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8_Unit2.3_Somatosensation copy

E muscles tendons joint capsules and ligaments there

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Unformatted text preview: s from the musculoskeletal system (i.e., muscles, tendons, joint capsules and ligaments) there are many kind also in joints stretch==velocity •  Proprioceptors are low threshold mechanoreceptors that inform CNS about movement and position by detecting the stretch of the tissue in which they lie. 7 7/4/12 UNDERSTAND!!!!! Muscle Spindle •  Cigar-shaped (fusiform) structures that run in parallel to regular (extrafusal) muscle fibers muscle spindles--fusiform(cigar shaped) run parralel to muscle fibers. they are INTRAFUSAL FIBERS!!!!!!! these sense forces extrafusla fibers produce force ---they are both in the freaking muscles!!!!! -high position fine motor skills like vision and touch are filled with many intrafusla fibers like spindles!!!!!!!!!!! quads dont have them so densly packed because its gross Muscle Spindle •  Density of muscle spindles vary from muscle to muscle. •  Muscles used for precision movements (extraocular eye muscles, intrinsic muscles of the hand and small muscles in the neck joints) have a higher density of spindles. KNOW THIS WILL BE TESTED!!!!!!!!!!!!!!!!!! Muscle Spindle know what innervates what!! extrafusal muscle innervated by the alpha (α) motor neuron Intrafusal muscle innervated by the gamma (γ) motor neuron 8 7/4/12 know the second bullet point!!!!!!!! Muscle Spindle low threshold mecanoreceptors •  Intrafusal muscle fibers only show striations at their ends and therefore can only contract in these areas •  There are two types of sensory fibers that monitor the intrafusal muscle. Both are slow adapting, low threshold mechanoreceptors. "  secondary afferent mechano recptors have to be stimulated by---mechanical stimulus primary afferent "  mean the action potential is easier to obtain. it doesnt have to depolarize as much---so the stimulus can be much less. a photorecptor for example needs--- duh light photons son Sensitivity of the muscle spindle •  Muscle spindle afferents respond to stretching of the intrafusa...
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