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107 Cards in this Set
- Front
- Back
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
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Acetylcholine
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When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
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voltage-gated calcium channels
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What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
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exocytosis
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The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
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binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate
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How is acetylcholine removed from the synaptic cleft?
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diffusion away from the synaptic cleft
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The action potential on the muscle cell leads to contraction due to the release of calcium ions. where are calcium ions stored in the muscle cell?
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terminal cisternae of the sarcoplasmic reticulum
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What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell?
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arrival of an action potential
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The binding of calcium to which molecule causes the myosin binding sites to be exposed?
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Troponin
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When calcium binds to _____, _____ releases tropomysoin, exposing the myosin binding sites.
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Troponin
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A myosin head binds to which molecule to form a cross bridge?
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actin
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What causes the myosin head to disconnect from actin?
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Binding of ATP
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What energizes the power stroke?
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hydrolysis of ATP
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Excitation - contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process?
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Excitation refers to propagation od action potentials along the sarcolemma
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Excitation of the sarcolemma is coupled or linked to the contraction of a Skeletal muscle fiber. What specific event initiates the contraction?
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Calcium release from the sarcoplasmic reticulum initiates the contraction
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A triad is composed of T tubules and 2 adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected?
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a series of proteins that control calcium release
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What is the name given to the regulary spaced infoldings of the sarcolemma?
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Transverse or T Tubules
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Which of the following is most directly responsible for the coupling of excitation to contraction of Skeletal muscle fibers?
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Calcium ions
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What is the relationship between the number of motor neurons recruited and the number of Skeletal muscle fibers innervated?
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hundreds of Skeletal muscle fibers are innervated by a single motor neuron
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Contraction. of Skeletal muscle is controlled by
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somatic motor neurons
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Skeletal muscle lacks the coarse connective tissue sheaths that are found in smooth muscle?
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false
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Skeletal muscle fibers tend to be shorter than smooth muscle fibers?
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false
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Skeletal muscles have one nucleus, but smooth muscle cells are multi-nucleated?
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false
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Skeletal muscle fibers contain sarcomeres; smooth muscle fibers do not.
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true
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Myasthenia gravis is sometimes treated medically by a treatment that involves
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inhibiting the action of acetylcholinesterase
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Skeletal muscles use creatine phosphate instead of ATP
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false
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Skeletal muscles have t tubules
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true
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Skeletal muscles are multi-nucleated
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true
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Skeletal muscle cells contain myoglobin
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true
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Skeletal muscles cells have glycosomes
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true
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outer most connective tissue sheaths are continuous with what?
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tendon
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Which muscle characteristics describes the ability of a muscle to respond to stimulus?
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excitability
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The response of a motor unit to a single action potential of its motor neuron is called
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a muscle twitch
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Which of the following factors influence the velocity and duration of muscle contraction?
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load placed on the muscle
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The distance between z disc's ____ during muscle contraction?
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decreases
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The sliding filament model of contraction states that
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During contraction, the thin myofilaments slide past the thick myofilaments so that the actin and myosin myofilaments overlap to a greater degree
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a muscle that is lengthening while it prices tension is performing an ______ contraction
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eccentric
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Binding of calcium to calmodulin is a step in excitation - contraction coupling of _____ cells.
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smooth muscle
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What specific neurotransmitter is released from the axonal terminus via exocytosis?
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acetylcholine
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When muscle cells break down glucose to generate ATP under oxygen deficient conditions, they will form
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lactic acid
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The major role of sarcoplasmic reticulum is to regulate
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intracellular levels of Ca2+
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Which type of muscle cannot contract without being stimulated by the nervous system?
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Skeletal
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Which pathway for regenerating ATP provides the majority of the energy used for muscle activity during 30 minute of light to moderate exercise?
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aerobic respiration
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Which event is the most significant in initiating the wave of depolarization?
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diffusion of Na+ into the muscle fiber
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binding of acetylcholine to its receptor open ______ that allow Na+ and K+ to diffuse across the sarcolemma.
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chemically gated ion channels
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Duchenne muscular dystrophy could theoretically be cured if
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none of the above
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The A Band is occupier by the entire length of
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thick myofilaments
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slow oxidative muscle fibers are best suited for
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running a marathon
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The first step toward generating a Skeletal muscle contraction is
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stimulation of the muscle by a nerve ending
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The connective tissue sheaths of Skeletal muscle in order from internal to external are
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endomysium, perimysium, and epimysium
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Which muscle fiber is best suited for endurance activities like jogging?
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slow oxidative fibers
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a fascicle is an organized group of muscle fibers bound by a
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perimysium
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The smallest contractile unit of a muscle fiber is
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The sarcomere
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If both neurons were activated, more muscle fibers would contract than if either neuron alone were active. This mechanism for control of the force of muscle contraction is known as
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recruitment
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The force of a muscle contraction is not affected by
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The amount of atp stored in the muscle cells
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What is a cross bridge cycle?
