Muscle Spindle - spinal cord Muscle Spindle * consist of...

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spinal cord Muscle Spindle * consist of modified muscle fibers ( intrafusal fibers to distinguish them from extrafusal fibers , i.e. the rest of the muscle) * only the two ends of an intrafusal fiber have sarcomeres and are able to contract * middle portion acts as a stretch receptor Muscle Spindle Two types of intrafusal muscle fibers based anatomically on the location of their nuclei * Nuclear bag- the nuclei hang out in the center of the fiber, which bulges out into a bag. * Nuclear chain- the nuclei spread out along the fiber like a chain. * only the ends of the intrafusal fibers contain sarcomeres and are able to contract Have three types of nerve fibers * Both contain primary afferent nerve fibers (Ia) which end in annulospiral fibers that coil around middle that respond mainly to muscle stretch * secondary afferent nerve fibers wrap primarily around the ends of nuclear chain fibers that respond mainly to prolonged strecth * gamma motor neurons fibers which innervate the ends of the intrafusal fibers
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This note was uploaded on 01/30/2012 for the course BSC BSC1085 taught by Professor Sharonsimpson during the Fall '10 term at Broward College.

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Muscle Spindle - spinal cord Muscle Spindle * consist of...

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