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The thin filaments (actin) contain a polypeptide subunit G actin that bear active sites formyosin attachment
A motor neuron and all the muscle cells that it stimulates are referred to as a motor endplate
A contraction in which the muscle does
not shorten but its tension increases is called isometric
What is the role of tropomyosin in skeletal muscles?
A) Tropomyosin is the name of a contracting unit.
B) Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the 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.
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
Excitation-contraction coupling requires which of the following substances?
A) Ca2+ and ATP
B) Ca2+ only
C) ATP only
D) ATP and glucose
A) breaks down 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 storage?
A) sarcoplasmic reticulum
C) intermediate filament network
D) myofibrillar network
What does oxygen deficit represent?
A) amount of energy needed for exertion
B) the difference between the amount of oxygen needed for totally aerobic muscle activity and the amount actually used
C) the amount of oxygen taken into the body prior to the exertion
D) the amount of oxygen taken into the body immediately after the exertion
Creatine phosphate functions in the muscle cell by ________.
A) forming a temporary chemical compound with myosin
B) forming a chemical compound with actin
C) inducing a conformational change in the myofilaments
D) storing energy that will be transferred to ADP to resynthesize ATP
The major function of the sarcoplasmic reticulum in muscle contraction is to ________.
A) make and store phosphocreatine
B) synthesize actin and myosin myofilaments
C) provide a source of myosin for the contraction process
D) regulate intracellular 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
Which of the following are composed of myosin?
A) thick filaments
B) thin filaments
C) all myofilaments
D) Z discs
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 out of the muscle
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 recovery oxygen uptake (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 contractile units of skeletal muscles are ________.
C) T tubules
One functional unit of a skeletal muscle is ________.
A) a sarcomere
B) a myofilament
C) a myofibril
D) the sarcoplasmic reticulum
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
The main effect of the warm-up period of athletes, as the muscle contractions increase instrength, is to ________.
A) increase the myoglobin content
B) convert glycogen to glucose
C) tone the muscles and stabilize the joints for the workout
D) enhance the availability of calcium and the efficiency of enzyme systems
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
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