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Muscle Physiology Human Anatomy and Physiology II Oklahoma City Community College Dennis Anderson Muscle Tissue • Skeletal Muscle • Cardiac Muscle • Smooth Muscle 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 contractions Microanatomy of Skeletal Muscle Z line Z line H Band Sarcomere Relaxed Sarcomere Partially Contracted Sarcomere Completely Contracted Binding Site Troponin Tropomyosin Myosin Neuromuscular Junction Acetylcholine Opens Na+ Channel Muscle Contraction Summary • Nerve impulse reaches myoneural junction • Acetylcholine is released from motor neuron • Ach binds with receptors in the muscle membrane to allow sodium to enter • Sodium influx will generate an action potential in the sarcolemma Muscle Contraction Continued • Action potential travels down T tubule • Sarcoplamic reticulum releases calcium • Calcium binds with troponin to move the troponin, tropomyosin complex • Binding sites in the actin filament are exposed Muscle Contraction Continued • Myosin head attach to binding sites and create a power stroke • ATP detaches myosin heads and energizes them for another contaction • When action potentials cease the muscle stop contracting Motor Unit All the muscle cells controlled by one nerve cell Motor Unit Ratios • Back muscles – 1:100 • Finger muscles – 1:10 • Eye muscles – 1:1 ATP Creatine • Molecule capable of storing ATP energy Creatine + ATP Creatine phosphate + ADP Creatine Phosphate • Molecule with stored ATP energy Creatine phosphate + ADP Creatine + ATP Muscle Fatique • Lack of oxygen causes ATP deficit • Lactic acid builds up from anaerobic respiration Muscle Atrophy • Weakening and shrinking of a muscle • May be caused – Immobilization – Loss of neural stimulation Muscle Hypertrophy • Enlargement of a muscle • More capillaries • More mitochondria • Caused by – Strenuous exercise – Steroid hormones Steroid Hormones • Stimulate muscle growth and hypertrophy Muscle Tonus • Tightness of a muscle • Some fibers always contracted Tetany • Sustained contraction of a muscle • Result of a rapid succession of nerve impulses Tetanus Refractory Period • Brief period of time in which muscle cells will not respond to a stimulus Refractory Refractory Periods Skeletal Muscle Cardiac Muscle Isometric Contraction • Produces no movement • Used in – Standing – Sitting – Posture Isotonic Contraction • Produces movement • Used in – Walking – Moving any part of the body Myoglobin • Oxygen carrying protein related to hemoglobin • Found in skeletal & cardiac muscle • Store O2 • Allows for organisms to hold their breath longer • May be found in blood stream if muscles have been damaged ex: after a heart atta THE END
