Muscular & Skeletal Systems

Muscular & Skeletal Systems - Skeletal and cardiac...

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Skeletal and cardiac muscle – striated Smooth muscle – involved in GI motility, constriction of blood vessels, uterine contractions, etc. Smooth & Cardiac muscle – no conscious control; innervated by the autonomic nervous system. Muscle can only contract to cause force on bones and movement. Tendons – attach muscle to bone. Contraction of the triceps has the opposite effect on the lower arm as contraction of the biceps - Antagonistic muscle movement (one relaxes while the other contracts). Both muscles are still innervated by the same neurotransmitter: acetylcholine . - We can also have synergistic motion (both muscle groups contract simultaneously) The force of contraction is dependent upon the timing of the signal - We can have temporal summation, or spatial summation - In either case, we alter the frequency of stimulation, and the amount of neurotransmitter released. Quick review: a given sarcomere is bound by two Z-lines. - Only thin filaments (actin filaments) are attached to Z-lines. - I-bands – full length of actin filaments - A-bands – overlapping myosin and actin filaments: this is where contraction is generated . Recall: The I-band and the H-zone are the two areas on a sarcomere that shorten; everything else remains the same. When the myosin head attaches to the myosin binding site on the actin, it is said to be connected by a cross-bridge . When the angle between the myosin head and tail decreases (i.e. during the power stroke), muscle contraction occurs. Sliding-filament theory: when myosin attaches to the myosin-binding site on G-actin molecules in the thin filaments: when ADP, inorganic phosphate is released, and when ATP is hydrolyzed: Review in human physiology notes. Sidenote: at the “resting position,” myosin has ADP and inorganic phosphate bound to it. Calcium is not bound to troponin, and tropomyosin continues to stay wrapped around the actin molecule to inhibit contraction . When calcium is bound to troponin, the tropomyosin moves out of the way to enable muscle contraction. - When ADP/inorganic phosphate is released, the actin chain is pulled towards the center of the sarcomere (i.e. the Z-lines come closer together) when myosin rotates on its hinge. -
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This note was uploaded on 11/07/2010 for the course CBN 356 taught by Professor Merill during the Spring '08 term at Rutgers.

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Muscular & Skeletal Systems - Skeletal and cardiac...

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