VertPhys21 - Lecture 21: Spinal Cord and Brainstem...

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Lecture 21: Spinal Cord and Brainstem Circuits: Input from Motor Cortex and Brainstem centers into Motor neuron pools and local circuit neurons. Motor neuron pools send info to skeletal muscles. Local circuit neurons send input to motor neuron pools and also sensory inputs. Motor Cortex and Brainstem Centers receive input from Basal Ganglia and Cerebellum To lift a glass while someone is pouring liquid into it: Motor neuron: gets descending facilitation and inhibition, tells muscle to flex/inhibit amount needed to hold glass. DISTURBANCE (water poured in)—length change in muscle fiber is sensed by Spindle Receptor which then tells the Motor neuron (via spindle afferent discharge), which then tells muscle how much to change force. Flexion Reflex: When you step on a sharp object: Cutaneous receptor stimulated cutaneous afferent fiber from nociceptor sends signal to interneurons, which are connected to motor neurons connecting to that leg and other leg, stimulated leg flexes while opposite leg extends! Otherwise you would fall over. Kitten walking: -detecting AP through skin: -when flexion muscle fibers fire, extensor muscle fibers are inhibited -APs of thousands of muscle fibers -basic coordination (locomotion- extensor and flexor coordination)- is intrinsic within spinal cord -motor movement does not have any real start; network at all times Error correction: Motor Cortex: planning, INITIATING, and directing voluntary movements; input from basal ganglia (gating proper initation of movement)
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This note was uploaded on 07/31/2009 for the course BIO 365R taught by Professor Draper during the Spring '08 term at University of Texas at Austin.

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VertPhys21 - Lecture 21: Spinal Cord and Brainstem...

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