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Muscles #1
Muscles #1
32
Anatomy
Undergraduate 1
10/13/2009

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Term
what is the main function of the muscle?
Definition
contraction and shortening
Term
what are muscle fibers?
Definition
skeletal or smooth muscle cells
Term
what is striated muscle?
Definition
skeletal muscle is called this because of the obvious stripes
Term
what is voluntary muscle
Definition
muscle type subject to conscious control (skeletal muscle)
Term
what are skeletal muscles?
Definition
muscles that attach to the body's skeleton
Term
what is the endomysium?
Definition
a delicate connective tissue sheath that encloses each muscle fiber
Term
what is the perimysium?
Definition
a coarse fibrous membrane that wraps the muscle fibers
Term
what is a fascicle?
Definition
a bundle of muscle fibers
Term
what is the epimysium
Definition
an even tougher "overcoat" of connective tissue (covers the entier muscle)
Term
what do the epimysia turn into?
Definition
they blend into the strong, cordlike tendons or into sheetlike aponeuroses
Term
what is a tendon?
Definition
cord or band of inelastic tissue connecting a muscle to bone
Term
what is an aponeuroses?
Definition
sheetlike attachment that binds muscles indirectly to bones, cartilage, or connective tissue coverings
Term
what is smooth muscle?
Definition
this type of muscle has no striations and is involuntary (stomach and bladder)
Term
what is cardiac muscle?
Definition
a type of involuntary striated muscle found solely in the heart
Term
what are intercalated discs?
Definition
these are special junctions that join the branching cells of the cardiac muscle fibers
Term
what are the functions of skeletal muscles?
Definition
they maintain posture, stabilize joints, and generate heat (produce movement)
Term
what are myofibrils?
Definition
long ribbon-like organelles that nearly fill the cytoplasm
Term
what gives muscles their striped appearance?
Definition
the alternating light (I) and dark (A) bands along the length of the perfectly aligned myofibrils
Term
what is a sarcomere?
Definition
chains of tiny contractile units
Term
what are the two types of myofilaments?
Definition
the thin (actin) filaments and the thick (myosin) filaments
Term
what are cross bridges?
Definition
these are when the myosin heads link the thick and thin filaments together during a contraction
Term
what is the sarcoplasmic reticulum?
Definition
a specialized smooth endoplasmic reticulum that surrounds each of the myofibrils
Term
what are the four special functional properties of muscles?
Definition
excitability, contractility, extensibility, and elasticity
Term
what is excitability?
Definition
the ability to receive and respond to a stimulus (responsiveness or irritability)
Term
what is contractility?
Definition
the ability to shorten (forcibly) when adequately stimulated
Term
what is extensibility?
Definition
the ability of muscle cells to be stretched
Term
what is elasticity?
Definition
their ability to recoil and resume their resting length after being stretched
Term
what is a motor unit?
Definition
one neuron and all the skeletal muscle cells it stimulates
Term
what is an axon?
Definition
long, threadlike extensions of the neuron (nerve fiber)
Term
what is the neurotransmitter?
Definition
this chemical is released when a nerve impulse reaches the axon terminals
Term
what is acetylcholine (ACh)?
Definition
the specific neurotransmitter that stimulates skeletal muscle cells
Term
what is the action potential?
Definition
electrical current caused by an "upset" or inbalance of Na+ ions.
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