COGS 17 Lecture Notes - Lecture 12: Myocyte, Protein Filament, Proprioception
21 Feb 2017
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Actin = thin protein filament, a coiled double-strand braid, anchored to muscle. Note: this is the only mono-synaptic reflex onto relevant flexor muscles to move body part way from noxious stimulus that inhibit the motor neurons causing that contraction, lessening their rate of firing. Come in antagonistic pairs: flexor moves bone toward body, extensor move same bone from body. Usually 1 axon branches to multiple muscle fibers; the fewer fibers per axon the more precise the control. So note, the only active muscle response is contraction all stretch is passive. (e. g. while walking, lifting, being tapped on knee by a doctor testing your reflexes , etc. ) Axon of spindle to spinal cord, excites motor neuron back to same muscle, contracts to counter stretch. Myosin = thick protein filament with knobby bead-like clusters ( cross bridges ) along it, and. Contraction = myosin cross bridges hook into (grab) coiled actin, bend to tighten coil, release, repeat.
