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

Types m. TypeInvoluntaryVoluntaryStriatednonstriated Smooth cardiac skeletal

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  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