CAPS 301 Lecture Notes - Lecture 10: Quadriceps Femoris Muscle, Stretch Receptor, Reciprocal Inhibition
15 Oct 2018
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Single group ia fibre (phasic change) enters each spindle. Forms spiral endings around all (both bag and chain) intrafusal fibres. Rapidly adapting: signal rate of change of length. Several group ii fibres (absolute length) enter each spindle. These are secondary endings (network/mesh over chain fibres) Intrafusal fibres have motor innervation via gamma-motor neurons. Monosynaptic neurons: doesn"t mean only 1 synapse, means that there is one interneuron. If muscle were lengthened, it would increase ap firing in group ia, which increases firing of alpha-mn, and activates nmj. Bicep contracts, so intrafusal fibres in biceps shorten. As you shorten through a range of motion, the intrafusal fibres have the potential to become slack (no longer elastic) We want a system where over the full range of motion for the muscle, the sensory fibres never go slack. Alpha-gamma coactivation (makes sure spindles don"t go slack, and still get length information)
