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What is the role of tropomyosin in skeletal muscles?
A. tropomyosin is the chemical that activates the myosin heads
B. tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on actin molecules
C. tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules
D. tropomyosin is the receptor for the motor neuron neurotransmitter
Which muscle cells have the greatest ability to regenerate?
D. no muscle can regenerate
Most skeletal muscles contain ______.
A. muscle fibers of the same type
B. a mixture of fiber types
C. a predominance of slow oxidative fibers
D. a predominance of fast oxidative fibers
Fatigued muscle cells that recover raidly are the products of ________.
A. intense exercise of long duration
B. intense exercise of short duration
C. slow exercise of long duration
D. slow exercise of short duration
The strongest muscle contractions are normally achieved by ________.
A. increasing stimulus above the threshold
B. increasing stimulus above the treppe stimulus
C. increasing the stimulation up to the maximal stimulus
D. recruiting small and medium muscle fibers
Which of the following would be recruited later in uslce stimulation when contractile strength increases?
A. motor units with the longest muscle fibers
B. many small motor units with the ability to stimulate other motor units
C. large motor units with small, highly excitable neurons
D> motor units with larger, less excitable neurons
Excitation-contraction coupling requires which of the following substances?
A. Ca2+ and ATP
B. Ca2+ only
C. ATP only
D. ATP glucose
Which of the following is a factor that affects the velocity and duration of muscle contraction?
A. number of muscle fibers stimulated
B. size of the muscle fibers stimulated
C. load on the fiber
D. muslce length
A. breaks down the glycogen
B. is a protein involved in the direct phosphorylation of ADP
C. stores oxygen in muscle cells
D. produces the end plate potential
What structure in skeletal muscle cells functions in calcium storge?
A. sarcoplasmic reticulum
C. intermediate filament network
D. myofibrillar network
What does excess postexercise oxygen consumption represent?
A. amount of oxygen needed for aerobic activity to accomplish the same amount of work
B. the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used
C. the amount of oxygen equal to the oxygen already used
D. the amount of oxygen taken into the body immediately after the exertion
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 synatic cleft, and binds to its receptors.
Creatine phosphate functins in the muscle cell by _______.
A. forming a temporary chemical compund with myosin
B. forming a chemical comound with actin
C. inducing a conformational change in the myofilaments
D. storing energy that will be transferred to ADP to resynthesize ATP
What is the primary function of wave summation?
A. produce smooth, continuous muscle contraction
B. increase muscle tension
C. revent muscle relaxation
D. prevent muscle fatigue
The major function of the sarcoplasmic reticulum in muscle contraction is to _______.
A. make and store phospocreatine
B. synthesize actin and myosin myofilaments
C. provide a source of myosin for the contraction process
D. regulate intrcellular calcium concentration
What produces the striations of a skeletal muscle cell?
A. a difference in the thickness of the sarcolemma
B. the arrangement of myofilaments
C. the sarcoplasmic reticulum
D. the T tubules
During muscle contraction, myosin cross bridges attach to which active sites?
A. myosin filaments
B. actin filaments
C. Z discs
D. thick filaments
Which of the following surrounds the individual muscle cell?
Rigor mortis occurs because ______.
A. the cells are dead
B. sodium ions leak into the muscle causing continued contractions
C. no ATP is available to release attached actin and myosin molecules
D. proteins are beginning to break down, thus preventing a flow of calcium ions
Which of the choices below does not describe how excess postexercise oxygen consumption (oxygen deficit) restores metabolic conditions?
A. converts lactic acid back into glycogen stores in the liver
B. resynthesizes creatine phosphate and ATP in muscle fibers
C. increases the level of lactic acid in the muscle
D. replaces the oxygen removed from myoglobin
The term aponeurosis refers to _____.
A. the bands of myofibrils
B. a sheetlike indirect attachment to a skeletal element
C. the rough endoplasmic reticulum
D. the tropomyosin-troponin complex
The oxygen-binding protein found in muscle cells is _______.
The contractile units of skeletal muscles are ______.
C. T tubules
What is the functional unit of a skeletal muscle called?
A. a sarcomere
B. a myofilament
C. a myofibril
D. the sarcoplasmic reticulum
What is the functional role of the T tubules?
A. stabilizw the G and F actin
B. enhance cellular communication during muscle contraction
C. hold cross bridges in place in a resting muscle
D. synthesize ATP to provide energy for muscle contraction
What is the role of calcium ions in muscle contraction?
A. form hydroxyapatite crystals
B. reestablish glycogen stores
C. bind to regulatory sites on troponin to remove contraction inhibition
D. increase levels of myoglobin
Which of the following is not a component of the standard treatment for muscle strain?
A. rest of the muscle
B. ice on the muscle
C. elevation of the limb
D. stretching of the muscle
Which of the following is not a connective tissue sheath that wraps individual muscle fibers?
During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a resule, the pyruvic acid is converted to_______.
A. a strong base
B. stearic acid
C. hydrochloric acid
D. lactic acid
When a muscle is unable to respond to stimuli temporarily, it is in which of the following periods?
