Lecture 21 - Receptors and Spinal Control of Somatosensory feedback Flashcards
What happens with deafferentiation caused by myelination of large diameter peripheral nerves?
Most commonly acute inflammatory demyelinating polyneuropathy
Without vision, can no long sense where limbs are in the air
inaccurate, jerky movements with large errors are made
What do gamma motor neurons do?
Ensure that the intrafusal stretch with extrafusal fibres so that muscle spindle can continue working
What happens to the firing rate of muscle spindles when muscle is stretched?
Increased firing rate
Muscle spindles
What happens to the membrane potential, APs and release of NTs with longer and larger stimuli?
greater change in membrane potential
more APs
more NTs released
How many synapses are in a simple stretch reflex like the knee jerk reflex?
Afferent to efferent
1 synapse
Describe what occurs in a knee jerk reflex.
- tendon tap rapidly lengthens the quadriceps muscle
- stretch of quadriceps muscle lengths the intrafusal fibers, causing the spindle to fire an AP
- Spindle afferents enter the spinal cord via the dorsal horn
- Sensory neuron synapses on and excites alpha MN
- excitation of alpha MN causes reflex contraction of quadriceps
- sensory neuron also synapses on inhibitory interneuron, which inhibits alpha MN of antagonist muscle (reciprocal inhibition)
- hamstring. (antagonist) is inhibited
- information is sent to the brain
Knee jerk reflex
How long does it take from when the force is applied to when muscle activity is generated?
20-25 ms
What does the latency of neural responses depend on?
the # of synapses involved
Does the onset of activity in the stretched muscle and inhibition of shortened muscle occur at the same time?
No, inhibition occurs shortely after indicating that reciprocal is mediated by a single inhibitory interneuron
What does homonymous muscle mean?
In the same muscle stretched by the stimulus
