Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber? 1. Tropomyosin shifts and unblocks the cross-bridge binding sites. 2. Calcium is released and binds to the troponin complex
3. Transverse tubules depolarize the sarcoplasmic reticulum. 4. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP. 5. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane. A) 1 ? 2 ? 3 ? 4 ? 5
B) 2 ? 1 ? 3 ? 5 ? 4
C) 2 ? 3 ? 4 ? 1 ? 5
D) 5 ? 3 ? 2 ? 1 ? 4
D
You might also like to view...
Fuels such as gasoline are nonpolar and high in energy because they are largely composed of
A. sulfates. B. hydrocarbons. C. carboxylic acids. D. amines. E. carbonyls.
Why do most plants produce large numbers of seeds?
a. Most seeds are not viable. b. Most of a plants seeds are produced as food for animals that disperse the seed. c. Most plants have many flowers. d. Most plants only flower once e. Few seeds survive, germinate and grow into mature individuals.
Antidiuretic hormone:
a. promotes processes that lead to an increase in the volume of urine b. makes the distal tubule and collecting ducts more permeable to water c. acts on the proximal tubules of nephrons in the kidney d. is produced by the adrenal cortex e. changes the water permeability of the ascending limb of the loop of Henle
Exhalation _____
a. is always active b. is always passive c. may be both active and passive d. compresses alveoli e. may be both active and passive, and compresses alveoli