Muscle Physiology

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Muscle Physiology

Skeletal muscle - long cylindrical cells, many nuclei per cell, STRIATED, Voluntary, rapid contractions

Cardiac Muscle - Branching cells, one or two nuclei per cell, STRIATED, involuntary, medium speed contractions

Smooth muscle - Fusiform cells, one nucleus per cell, NONSTRIATED, involuntary, slow wave-like contraction

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Muscle Contraction

Nerve impulse reaches myoneural junction

Acetylcholine released from motor nerves and bind with receptors which allow sodium to enter

Sodium generates an Action Potential which travels down the T tubule.

Sacroplasmic reticulum releases calcium which bind with Troponin, Binding sites in the Actin filament are exposed.

Mysosin head attached to bind sites, creates a power stroke.

ATP energises Myosin head for other contractions. Action potentials cease. the muscle stops contracting

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Motor Unit

Creatine stores ATP

Creatine and Atp---- Creatine Phosphate and ADP

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Muscle Fatigue

Lack of O2 - ATP deficit

Lactic acid builds up from anaerobic respiration

Muscle Atrophy

weakening and shrinking of a muscle - immobilisation, loss of neural stimulation

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Muscle Hypertrophy and Tonus

Enlargement of a muscle, more capillaries, more mitochondria

caused by steroids and exercise which stimulate muscle growth and hypertrophy

Muscle Tonus - tightness of a muscle, some fibres always contracted

Tetany - sustained contraction - result of rapid sucession of nerve impulses

Refractory period - Brief period of time in which muscles cells will not respond to a stimulates

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Types of contraction

Isometric Contraction - produces no movement, used in standing, sitting posture

Isotonic contraction - produces movement, walking or moving any part of the body

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