A. relaxation period
B. refractory period
C. latent period
D. fatigue period
In an isotonic contraction, the muscle ______.
A. changes in length and moves the "load"
B. does not change in length but increases tension
C. never converts pyruvate to lactate
D. rapidly resynthesizes creatine phosphate and ATP
The muscle cell membrane is called the _______.
Which of the following is the correct sequence of events for muscle contraction?
A. motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke sliding of myofilaments
B. neurotransmitter release, muscle cell action potentioal, moter neuron action potential, release of calcium ions from SR, sliding of myofilaments, ATP-driven power stroke
C. muscle cell action potential, neurotransmitter release, ATP-driven power stroke, calcium ion release from SR, sliding of myofilaments
D. neurotransmitter release, moto neuron action potential, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke
The mechanism of contraction in smooth muscle is different from skeletal muscle in that ________.
A. actin and myosin interact by the sliding filament mechanism
B. the triger for contraction is a rise in intracellular calcium
C. the site of calcium regulation differs
D. ATP energizes the sliding process
Which of the following describes the cells of unitary smooth muscle?
A. they depend upon recruitment using the autonomic nervous system
B. they are used for vision and hair raising
C. they exhibit spontaneous action potentials
D. they consist of muscle fibers that are structurally independent of each other
Which of the following is not a role of ionic calcium in muscle contraction?
A. triggers neurotransmitters secretion
B. binds with troponin
C. removes contraction inhibitor
D. activates epinephrine released from adrenal gland
Which of the following is true about smooth muscle?
A. certain smooth muscle cells can actually divide to increase their numbers
B. smooth muscles, in contrast to skeletal muscle, cannot synthesize or secrete any connective tissue elements
C. smooth muscle cannot stretch as much as skeletal muscle
D. smooth muscle has well-developed T tubules at the site of invagination
Smooth muscle is characterized by all of the following except __________.
A. it appears to lack troponin
B. there are more thick filaments than thin filaments
C. there are no sarcomeres
D. there are noncontractile intermediate filaments that attach to dense boies within the cell
Muscle tissue has all of the following properties except ______.
The giant protein titn maintains the organization of the ___________ assisting in muscle stretching.
A. A band
B. I band
C. Z disc
D. M line
Which of the following statements is true?
A. Cardiac muscle cells have many nuclei
B. smooth muscle cells have T tubules
C. striated muscle cells are long and cylindrical with many nuclei
D. cardiac muscle cells are found in the heart and lare blood vessels
An anaerobic pathway that results in the prouction of two net ATP's per glucose plus two pyruvic acid molecules is _________.
A. the citric acid cycle
D. the electron transport chain
Muscle tone is _______.
A. the ability of a muscle to efficiently cause skeletal movements
B. the feeling of well-being following exercise
C. a state of sustained partial contraction
D. the condition of athletes after intensive training
The sliding filament model of contraction involves _______.
A. actin and myosin sliding past each other and partially overlapping
B. the shortening of thick filaments so that thin filaments slide past
C. actin and myosin lengthening in order to slide pase each other
D. the Z discs sliding over the myofilaments
After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction?
A. calcium ions returning to the terminal cisternae
B. the tropomyosin blocking the myosin once full contraction is achieved
C. acetylcholinesterase destroying the ACh
D. the action potential stops oing down the overloaded T tubules
Which of the following statements is most accurate?
A. muscle tension remains relatively constatnt during isotonic contraction
B. T tubules may be sliding during isotonic contraction
C. the I band lengthens during isotonic contraction
D. myofilaments slide during isometric contractions
What is the most distinguishing characteristic of muscle tissue?
A. the design of fibers
B. the ability to respond to nervous stimulation
C. the diversity of activity of muscle tissue
D. ability to transform chemical energy into mechnical energy
the ability to transform chemical energy into mechanical energy
Three 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?
A. a sprint by an Olympic runner
B. a long, relaxing swim
C. playing baseball or basketball
D. gym climbing
Of the following muscle types, which has only one nucleus, no sarcomeres, and rare gap junctions?
A. visceral smooth muscle
B. multiunit smooth muscle
C. cardiac muscle
D. skeletal muscle
Hypothetically, if a muscle were stretched to the point where thick an thin filaments no longer overlapped, ________.
A. cross bridge attachment would be optimum because of all the free binding sites on actin
B. no muscle tension could be generated
C. maximum force production would result because the muscle has a maximum range of travel
D, ATP consumption would increase because the sarcomere is "trying" to contract
What part of the sarcolemma contains acetylcholine receptors?
A. motor end plate
B. end of the muscle fiber
C. part adjacent to another muscle cell
D. any part of the sarcolemma
Which of the following statements is false or incorrect?
A. cardiac muscle contracts when stimulated by its own autorhythmic muscle cells
B. under normal resting conditions, cardiac muscle tissue contracts and reflexes about 75 times per minute
C. cardiac muscle fibers depend mostly on anaerobic cellular respiration to generate ATP
D. cardiac muscle fibers can use lactic acid to make ATP
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