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170
what is the stretch reflex?
how does it function?
how does it function?
negative feedback mechansim to resist pssive change in muslce length. if stretched, then contracts extensor to counteract lenghening which is achieved on tapping the muscle e.g. in jerk reflex wich a little hammer on the patellar tendon (quadriceps femoris)
- 1a afferent senses change
- start to fire ap
- synaoses with alpha motor neuron in ventral horn
- apha motor neuron sends impulse back to extrafusal muscle fibres to contract
- type 2 ribres terminat on interneurons, transmit delayed signals to anteror horn
- 1 a afferent also sends signals to an interneuron (inhibitors) which synapses with motor neuron of flexor muscle (antagonist)
- initiates inhibition of flexor muscle, so movement is only extension
- descending pathways coactivate alpa and gamma neurons, gamma neuron make endportion contract of intrafusal mucle fibre
- so takes slack out of the spindle
- as a reflex pathway, does not involve brain too much, only gets commanding signals
- 1a afferent senses change
- start to fire ap
- synaoses with alpha motor neuron in ventral horn
- apha motor neuron sends impulse back to extrafusal muscle fibres to contract
- type 2 ribres terminat on interneurons, transmit delayed signals to anteror horn
- 1 a afferent also sends signals to an interneuron (inhibitors) which synapses with motor neuron of flexor muscle (antagonist)
- initiates inhibition of flexor muscle, so movement is only extension
- descending pathways coactivate alpa and gamma neurons, gamma neuron make endportion contract of intrafusal mucle fibre
- so takes slack out of the spindle
- as a reflex pathway, does not involve brain too much, only gets commanding signals
