1. Muscle Physiology
Chapter 11

2. 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

4. 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

6. Sarcomere Contractile unit of a muscle fiber
each myofibril consists of many sarcomeres
Z line
Anchors thin filaments
Boundary of sarcomere
M line – anchors thick filaments
A band: segment of thick & thin filaments
I band: segment of thin filaments
H zone: where thin and thick filaments will not overlap (only thick)

8. Sarcomere cont… Elastic filaments – connect thick filaments to Z line
T (transverse) tubules – allows impulses traveling along sarcolemma to move deeper within the cell
Triad – t tubule sandwiched between sacs of the SR
Allows impulses traveling along a t tubule to stimulate sacs of the SR

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

11. 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

13. Muscle Excitation
Nerve impulse reaches the end of a motor neuron  releases acetylcholine (Ach)
Ach diffuses across the neuromuscular junction and binds with the receptors on the motor endplate

14. Muscle Contraction
Impulses travel along the sarcolemma  t tubules  sacs of SR
Ca2+ is released (balloons to distract)into the sarcoplasm  binds with troponin(chaperone)
Tropomyosin shift to expose actin’s active site
Energized myosin (Boy) KISSES (bind) with actin’s(girl) active site and pulls (her to middle of the dance floor)thin filament towards center of sarcomere
Requires ATP

17. 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

19. Rigor Mortis “stiffness of death”
SR releases excess Ca2+  myosin heads bind with actin’s active sites  contraction of myofilaments
Lack of ATP after death causes cross bridges to “stick”

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21. Alternate Source of Energy
ATP must be continually re-synthesized
Breakdown of creatine-phosphate (CP) provides energy for ATP re-synthesis
Catabolism of food provides energy for ATP and CP synthesis

22. 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

23. Heat Production Some energy from catabolic processes is lost as heat
Muscle release massive amts of heat
Thermoreceptors sense decrease in body temp  hypothalamus integrates information  signal sent to skeletal muscle to contract  shivering  homeostatic balance is maintained

25. 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