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the ability of cells or parts of cells to actively generate force to undergo shortening for movements
a dense sheet or broad band of dense irregular connective tissue that lines the body wall and limbs and supports and surrounds muscles and other body organs; holds muscles with similar functions together
connective tissue layer that surrounds groups of 10 to 100 or more muscle fibers, separating them into bundles
a cord of dense regular connective tissue composed of parallel bundles of collagen fibers that attach a muscle to a periosteum of a bone
transverse (T) tubules
tiny, cylindrical invaginations of the sarcolemma of striated muscle fibers that conduct muscle action potentials toward the center of each muscle fiber
red-colored, iron-containing muscle protein that binds oxygen molecules that diffuse into the muscle fiber sarcoplasm from interstitial fluid
threadlike structures that extend longitudinally through a muscle fiber consisting mainly of thick filaments and thin filaments
sarcoplasmic reticulum (SR)
fluid-filled system of membranous sacs that encircle each myofibril; stores and releases calcium ions
a wasting away of muscles because of progressive loss of myofibrils due to disuse or denervation
the thin and thick proteins within myofibrils that are directly involved in the contractile process
the darker middle part of the sarcomere which extends the entire length of the thick filaments
one of two regulatory proteins that is part of the thin filament; covers the myosin-binding sites on actin
one of two regulatory proteins that is part of the thin filament; binds to calciumm ions and undergoes a shape change that moves tropomyosin away from the myosin-binding sites on actin
sliding filament model
the model that describes how skeletal muscle shortens during contraction due to the thin filaments sliding past the thick filaments
a region where communication occurs between two neurons, or between a neuron and a target cell
chemicals that allow the first cell at a synapse to communicate with the second cell
hundreds of membrane-enclosed sacs that are suspended in the cytosol within each synaptic end bulb
the neurotransmitter stored in synaptic vesicles that is released at the neuromuscular junction
an energy-rich molecule found only in muscle fibers that is synthesized when there is excess ATP
aerobic cellular respiration
a series of oxygen-requiring reactions that produce ATP in mitochondria
oxygen debt (recovery oxygen uptake)
refers to the added oxygen, over and above the resting oxygen consumption, that is taken into the body after exercise
the brief delay that occurs between application of the stimulus and the beginning of contraction; the muscle action potential sweeps over the sarcolemma and calcium ions are released from the sarcoplasmic reticulum
during this time, calcium ions bind to troponin, myosin-binding sites on actin are exposed, and crossbridges form
during this time, calcium ions are actively transported back into the sarcoplasmic reticulum, myosin-binding sites are covered by tropomyosin, myosin heads detach from actin, and tension in the muscle fiber decreases
the time when a muscle fiber receives enough stimulation to contract that it temporarily loses its excitability and cannot respond for a time
a small amount of tautness or tension in the muscle due to weak, involuntary contractions of its motor units
the tension (force of contraction) developed by the muscle remains almost constant while the muscle changes its length; used for body movements and for moving objects
occurs when the tension generated is not enough to exceed the resistance of the object to be moved, and the muscle does not change its length; holding a book steady using an outstretched arm
slow oxidative (SO) fibers
muscle fibers that are the smallest in diameter, the least powerful, appearing dark red due to large amounts of myoglobin and many blood capillaries; fatigue-resistant fibers that are adapted for maintaining posture and for aerobic, endurance-type activities like running a marathon
fast oxidative-glycolytic (FOG) fibers
muscle fibers that are intermediate in diameter, appearing dark red due to large amounts of myoglobin and many blood capillaries; used in walking and sprinting
fast glycolytic (FG) fibers
muscle fibers that are the largest in diameter and contain the most myofibrils; able to generate the most powerful contractions; low myoglobin content and few blood capillaries; adapted for intense anaerobic movements of short duration such as weight lifting
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