NESC 2470 Lecture Notes - Reciprocal Inhibition, Golgi Tendon Organ, Superior Colliculus
26 Nov 2012
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Inside composed of muscle fibres: type 1a sensory axon wrapped around each fibre. Information conveyed by 1a afferent axon into spinal cord. Could potentially contact every alpha motor neuron in the motor pool supplying the muscle in which the spindle resides. Alpha motor neurons were still intact, but reflex disappeared: faster firing rate as muscle lengthens, type 1a afferent axons important. Discharge is closely related to the length of the muscle. Hitting tendon on knee causes quad contraction and knee straightens: because it causes tendon to stretch, opening mechanosensitive ion channels. Receive motor innervation from gamma motor neurons: another type of lower motor neuron, gamma activation alone increases ia activity. Innervate the intrafusal muscle fiber at the two ends of the muscle spindle. When not receiving signal (when muscle is slack) Muscle tightens to begin receiving signal again. Gamma motor neuron -> intrafusal muscle fiber -> ia afferent axon -> alpha motor neuron -> extrafusal muscle fiber.
