2008 Motor output

2008 Motor output - Moving the joints Moving joints Joints...

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Unformatted text preview: Moving the joints Moving joints Joints are moved by reciprocal action of muscles- flexors and extensors. Nervous system is wired to facilitate this. Stretch reflex results in contraction of the stretched muscle and relaxation of antagonist. This is referred to as the Reciprocal innervation pattern . Flexor reflex results in limb withdrawal via excitation of flexors and inhibition of extensors. Opposite effects on contralateral limb. The Stretch Reflex Reciprocal Control of Antagonist Muscles Changing the sign of synaptic action Inhibitory projection to antagonist muscles results in reciprocal relaxation of antagonistic muscles. Requires an inhibitory interneuron that is activated by the same fibers that excite the motoneurons to the muscle that is stretched. The excitatory transmitter is glutamate. The inhibitory interneuron releases a transmitter (glycine) that inhibits antagonist motoneurons. Each motoneuron has receptors to both glutamate and glycine which together determine its susceptibility to reach action potential threshold depending on the degree of activation of the opposing receptors. Negative Feedback From Muscle Spindles Muscle spindle measures muscle length and this signal is converted to motoneuron depolarization leading to muscle shortening.shortening....
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2008 Motor output - Moving the joints Moving joints Joints...

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