Norepinephrine is considered a positive chronotropic agent because it causes
A. less calcium to enter heart cells, which leads to lower risk of heart attack.
B. more forceful contractions during each heart rate.
C. an increase in the firing rate of SA node cells.
D. thyroid hormone to have a steadying effect on heart activity.
E. heart cell membrane potentials to become more positive during action potentials.
C
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An all-or-none response to a threshold stimulus is characteristic of ________.
A. individual muscle fibers B. large muscles C. small muscles D. None of the choices are correct.
Blood within the pulmonary veins returns to the ________.
Fill in the blank(s) with the appropriate word(s).
Overseeing the postural muscles of the body and making rapid adjustments to maintain balance and equilibrium are functions of the
A) cerebrum. B) midbrain. C) cerebellum. D) pons. E) medulla oblongata.
Stimulation of the reticular formation results in
A) increased consciousness. B) sleep. C) coma. D) decreased cerebral function. E) All of the above.