Which of the following statements is TRUE regarding skeletal-muscle contraction?
A. Only one cross-bridge cycle can occur when the [Ca2+] is elevated in the cytosol; in order to undergo a second cycle, [Ca2+] must be sequestered in the sarcoplasmic reticulum and released again.
B. ATP hydrolysis products must be removed from myosin before it can bind to actin.
C. Binding of myosin to actin takes place when [Ca2+] increases in the cytosol.
D. A single twitch in skeletal muscle lasts the same length of time as the action potential that causes it.
E. The powerstroke of the cross-bridge cycle occurs simultaneously with ATP being hydrolyzed into ADP and Pi.
C
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a. bone is one example. b. blood is one example. c. hemoglobin can be found in the extracellular material. d. there are 3 different types of muscle e. it is not a primary tissue type.
An action potential is ________
A) a repolarization of the cell membrane B) a rapid depolarization and repolarization of the cell membrane that is propagated C) a refractory period of the cell membrane D) a depolarization of the cell membrane
The lack of adequate surfactant can result in ________
A) adenocarcinoma B) chronic obstructive pulmonary disease (COPD) C) tuberculosis D) asthma E) infant respiratory distress syndrome (IRDS)
What is the first structure of a reflex arc?
A. Motor neuron B. Receptor C. Effector (muscles or glands) D. Sensory neuron