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cycle in which an energized myosin head binds to actin and performs a power stroke, then binds to atp in order to detach and re - energize
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Thick myofilaments are made of
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myosin
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Which of the following is the smallest structural unit in which the distinctive striated bands characteristic of Skeletal muscle are observed?
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myofibrils
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In bedridden patients recovering from a badly fractured femur, disuse atrophy in the thigh muscles is caused by
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decreased synthesis of muscle proteins and or increased breakdown of muscle proteins
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What event directly triggers the release of neurotransmitter from the synaptic vesicles in the axon terminal?
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diffusion of Ca2+ into the axon terminus
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Which protein inhibits interaction between actin and myosin to prevent Skeletal muscle contraction; and which ions remove the inhibition?
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tropomyosin; calcium ions
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Cross bridge formation between myosin heads and actin molecules is caused by the elevation of calcium ion concentration in the cytosol. During rigor mortis, thus elevation of calcium ion concentration in the cytosol is permanent because
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mitochondria stop producing atp molecules required by the sarcoplasmic reticulum's calcium ion pumps
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Muscle tissue does not
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produce blood cells
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Which of the following is correctly paired?
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Skeletal muscle: voluntary control
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Excitation contraction coupling I codes all except which of the following events?
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release of acetylcholine from axon terminals at the neuromuscular junction
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The dense connective tissue of the epimysium is continous with the _______ that connects the muscle to a bone.
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Tendon
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Marathon Runner
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anaerobic pathway
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Weight Lifting
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aerobic pathway
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25 meter swim
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direct phosphorylation
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Muscle tissue has all of the following properties except
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secretion
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The force of muscle contraction is controlled by multiple motor unit summation or recruitment.
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true
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The muscle cell membrane is called the
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sarcolemma
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The end of the muscle that typically moves when a muscle contracts is called the
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insertion
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Which of the choices below does not secs rive how excess post exercise oxygen consumption restores metabolic conditions?
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increases the level of lactic acid in the muscle
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Once a motor neuron is fired, all the muscle fibers in a muscle contract
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false
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______ stores oxygen in muscle cells.
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myoglobin
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The thin filaments actin contain a polypeptide subunit G actin that bears active sites for myosin attachment.
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true
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Which of the following is the correct sequence of events for muscle contractions?
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motor neuron action potential, neurotransmitter release, muscle cell action potential, release or calcium ions from SR, ATP-driven power stroke, sliding of myofilaments
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Which of the following is not a component of the standard treatment for muscle strain?
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stretching of the muscle
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a contraction in which the muscle does not shorten but its tension increases is called isometric contraction
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true
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During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to
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lactic acid
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cardiac muscle has a limited regenerative capacity
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true
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The sliding filament model of contraction involves
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actin and myosin sliding past each other and partially overlapping
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In an isotonic contraction, the muscle
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changes in length and moves the load
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What is the primary function of eave summation?
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produce smooth, continuous muscle contraction
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excitation contraction coupling directly requires which substances?
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Ca2+
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The oxygen binding protein found in muscle cells is
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myoglobin
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Which of the following is not a connective tissue sheaths that wraps individual muscle fibers?
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a pone u roses
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What muscle cells have the greatest ability to regenerate?
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smooth
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Which is the role of calcium ions in muscle contraction?
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bind to regulatory sites on troponin to remove contraction inhibition
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One of the important functions of Skeletal muscle contraction is production of heat.
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true
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a motor neuron and all the muscle cells that it stimulates are referred to as a motor end plate
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false
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Only _____ muscle cells are always multi-nucleated.
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Skeletal
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What is the role of tropomysoin in Skeletal muscles?
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serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules
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Which of the following would be recruited later In muscle stimulation when contractile strength increases?
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motor units with larger, less excitable neurons
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Muscle contraction will always promote movement of body pars regardless of how they are attached.
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false
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eccentric contractions are more forceful than concentric contractions.
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true
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What does excess post exercise oxygen consumption represent?
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tbe difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used
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The giant protein titin maintains the organization of the ______ assisting in muscle stretching
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band
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Muscle cells store more creative phosphate than atp resulting in the muscle having a reserve source of energy.
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true
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immediately following the arrival of the stimulus at a Skeletal muscle cell there is a short period called the _______ period during which the neurotransmitter is released by exocytosis, diffuses across the synaptic cleft, and binds to its receptor.
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latent
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hypothetically, it a muscle were stretched to the point where thick and thin filaments no longer overlapped
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No muscle tension could be generated
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What structure in Skeletal muscle cells functions in calcium storage?
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sarcoplasmic reticulum
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What is the most distinguishing characteristic of muscle tissue?
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The ability to transform chemical energy into mechanical energy
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What is the role of tropomyosin in Skeletal muscles?
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serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules
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Muscle tone is
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a state of sustained partial contraction
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When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?
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refractory periods
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3 discrete types of muscle fibers are identified on the basis of their size, speed, and endurance. which of the following athletic endeavors best represents the use of red fibers?
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a long relaxing swim
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