Muscle – CSM 1040 Dr. Melanie Osterhouse

Muscle – CSM 1040Dr. Melanie Osterhouse Fxn of m – skeletal m. is about 40% of body mass a. b. c. d.

Types

Location and function • Smooth – walls of hollow visceral organs like stomach and bladder • Forces fluids thru • Cardiac – only in heart • Pumps blood • Skeletal • movement

Functional characteristics • Excitability • Contractility – unique to m. • Extensibility • elasticity

Histology (slide 127) • Bundle of sticks (m. fibers) surrounded by C.T. called ___________ • A cluster of perimysium-surrounded bundles- is surrounded by dense irregular C.T. called __________ • _______ - plasma membrane of m. fiber • ________- m. fiber cytoplasm • ________- each m. fiber composed of ______ • Each m. has 1 n., 1 a., 1 v. – enters center of m. and branch through the CT sheets

Slide 130 and 129 • Explain thick and thin filaments and bands • Thick are _______ and thin are ______ • (do people demo) • Thin filament is troponin and tropomyosin • Tropomyosin blocks myosin heads from binding • Troponin binds Ca2+

Slide 133 + 132 • Action potential -> Ca2+ release -> C12+ binds to troponin -> troponin exposes binding site for thick filament -> ATP hydrolyzed so myosin head binds -> ADP + P released -> myosin head rotates causing contraction -> ATP binds to myosin -> myosin head released from actin and recocks

Where does all the ATP come from? • Regeneration of the hydrolyzed ATP • ____________ - high energy molec stored in m • ________ +ADP->creatine +ATP • __________- makes lactic acid (m. soreness) • After creatine is used up • Break down ________ stored in m. • For large amts of ATP for moderate periods (40 sec) • ______ - prolonged light to moderate exercise • Occurs in mitochondria

Aerobic • Where does the O2 come from • _____- similar to Hb but in m. ->stores o2 • Glucose +o2 -> CO2 +H2O +ATP • 36 ATP per glucose but sluggish due to many steps

m. fatigue • Cannot contract m. even if still being stimulated (not just tired) • ________ - no ATP to unhook cross bridge = stays contracted (ex. Rigor mortis – lets go when tissue breaks down, writers cramp) • _______ - extra O2 the body must take in for restorative processes • Why you rapidly breathe after stopping exercise

Motor unit • Motor unit – Motor n. and all m. fibers it supplies • When motor n. fires, all m. fibers it innervates contract • Fine motor control (eyeball) have few fibers per n. • Large m. that are less precise (hip m.) have lots of fibers per n.

Where does the Ca2+ come from (slide 128) • ____________- stores Ca2+ and releases it on demand ( during an action potential for ex.) • Surrounds each myofibril • ______- continuation of sarcolemma that conducts the impulses and orders the release of Ca2+

Terms (slide 137) • ______ moving part • _______ immovable or less moveable bone • _____ same tension (same weight) • Concentric contraction - ________ (picking up book) • Eccentric contraction - _________(putting it back) • ________- same length (not lenthen or shorten) • Adding wt. but not moving • ______- even when relaxed, m. are almost always slightly contracted

Muscle – CSM 1040 Dr. Melanie Osterhouse