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A form of physical exercise, such as running or swimming, that promotes cariopulmonary efficiency and fatigue resistance more than muscular strength. Compare resistance exercise.
Endurance Excercise
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A neurotransmitter released by somatic motor fibers, parasympathetic fibers, and some other neurons, composed of choline and an acetyl group
Acetylcholine
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A muscle contraction in which the muscle shortens and moves a load while its internal tension remains constant
Isotonic contraction
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A stable voltage across the plasma membrane of an unstimulated cell
Resting membrane potential
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In skeletal and cardiac muscle, the portion of a myofibril from one Z disc to the next, constituting one contractile unit
Sarcomere
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An intracellular protein that binds calcium ions and mediates many of the second messenger effects of calcium
Calmodulin
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A microscope that uses an electron beam in place of light to form high-resolution, three-dimensional images of the surfaces of objects; capable of much higher magnification than a light microscope
Scanning electron microscope
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Nonstriated invoulantary muscle found in the walls of the blood vessels, many of the viscera, and other places
Smooth muscle
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A junction at the end of an axon where it stimulates another cell
Synapse
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The tendency of a stretched structure to return to its original dimensions when tension is released
Elasticity
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A rapid voltage change in which a plasma membrane briefly reverses electrical polarity; has a self-propagating effect that produces a traveling wave of excitation in nerve and muscle cells
Action potential
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A motor protein that constitues the thick myofilaments of muscle and has globular, mobile heads of atpase that bind to actin molecules
Myosin
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The smooth endoplasmic reticulum of a muscle cell, serving as a calcium reservoir
Sarcoplasmic reticulum
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The swollen tips of the distal branches of an axon; the site of synaptic vesicles and neurotransmitter release
synaptic knobs
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A protein found in smooth endoplasmic reticulum that reversibly binds and stores calcium ions, rendering calcium chemically unreactive until needed for such processes as muscle contraction
Calsequestrin
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A spheroid organelle in a synaptic knob containing neurotransmitter
Synaptic vesicle
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A tissue composed of elongated, electrically excitable cells specialized for contractio; the three types are skeletal, cardiac, and smooth muscle
Muscular tissue
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A red oxygen-storage pigment of muscle; supplements hemoglobin in providing oxygen for aerobic muscle metabolism
Myoglobin
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A narrow space between the synaptic knob of an axon and the adjacent cell, across which a neurotransmitter diffuses
Synaptic cleft
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The minimum voltage to which the plasma membrane of a nerve or muscle cell must be depolarized before it produces an action potential
Threshold
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A bundle of myofilaments forming an internal subdivision of a cardiac or skeletal muscle cell
Myofibril
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An energy storage molecule in muscle tissue that donates a phosphate group to ADP and thus regenerates ATP in periods of hypoxia
Creatine phosphate
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A catecholamine that functions as a neurotransmitter and adrenal hormone, especially in the sympathetic nervous system
Norepinephrine
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Events that link the synaptic stimulation of a muscle cell to the onset of contraction
Excitation-contraction coupling
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A tubular extension of the plasma membrane of a muscle cell that conducts action potentials into the sarcoplasm and excites the sarcoplasmic reticulum
T tubule
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An enzyme that hydrolyzes acetylcholine, thus halting signal transmission at a cholinergic synapse
Acetylcholinesterase
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The ability of a cell to respond to a stimulus, especially the ability of nerve and muscle cells to produce membrane voltage changes in response to stimuli; irritability
Excitability
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A law that relates the tension generated by muscle contraction to the length of the muscle fiber prior to stimulation; it shows that the greatest tension is generated when the fiber exhibits an intermediate degree of stretch before stimulation
Length-tension relationship
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A diffrence in ion concentration from one point to another, resulting in a gradient of both chemical concentration and electrical charge
Electrochemical gradient
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Having the same osmotic pressure as human cells or some other reference solution
Isotonic
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The interval between a stimulus and response, especially in the action of nerve muscle cells
Latent period
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A muscle contraction in which internal tension rises but the mucsle does not shorten
Isometric Contraction
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A depression in a muscle fiber where it has synaptic contact with a nerve fiber and has a high density of neurotransmitter receptors
Motor end plate
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One motor neuron and all the skeletal muscle fibers innervated by it
Motor unit
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A state of continual, partial contraction of resting skeletal or smooth muscle
Muscle tone
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A protein microfilament responsible for the contraction of a muscle cell, composed mainly of myosin or actin
Myofilament
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A statement pertaining to action potentials and the contraction of muscle fibers that a cell either produces its maximum response or no response at all, depending on whether the stimulus is above or below threshold.
All-or-none law
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A synapse between a nerve fiber and a muscle fiber
Neuromuscular junction
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A wave of constriction traveling along a tubular organ such as the esophagus or ureter, serving to propel its contents
Peristalsis
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A perriod of time after a nerve or musle cell has responded to a stimulus in which it cannot be reexcited by a threshold stimulus
Refractory period
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