Muscle Physiology Flashcards
What are the functions of skeletal muscle?
Movement, posture, moves waste products&nutrients, regulates organ volumes, aids venous return, heat (shivering)
Characteristics of skeletal muscle?
Irritability - can receive and respond to stimuli
Contractility - can respond to stimulus by shortening
Extensibility - can be stretched/lengthened
Elasticity - ability of muscle to return to resting length after being stretched
Structure of skeletal muscle?
Epimysium - creates structure
Perimysiym - around fibre bundles
Endomysium - around individual fibres
What is sarcoplasmic reticulum?
Surrounds myofibril - close to TT’s sarcolemma - stores ca2+ when relaxed, releases it when contracts
What is neuromuscular transmission?
Motor nerve impulse - ACh into synaptic cleft - binds with ach receptor in motor end plate of muscle fibre - sarcolemma depolarisation, AP generation in muscle - propagates along muscle fibre
What is the command chain?
Brain - spinal cord - peripheral nerve - NMJ - sarcolemma - TT system - SR - Ca2 release - crossbridge formation
What is excitation-contraction coupling?
Muscle AP spreads along sarcolemma - Ca2 channels in SR open, Ca2 released - increased sarcoplasmic Ca2 - binds to troponin - actin and myosin bind - contraction
What is the sliding filament mechanism?
Thick and thin filaments slide past each other causing contraction - unbind allows relaxation
Myosin heads bind to actin - actin pulled toward M line - sarcomeres shorten - muscle contracts
What is length-tension relationship?
Forcefulness of contraction depends on sarcomere length & overlap zone - increase overlap = overstretch, decrease overlap = understretch
What are the muscle fibre types?
Slow twitch: type I, slow oxidative, prolonged, continuous muscle activity
Fast twitch: type IIa, fast oxidative-glycolytic
Type IIb, fast glycolysis
Fast twitch = rapid and powerful
What is progressive recruitment?
Graduation of muscle force - small steps to start become larger when increase amount of force required
What is the sarcoplasm?
Contains mitochondria, glycogen, myoglobin, SR - it’s the cytoplasm of striated muscle cells
What is the sarcolemma?
Fine, transparent, tubular sheath covers fibres of skeletal muscle - allows nutrients/gases to pass
What is sarcomere?
Stimulated by electrical charge - structural unit of myofibril in striated muscles
What are myofibrils?
Longitudinal arrangement containing myofilaments