CHAPTER 9

25 July 2022
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Functions of muscles include.
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Heartbeat muscle tone moving bones
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The outermost layer of connective tissue surrounding a skeletal muscle is
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epimysium.
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Myofibrils are composed primarily of
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actin and myosin
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The striated appearance of skeletal muscle fibers results from the
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sarcomere organization.
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A sarcomere is best described as
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a unit within a muscle fiber.
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Transverse tubules
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transmit muscle impulses into the cell interior.
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The discoloration and swelling of a muscle strain is due to
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ruptured blood vessels.
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A tendon is ______, whereas an aponeurosis is ______.
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cordlike and connects muscles to bones; a broad sheet of dense connective tissue that connects muscles to
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Muscle fibers are basically a collection of
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sarcomeres.
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Transverse tubules and sarcoplasmic reticulum are well developed in
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skeletal and cardiac muscle fibers
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The functional unit of muscle contraction is
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the sarcomere.
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Neurotransmitters are stored in vesicles in
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motor neuron endings.
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The enzyme acetylecholinesterase causes acetylcholine to
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decompose.
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Creatine phosphate
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supplies energy for the synthesis of ATP.
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The amount of oxygen liver cells require to support the conversion of lactic acid to produce glucose or glycogen is the
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oxygen debt.
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Tawanda finishes a sprint and suffers great pain in her calf muscles. Her muscle cramps are likely due to a temporary deficit of
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ATP.
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Binding sites on the surface of actin allow the formation of cross-bridges with molecules of
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myosin.
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Athletes usually experience muscle fatigue less quickly than nonathletes because they
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produce less lactic acid.
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At a neuromuscular junction, the muscle fiber membrane folds, forming a
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motor end plate.
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The toxin that causes botulism
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prevents release of acetylcholine.
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Rigor mortis affects skeletal muscles a few hours after death, due to
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a decrease in ATP and increased permeability to calcium.
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At a neuromuscular junction
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neurotransmitters are released.
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The first event in muscle fiber contraction is that
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acetylcholine is released from the end of the motor neuron
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Which of the following statements is correct?
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Actin filaments slide along myosin filaments.
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The functional connection between a neuron and a skeletal muscle fiber is a
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synapse.
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_________ degrades acetylcholine, keeping it from accumulating in the synapse.
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Acetylcholinesterase
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Arrange the following steps of muscle fiber contraction in the correct sequence. 1. The muscle impulse reaches the sarcoplasmic reticulum and calcium is released. 2. Thin filaments are pulled over the thick filaments. 3. Calcium floods the sarcoplasm and binds to troponin molecules leaving active sites. 4. The impulse arrives at the synapse and travels through the transverse tubules. 5. The muscle fiber shortens and contracts. 6. Myosin heads bind to exposed active sites on actin, forming cross-bridges.
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4, 1, 3, 6, 2, 5
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A shift in metabolism that breaks down pyruvic acid to lactic acid is called
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lactic acid threshold.
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Oxygen debt in muscles may develop because of
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the inability of respiratory and circulatory systems to supply enough oxygen to skeletal muscles when used strenuously for a minute or two.
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When ATP levels are low, the relationship between ATP and creatine phosphate is that
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creatine phosphate supplies energy to regenerate ATP from ADP and phosphate
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The characteristic reddish brown color of skeletal muscle comes from which substance?
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Myoglobin
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A motor unit is
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a motor neuron and the muscle fibers connected to it
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During muscle contraction ATP supplies energy for
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myofilament movement.
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Skeletal muscles help maintain body temperature in that
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the more active they are, the more heat is released.
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Threshold stimulus is the
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minimum strength of stimulation required to contract a muscle fiber.
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A myogram is
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a recording of the events of a twitch
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A plank position is part of a yoga/Pilates workout. The person supports the body on the floor in a prone position with the arms and feet supporting the body. It is a little like the "up" position of a push-up, held for 30 to 60 seconds. Contraction of the abdominal muscles in a plank is most likely
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isometric.
