   (reciprocal inhibition).
7. Hamstring (antagonist) is inhibited.
8. Information is sent to the brain

Question 3

Recordings from different points

Answer 3

Estimates of the time difference between the onset of activity in the stretched muscle and inhibition of the shortened muscle confirm that reciprocal inhibition is mediated by a single inhibitory interneuron

Question 4

Stretch of agonist muscle produces reflex contraction of ——- muscles and ——— muscles
and inhibition of it’s ——–

Answer 4

homonymous
synergist
antagonist

Question 5

whats the point of gamma motor neurons

Answer 5

CO ACTIVATION

This means muscle spindles would lose their sensitivity
during voluntary movements

How do gamma motor neurons help maintain spindle
sensitivity to measure unexpected changes in muscle
length during voluntary movements?

GMNs stimulate intrafusal muscle fibers. This maintains the length of intrafusal fibers and spindle sensitivity during voluntary muscle contractions/movements