PSL300H1 Lecture Notes - Lecture 28: Reciprocal Inhibition, Motor Neuron, Proprioception

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26 Apr 2018
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Lecture 28
Central Pattern Generator (CPG): Networks of interneurons in the spinal cord and brain stem
(hypothalamus as well) and are ordered as to their relevance that coordinate the interaction of
many motor groups. This is an intermediate complexity form of control. Posture and movement
are programmed by the CPGs, or functional networks of neurons
-Stretch reflex cannot restore postural stability after perturbation of posture; cannot
provide accommodation if something were to happen to the postural stability
-Control various repetitious activities like breathing, walking, swimming.
Locomotion: walking is a cyclic pattern. In order us to walk, we had 2 networks that control our
walking located in the spinal cord in the lumbar area. The CPG for walking are:
1. Pacemaker neurons (you don’t need to think about walking) and can diffuse
excitation.
2. Reciprocal inhibition - they can inhibit one another. There are 2 CPGs for leg. One is
a flexor generator for flexion and the other is an extensor generator for extension. Both
are spontaneously active when not inhibited > no leg movement
- so when the CNS initiates a signal for CPG activation, the CPGs will turn
themselves on and off intermittently providing us the ability to walk
Step 1: Flexion phase of swing has a fixed duration of (0.25-0.3s) regardless of speed of
locomotion
Step 2: Flexor burst network (activated = flexion) has a buildup of inhibition that
eventually stops the burst of action potential, thus ending the activation of flexor
motoneurons
Step 3: The reciprocal inhibitor of extensor burst network ceases, and the extensors are
active.
Sensory feedback for adjustments:
1. reafferance
2. cutaneous - foot pressure
3. proprioceptive - muscle load
all are components that will be
used to adjust the walking cycle.
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Document Summary

Central pattern generator (cpg): networks of interneurons in the spinal cord and brain stem (hypothalamus as well) and are ordered as to their relevance that coordinate the interaction of many motor groups. This is an intermediate complexity form of control. Posture and movement are programmed by the cpgs, or functional networks of neurons. Stretch re ex cannot restore postural stability after perturbation of posture; cannot provide accommodation if something were to happen to the postural stability. Control various repetitious activities like breathing, walking, swimming. In order us to walk, we had 2 networks that control our walking located in the spinal cord in the lumbar area. The cpg for walking are: pacemaker neurons (you don"t need to think about walking) and can diffuse excitation, reciprocal inhibition - they can inhibit one another. One is a exor generator for exion and the other is an extensor generator for extension. Both are spontaneously active when not inhibited > no leg movement.

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