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The type of muscle found in the walls of the digestive tract is
smooth muscle
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Heart muscle is also known as
cardiac muscle
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The most abundant type of muscle in the body is a striated muscle, also known as
skeletal muscle
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Muscles that work against each other are said to be
antagonists
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The submicroscopic filaments of a muscle cell are known as
myofibrils
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The functional unit of muscle activity is known as the
sarcomere
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The thick filaments in the central protion of hte sarcomere are composed of the protein
myosin
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The thin filaments of a sarcomere are composed of the protein
actine
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The thin filaments of the sarcomere in a skeletal muscle fiber are anchored to the
z-line
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The theory explaining the contraction of muscle fibers is called the
sliding filament theory
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During muscle contractions, the thick filaments pull on the thin filaments attached to the Z lines and shorten the
sarcomere
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The primary source of energy for muscle contraction is
ATP
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Red muscle has oxygen stored in a red-pigmented molicule called
myoglobin
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The continual contractions of muscle fibers require a supply of hte energy molecule
ATP
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White muscle is so-named because it has little or no
myoglobin
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White muscle is not able to store much
oxygen
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White muscle uses stored glycogen for energy, and it is sometimes called
glycolytic muscle
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When a muscle is at rest, myosin heads are prevented from binding to actin by a protein called
tropomyosin
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Muscles are triggered to contract following release of the neurotransmitter
acetylcholine
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The first ion utilized during muscle contraction is
sodium
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Calcium ions are stored in muscle cells within infoldings of hte plasma membrane called
transverse tubules
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Following their release, calcium ions trigger muscle contractions by binding to the molecule
troponin
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The binding of calcium to troponin causes a shift in the molecule
tropomyosin
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The shift of position of tropomyosin unmasks the sites on actin filaments that bind to the heads of
myosin
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Muscle contractions come to an end when tropomyosin covers the myosin-binding sites on
actin
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Energy is used during muscle relaxation to move calcium ions into the sarcoplasmic reticulum and the
T-tubules
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The state of continual muscle contraction following death is called
rigor mortis
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Muscle contracts after its threshold has been reached, and the response is called the
all-or-none response
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The variable response displayed by an entire muscle is known as the
graded response
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The number of muscle fibers contracting in a muscle depends on the stimulation from
nerve impulses
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The contraction of a muscle fiber is known as a
twitch
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All the muscle fibers stimulated by one motor neuron constitute a
motor unit
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The increasing number of twitches occurring with continued muscle stimulation is described as a
summation
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A state of sustained maximum contraction of a muscle is a phenomenon called
tetanus
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The condition in which a muscle is kept partially contracted over a long period of time is known as
tonus
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When ATP is broken down in muscle cells, the two end products are phosphate groups and
ADP
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One source for regenerating ATP is the high-energy molecule
creatine phosphate
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in order for the most energy to be released from carbohydrate molecules in muscle cell metabolism, an essential gas is
oxygen
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when muscle is oxygen-depleted, the energy for muscle contraction is derived from an anaerobic process called
glycosis
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Extreme muscle fatigue is generally due to the buildup of an acid called
lactic acid
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following strnuous activity, a person breathes deeply to repay an
oxygen debt
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much of the lactic acid produced during strenous activity is carried from the muscle cells for metabolism by the
liver
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where contractions of the skeletal muscles are fast, the contractions of smooth muscles are generally
slow
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smooth muscle is so-named because it contains no
striations
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the muscle cells between some smooth muscles are linked together by junctions known as
gap junctions
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where skeletal muscles are voluntary muscles, the smooth muscles are
involuntary
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single-unit smooth muscle cells are interconnected by
gap junctions
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cardiac muscle is striated, and it is liberally supplied by energy-yielding organelles called
mitochondria
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the ends of cardiac muscle cells are connected to one another by gap junctions in
intercalated disks
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cardiac muscle is similar to smooth muscle because it is not under
voluntary control
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smooth muscle may be found in the
digestive tract
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the only location for cardiac muscle in the human body is in the
heart
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for every muscle that acts in one direction there is another muscle that is
antagonist
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the skeletal muscles of the body are under
voluntary control
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the two proteins of the myofibrils are
actin and myosin
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