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Anatomy and Physiology I
Chapter 9 Vocab
32
Science
Undergraduate 2
07/19/2009

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Term
Muscle Fiber
Definition
Skeletal and smooth muscle cells. Are elongated.
Term
Excitability
Definition
The ability to recieve and respond to a stimulus.
Term
Contractility
Definition
The ability to shorten forcibly when adequately stimulated.
Term
Extensibility
Definition
The ability to be stretched or extended.
Term
Elasticity
Definition
The ability of a muscle fiber to recoil and resume its resting length after being stretched.
Term
Endomysium
Definition
A fine sheath of connective tissue consisting of areolar and reticular fibers that surrounds each individual muscle fiber.
Term
Fascicles
Definition
Bundles of endomysium-wrapped muscle fibers.
Term
Perimysium
Definition
A layer of fibrous connective tissue that surrounds each fascicle.
Term
Epimysium
Definition
An overcoat of dense irregular connective tissue that surrounds the whole muscle.
Term
Myoglobin
Definition
A red pigment that stores oxygen and is simular to hemoglobin.
Term
Myofibrils
Definition
Each muscle contains many rodlike myofibrils that run parallel to its length.
Term
Thick Filament
Definition
Type of myofilament. Extend the entire length of the A band.
Term
Thin Filament
Definition
Type of myofilament. Extends across the I band and partway into the A band.
Term
Cross Bridges
Definition
Where the thick and thin filaments link toegther. Also known as the globular heads of a myosin molecule.
Term
Tropomyosin
Definition
A rod-shaped protein that spirals about the actin core and helps to stiffen it.
Term
Troponin
Definition
A three-polypeptide complex. One of the polypeptides binds to actin, another binds to tropomyosin, and the third  binds calcium ions.
Term
Neuromuscular Junction
Definition
Region where a motor neuron comes into close contact with a skeletal muscle cell.
Term
Synaptic Cleft
Definition
The space that separates the axon terminal and the muscle fiber. It is filled with a gel-like extracellular substance rich in glycoproteins and collagen fibers.
Term
Motor End Plate
Definition
The troughlike part of the muscle fiber's ssarcolemma that helps form the neuromuscular junction.
Term
Depolarization
Definition
Loss of a state of polarity; loss or reduction of negative membrane potential.
Term
Repolarization
Definition
The restoration of polarity.
Term
Refractory Period
Definition
During repolarization a muscle fiber is said to be in a refractory period because the cell cannot be stimulated again until repolarization is complete.
Term
Latent Period
Definition
Stage of the muscle twitch. The first few miliseconds following stimulation when excitation-contraction coupling is occuring. During this period muscle tension is beginning to increase but no response is seen on the myogram.
Term
Period of Contraction
Definition
Stage of the muscle twitch. The period when cross bridges are active and the myogram tracing rises to a peak.
Term
Period of Relaxtion
Definition
Stage of the muscle twitch. The period  that is initiated by reentry of calcium into the SR. Muscle tension decreases to zero and the tracing returns to the baseline.
Term
Fused Tetanus
Definition
At this point all evidence of muscle relaxation disappears and the contractions fuse into a smooth, sustained contraction plateau.
Term
Muscle Tone
Definition
The phenomenon where even relaxed muscles are always slightly contracted.
Term
Creatine Phosphate
Definition
A unique high-energy molecule stored in muscles. It is tapped to regenerate ATP while the metabolic pathways are adjusting to the suddenly higher demands for ATP.
Term
Aerobic Respiration
Definition
Occurs in the mitochondria. It requires oxygen and involves a sequence of chemical reactions in which the bonds of fuel molecules are broken and the energy released is used to make ATP.
Term
Anaerobic Glycolysis
Definition
Energy-yielding conversion of glucose to lactic acid in various tissues, notably muscle, when sufficient oxygen is not available.
Term
Muscle Fatigue
Definition
A state of physiological inability to contract even though the muscle still may be recieving stimuli.
Term
Contractures
Definition
States of continuous contraction because the cross bridges are unable to detatch.
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