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An example of a partial but sustained contraction is
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muscle tone.
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Which of the following is not true?
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Red fibers have fewer mitochondria than white
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The increase in the number of motor units activated as a result of more intense stimulation is called
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recruitment.
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In a recording of a muscle twitch, the delay between the time a stimulus is applied and the time the muscle responds is called
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latent period.
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A muscle fiber exposed to a series of stimuli of increasing frequency combines individual twitches (summation) which results in
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complete sustained contraction.
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Activities such as distance swimming and distance running are most likely to stimulate development of
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slow fatigue-resistant fibers.
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Smooth muscle lacks
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transverse tubules and striations.
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Smooth muscle has ___________ and not troponin.
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calmodulin
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When a muscle undergoes atrophy in response to disuse
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there is a reduction in capillary networks the size of actin and myosin filaments decreases the muscle gets smaller
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Compared to skeletal muscle, smooth muscle
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contracts more slowly and relaxes more slowly.
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The type of muscle cell that lacks transverse tubules, has a single nucleus, and is under involuntary control is
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smooth muscle.
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Short muscle cells with centrally located nuclei are
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smooth muscle fibers.
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Both acetylcholine and norepinephrine can affect
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smooth muscle contraction.
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The structures that connect cardiac muscle cells are
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intercalated discs.
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Cardiac muscle
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contracts as a syncytium. excites itself is only in the heart
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Bones and muscles function as mechanical devices called
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levers.
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The more movable end of a muscle is its
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insertion.
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The muscle that causes an action is the
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agonist.
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A muscle that assists the agonist is a(n)
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synergist.
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The buccinator muscle is in the
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cheek.
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The muscle that adducts and flexes the arm is the
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coracobrachialis.
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The muscle that opposes a particular action is called the
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antagonist.
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The linea alba is
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a band of tough connective tissue to which abdominal wall muscles
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The soleus is a muscle that forms part of the
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calf.
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Which of the following is not a muscle of mastication?
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Zygomaticus
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Which of the following is unique in that its insertion is to fascia and not bone?
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palmaris longus
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The triangle of auscultation, commonly used to hear sounds of respiratory organs, is located near the border of the
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trapezius and latissimus dorsi.
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A gluteal gait, in which a person walks with a waddling limp, is usually caused by a disorder of the
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gluteus medius and gluteus minimus
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A sign of aging of the muscular system is
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decreased supplies of myoglobin to muscles.
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Regina began an exercise program six months ago, and the muscles of her upper limbs and lower limbs are more prominent. Exercise can lead to formation of new muscle by
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stimulating skeletal muscle cells to release IL-6, which stimulates satellite cells to divide, producing more muscle cells.
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Muscle atrophy that progresses with aging is caused by reduction in
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ATP MYOGLOBIN THE SIZES OF MUSCLE FIBERS
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People with myasthenia gravis have a deficiency of
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acetylcholine receptors
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Myasthenia gravis is
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an autoimmune disorder.
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A weightlifter uses muscles so the muscles exert more than 75% of their maximum tension, this stimulates
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muscle fibers developing new filaments of actin and myosin.
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Fibers of muscles whose motor neurons are severed
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may be replaced by fat or fibrous connective tissue
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Temporomandibular joint (TMJ) syndrome causes
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headache. ringing in the ears clicking sound from the jaw
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Endomysium separates individual muscle fibers from each other.
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TRUE
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A motor neuron and the muscle fibers that it controls constitute a motor unit.
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TRUE
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In the initiation of muscle fiber contraction calcium ions bind to tropomyosin, exposing active sites on actin for cross-bridge formation.
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FALSE
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The enzyme ATPase occurs in the globular portion of myosin molecules.
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TRUE
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Acetylcholine released by the myofibril crosses the synaptic cleft to bind to the motor neuron ending.
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FALSE
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ATP is necessary for muscle relaxation.
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TRUE