Anatomy and Physiology Answer Key

5 oxygen supply is increased by increased rate and

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Unformatted text preview: accumulated) to the liver, where it is metabolized to CO2 and water. Without dystrophin there is no structural link between the muscle fibers and the extracellular matrix. Calcium penetrates the plasma membrane (sarcolemma) of the muscle cells and damages them, eventually destroying the muscle cells (fibers). The Sliding Filament Theory (page 59) 1. Anatomy and Physiology 2. 3. (a) Myosin: Has a moveable head that provides a power stroke when activated. (b) Actin: Two protein molecules twisted in a double helix shape that form the thin filament of a myofibril. (c) Calcium ions: Bind to the blocking molecules, causing them to move and expose the myosin binding site. (d) Troponin-tropomyosin: Bind to actin molecule in a way that prevents myosin head from forming a cross bridge. (e) ATP: Supplies energy for flexing of the myosin head (power stroke). (a) By changing the frequency of stimulation, so that fibers receive impulses at a greater rate (frequency summation). (b) By changing the number and size of motor units recruited (a few motor units = a small contraction, maximum number of motor units = maximum contraction). (a) Calcium ions and ATP. (b) Calcium ions are released from a store in the sarcoplasmic reticulum when an action potential arrives. ATP is present in the muscle fiber and is hydrolyzed by ATPase enzymes on the myosin. Muscle Tone and Posture (page 63) 1. (a) Muscle tone is the continuous and passive partial contraction of muscles giving a firm appearance. (b) At any one time, a few fibers in a muscle are always contracting involuntarily (different fibers at different times). 2. (a) The muscle spindle organ monitors the degree of stretch (contraction) in a muscle and provides information to bring about adjustment of contraction. (b) Intrafusal fibers parallel to extrafusal fibers: When the muscle relaxes, it lengthens and the muscle spindle is stretched. The stretching results in a reflex adjustment of contraction (usually to maintain tone). Sensory neurons in non-contractile region: When non-contractile portion is stretched (it cannot, its...
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This document was uploaded on 01/28/2014.

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