Muscle Physiology Chapter 11

Connective Tissue Components Muscle cell = muscle fiber Endomysium – covers muscle fiber Perimysium – binds groups of muscle fibers (fasicles) Epimysium – covers the entire muscle Tendon – fibrous tissue that connects muscle to bone Aponeurosis – broad, flat sheet of connective tissue Fascia – fibrous CT surrounding muscle and tendon

Overview of Muscle Cell Muscle cell = muscle fiber Sarcolemma = plasma membrane Sarcoplasm = cytoplasm Sarcoplasmic reticulum (SR) = network of tubules and sacs Multi-nucleated, multiple mitochondrion Bundles of myofibrils extend lengthwise & fill sarcoplasm Composed of thick and thin myofilaments

Sarcomere Contractile unit of a muscle fiber each myofibril consists of many sarcomeres

Myofilaments Myofibrils – made up of 1000s of thin and thick myofilaments Thin filaments Actin Tropomyosin Troponin Thick filaments myosin

Actin molecules strung together like beads to form two fibrous strands that twist around each other Actin and myosin molecules have a chemical attraction to each other At rest – actin active sites are covered by tropomyosin; tropomyosin held in place by troponin Myosin filaments – heads stick out from bundles; attracted to actin

Muscle Relaxation Nerve impulse is complete  Ca2+ is pumped back into the sacs of the SR Ca2+ is stripped from the troponin  tropomyosin covers the actin’s active site Myosin heads can no longer bind with actin  muscle fiber returns to its resting length

http://www.sci.sdsu.edu/movies/actin_myosin_gif.html

Rigor Mortis “stiffness of death” Lack of ATP after death causes cross bridges to “stick”

http://highered. mcgraw-hill http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter9/

Aerobic vs. Anaerobic Respiration Oxygen-requiring process Produces maximum amount of ATP from one glucose molecule Anaerobic Respiration Does not require oxygen Short-term, rapid process to re-synthesize ATP Produces lactic acid Burning/soreness in muscles

http://natchem.files.wordpress.com/2009/11/motor-unit-lg.jpg

Isotonic vs Isometric Contractions Isotonic – tension remains the same; length of the muscle changes Concentric contraction: muscle shortens (contracts) Eccentric contraction : muscle lengthens Isometric – tension changes; length of the muscle remains the same Myosin heads unable to move thin filaments Static tension