ANAT 312 Lecture Notes - Lecture 2: Upper Motor Neuron Lesion, Corticospinal Tract, Tectospinal Tract
26 Nov 2016
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Muscle spindles: primary spindles largely respond to velocity of stretch. Some firing to increased length: secondary spindles largely respond to muscle length (and to a lesser degree velocity), gamma motor neurons these are the smallest motor neurons. Innervate the muscle intrafusal fibres and change the excitability of spindle responses how we are able to perform gross and fine motor movements. Deep tendon reflex: monosynaptic excitation of muscle agonist and disynaptic inhibition of antagonist. Reflex response and circuitry tests are useful for neurological examinations. Primary spindle afferents go centrally to the drg in the spine and then to motor neurons. They are processed and sent back to the primary muscle to cause a reflex. At the same time motor axons from the ventral root are synapsing on inhibitory neurons that are going to antagonist muscles. Excitation of muscle agonists in the tricep but inhibition of muscle antagonists in the bicep in a tendon tap = extension.
