BackMuscle Tissue Structure and Function - Anatomy & Physiology
Terms in this set (28)
Skeletal muscle, cardiac muscle, and smooth muscle.
Excitability (responsiveness), contractility (ability to shorten), extensibility (stretching), and elasticity (recoil).
Epimysium surrounds the entire muscle, perimysium surrounds muscle fascicles, and endomysium surrounds individual muscle fibers.
A tendon is a bundle of collagen fibers formed by the merging of epimysium, perimysium, and endomysium at muscle ends, attaching muscle to bone.
A muscle fiber is a single muscle cell, multinucleate, formed by fusion of myoblasts, and characterized by striations.
The sarcolemma is the plasma membrane of a muscle fiber that surrounds the sarcoplasm and initiates contraction via action potentials.
T tubules are invaginations of the sarcolemma that transmit action potentials deep into the muscle fiber to trigger contraction.
The SR is a tubular network around myofibrils that stores and releases calcium ions essential for muscle contraction.
Myofibrils are bundles of protein filaments: thin filaments (actin) and thick filaments (myosin) responsible for contraction.
The sarcomere is the smallest functional unit of a muscle fiber, defined from Z line to Z line, where contraction occurs.
The A band contains thick filaments, the M line (center), the H band (thick filaments only), and the zone of overlap (thick and thin filaments).
Thin filaments contain F-actin, nebulin, tropomyosin, and troponin.
Tropomyosin blocks active sites on actin; troponin binds calcium and moves tropomyosin to expose active sites for myosin binding.
Thick filaments are composed of about 300 myosin molecules, each with a tail and two globular heads that bind actin during contraction.
Thin filaments slide toward the center of the sarcomere, H and I bands narrow, zones of overlap widen, and A band width remains constant.
The NMJ is the synapse between a motor neuron and a skeletal muscle fiber where acetylcholine (ACh) is released to initiate contraction.
ACh binds to receptors on the motor end plate, opening Na+ channels, causing depolarization and generating an action potential in the sarcolemma.
It is the process where an action potential travels down T tubules, triggering Ca2+ release from the SR, which binds troponin and initiates contraction.
Active-site exposure, cross-bridge formation, myosin head pivoting (power stroke), cross-bridge detachment, and myosin reactivation.
ATP depletion stops ion pumps, causing Ca2+ buildup in cytosol and fixed muscle contraction (rigor mortis).
Duration of neural stimulus, presence of free Ca2+ in cytosol, and availability of ATP.
Muscle tone is the normal tension and firmness of a muscle at rest, helping stabilize joints and maintain posture.
Isotonic: muscle changes length producing movement; isometric: muscle develops tension without changing length.
Tension depends on sarcomere length and overlap of thick and thin filaments; maximum tension occurs at optimal overlap.
A motor unit consists of a motor neuron and all the muscle fibers it controls, contracting simultaneously.
Wave summation is increased tension from repeated stimuli before relaxation; tetanus is sustained maximal contraction without relaxation.
ATP is generated by direct phosphorylation of ADP by creatine phosphate, anaerobic glycolysis, and aerobic metabolism.
Fast fibers (quick, strong, fatigue fast), slow fibers (slow, fatigue resistant, high mitochondria), and intermediate fibers (mid-sized, moderate fatigue resistance).