BISC306 Lecture Notes - Lecture 20: Extrafusal Muscle Fiber, Intrafusal Muscle Fiber, Afferent Nerve Fiber
4 Apr 2017
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Neural basis of simple reflexes: a muscle is controlled by a motor neuron pool, not just one type of motor neuron b. i. Alpha motor neurons control motor units that generate force in the muscle itself b. i. 1. b. i. 2. These are the fibers that cause a muscle to contract b. ii. Gamma motor neurons control muscle spindles b. ii. 1. b. ii. 2. Muscle spindles are also innervated by stretch sensitive 1a afferent neurons b. ii. 3. In animal studies, if the dorsal root is cut the muscle does not reflexively contract: this is the basis for the patellar tendon reflex, contractions usually inhibit antagonistic muscles. Stretch reflex: descending input from the brain controls alpha and gamma motor neurons, example: control of quadriceps. Afferent signal here = error signal; less or more can have an effect. Telling it that it needs to excite this muscle more frequently: example: picking up more weight when you thought it was lighter, or vice versa e.
