BackAnatomy & Physiology Exam 3 Review: Muscle Tissue and Skeletal Muscles
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Terms in this set (27)
The three muscle types are skeletal (voluntary, striated, multinucleated), cardiac (involuntary, striated, branched, with intercalated discs), and smooth (involuntary, non-striated, spindle-shaped cells).
Excitability, contractility, extensibility, and elasticity.
The sarcomere is the basic contractile unit of a muscle fiber, composed of overlapping thick (myosin) and thin (actin) filaments between two Z discs.
It explains muscle contraction as the thin actin filaments sliding past thick myosin filaments, shortening the sarcomere without changing filament length.
The SR stores calcium ions and releases them to trigger contraction; T tubules transmit action potentials deep into the muscle fiber to stimulate the SR.
A motor unit consists of a single motor neuron and all the muscle fibers it innervates, coordinating contraction.
The neuromuscular junction is the synapse where a motor neuron communicates with a muscle fiber to initiate contraction.
ACh is a neurotransmitter released at the neuromuscular junction that binds to receptors on the muscle fiber, triggering an action potential.
An action potential is an electrical signal generated by depolarization of the sarcolemma, leading to muscle contraction.
Depolarization is the influx of Na+ ions making the membrane potential more positive; repolarization restores the resting negative membrane potential by K+ efflux.
It is the process where an action potential triggers calcium release from the SR, enabling the sliding filament mechanism and muscle contraction.
Calcium binds to troponin, causing tropomyosin to move and expose binding sites on actin for myosin, allowing contraction.
Concentric contractions shorten the muscle (lifting), while eccentric contractions lengthen the muscle under tension (lowering).
A muscle twitch is a single, brief contraction and relaxation cycle in a muscle fiber following a stimulus.
Variations in muscle contraction strength due to changes in stimulus frequency (e.g., tetanus) or stimulus strength (recruitment).
Direct phosphorylation (creatine phosphate), anaerobic glycolysis, and aerobic respiration, used depending on activity duration and intensity.
Muscle contractions produce heat as a byproduct, helping maintain body temperature.
Smooth muscle uses calmodulin instead of troponin, contracts slower, and can sustain contractions longer with less energy.
Gap junctions are channels that allow electrical signals to pass directly between cardiac or smooth muscle cells for coordinated contraction.
Muscle tone is the continuous, passive partial contraction of muscles to maintain posture and readiness.
Sarcopenia is the age-related loss of muscle mass and strength.
The diaphragm is the primary muscle of inspiration, contracting to increase thoracic volume and draw air into the lungs.
Origin is the fixed attachment point; insertion is the movable attachment where force is applied.
Muscles are named based on location, shape, size, direction of fibers, number of origins, or action (e.g., biceps = two heads).
A fascicle is a bundle of muscle fibers surrounded by connective tissue.
Varicosities are swellings along autonomic nerve fibers that release neurotransmitters to smooth muscle cells.
It is the ability of smooth muscle to stretch and then relax to accommodate volume changes without contracting.