Muscle Physiology

• The types of muscles are skeletal, cardiac, and smooth
• Skeletal muscle is attached to bones by tendons, has striations and is voluntary.
• Smooth muscle is found in walls of hollow organs, blood vessels, and glands; has single nucleus, no striations, and is involuntary
• Cardiac muscle is found in the heart, has striations, and is involuntary
• Muscle (organ) is surrounded by epimysium, which is connected to fascia between muscles
• Fasciculus are bundles of muscle cells/fibers surrounded by perimysium
• Endomysium surrounds individual muscle fibers
• Actin and Myosin are myofilaments that compose myofibrils arranged in sarcomeres
• Actin are thin myofilaments
• Myosin are thick myofilaments
• Sarcolemma is the cell membrane of a muscle fiber
• Sarcoplasm is the cytoplasm of a muscle fiber
• Sacroplasmic reticulum is the "endoplasmic reticulum" for a muscle fiber that releases calcium
• Transverse tubules are networks of tubes that connect sarcolemma to sacroplasmic reticulum (transport)
• Resting membrane potential describes the difference in electrical charge across a cell membrane
• The outside of a cell is more positive, while the inside is more negative
• Action potential is when there's an influx of sodium into the cell which causes depolarization
• Depolarization is when the sodium and potassium channels open, and "switching" the inside of a cell from negative to positive and vice versa for the outside.
• Repolarization is when the sodium and potassium channels close, and the sodium/potassium pump begins to pump out ions again until the membrane is back to how it was before the action potential
• Motor neurons to innervate all muscle tissue
• Presynaptic terminals are the ends of motor neurons/axons
• Synaptic vesicles store neurotransmitters (acetylcholine) and release them into the synaptic cleft
• Acetylcholine binds onto receptor sites on the sodium channel, which sends a signal to open them
• Calcium is released after acetylcholine binds to the sodium channel, and triggers "sliding filament"
• Acetylcholinesterase (enzyme) degrades remaining acetylcholine to limit contraction stimulus
• Sliding filament is when actin and myosin bind onto each other, causing sarcomeres to shorten.
• Troponin and Tropomyosin act a "body guards" from preventing actin to bind onto myosin. However, calcium can bind onto troponin and pull tropomyosin away from the active site.
• The only myosin heads that can bind onto active sites are those that already had ATP broken down into ADP + Pi. The energy stored from ADP + Pi allows the myosin head to latch onto actin.
• When actin and myosin finally bind, there is no use for ADP + Pi so they unbind which changes the shape and a new ATP binds onto where ADP + Pi once was, releasing myosin from actin.
• Muscle twitch is a contraction of a muscle fiber in response to a stimulus
• Lag phase is time between stimulus application and the start of contraction
• Contraction phase is the time of contraction
• Relaxation phase is the time of relaxation
• Summation is increasing the force of muscle fibers
• Recruitment is increasing number of muscle fibers contracting within muscles
• Tetanus is sustained muscular contraction where there is no relaxation and instead pushing oneself
• Mitochondria produce ATP
• Anaerobic respiration is without oxygen
• Aerobic respiration is with oxygen
• Anaerobic generates 2 ATP with lactic acid as a waste product