Which of the following statements regarding contraction of a skeletal muscle fiber is TRUE?
A. Some contractions occur without cross-bridge activation.
B. Contracting muscle fibers do not always shorten.
C. Contraction only occurs following summation of action potentials from many motor neurons.
D. Contraction does not always require the occurrence of an action potential.
E. Thick filaments shorten when muscle cells contract.
Answer: B
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Situs inversus is a condition in which __________.
A. an individual has no lenses in the eye. B. the kidney is flipped anterior to posterior. C. the organs of the thoracic and abdominal cavities are reversed between right and left. D. the appendix is affixed to the small intestine instead of the large intestine. E. an individual has incessant and painful heartburn.
The ________ principle states that the properties of the action potential are independent of the relative strength of the depolarizing stimulus.
Fill in the blank(s) with the appropriate word(s).
During passive expiration
a. diaphragm relaxes. b. external intercostal muscles relax. c. internal intercostals muscles relax. d. two of these. e. all of these.
Which of the following types of membranes found in the human body does NOT contain epithelial tissue?
a) Mucous membrane b) Serous membrane c) Cutaneous membrane d) Synovial membrane