Ch 11-13

Epimysium=surrounds entire muscle, separates it from other tissue & sonnets to deep fascia Perimysium=divides muscle into compartments called fascicles (bundles) Endomysium=surrounds individual muscle fibers

movement (contraction pulls bones for movement), maintains posture/body position supports soft tissue, holds in place as well as protects guards openings, voluntary control of openings maintains body temp store nutrient reserves

Directly=muscle to bone (rare) Tendons=bundles of the ends of epi, peri & endo come together aponeurosis=broad sheet attachment

sarcolemma=cell membrane around muscle fiber, maintains a transmembrane potential, sarcoplasm=cytoplasm, transverse tubules=extends into sarcoplasm, filled with ECF, electrical impulses conduct into cell, myofibrils=ea. fiber contains 1000s, contains protein filaments (myofilaments), sarcoplasmic reticulum=wraps around each myofibril, is connected to t-tubules, contains lots of Ca

The smallest functional unit of muscle fiber. 10,000/myofibril. thick filaments=myosin thin filaments=actin proteins stable and regulate filaments

A band=(dArk) center of sarcomeres, length of thick filament M Line=center point of thick filament H Zone=area of thick filament with no thin filament Zone of overlap=area where thin & thick filaments overlap (darkest of dark) I Band=(lIght) thin filaments only Z lines=mark boundary b/t adjacent sarcomeres Titin=elastic protein, keeps thin & thick aligned

Acts as the “door,” the strand that covers G actin to prevent binding with myosin

Acts as the “lock,” globular protein on tropomyosin strand, binds with Ca to unlock active sites

The thick filament that binds with actin during muscle contraction. Looks like a “golf club.” has a head that projects toward thin filament (actin) with a tail bound with other myosin molecules in thick filament, points toward M-line, a hinge that lets head pivot at its base=act of contraction.

the connection made when myosin head connects with G actin active sites

Acts as the “key.” binds to receptor on troponin molecule, troponin-tropomyosin complex changes, exposes active site of G actin

thin filaments are sliding toward center of sarcomere (pulled by thick filaments

H-zones & I-bands get smaller (shorter)->Zones of overlap get larger->Z-lines move closer together->Width of A-band remains constant

neuromuscular junction

synaptic terminal

motor end plates

action potential (increase in sodium ions in sarcolemma)

acetylcholine, a neurotransmitter, changes permeability & properties of another cell’s membrane. (causes sodium-ion rush into sarcoplasm)

• action potential arrives • release of ACh • ACh binds at motor end plate • action potential in sarcolemma • repolarize

• expose active site • Form cross-bridges • myosin heads pivot • cross-bridge releases • reactivation of myosin

end of stimulation at neuromuscular junction, runs out of Ca in sarcoplasm, runs out of energy (ATP) to power contraction -> contraction stops, muscle returns to initial length passively

a fixed muscular contraction after death, lasts 15-25 hours, no ATP to release cross-bridges

Latent Period=action potential moves thru sarcolemma causing Ca2+ release Contraction Phase=calcium ions bind, tension builds to peak Relaxation Phase=Ca2+ levels fall, active sites covered, tension falls to resting levels

repeated stimulations IMMEDIATELY AFTER relaxation phase