Depolarization of a cardiac muscle cell occurs as the result of
A. a decrease in the permeability of the cell membrane to sodium.
B. the opening of voltage-gated sodium channels and voltage-gated calcium channels.
C. the closure of voltage-gated calcium channels.
D. the opening of voltage-gated potassium channels.
E. the closure of the voltage-gated sodium channels.
B
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A) production of enzymes, clotting factors, and antibodies B) production of energy C) formation of functional molecules like hemoglobin and cytochromes D) production of some hormones
Cancers of epithelial tissues are called
A. sarcomas. B. leukemias. C. lymphomas. D. carcinomas.
The plateau phase seen during the action potential of a cardiac muscle cell is due to the
A. sodium-potassium pump. B. continuing to have open Ca2+ channels. C. opening of Na+ channels. D. closure of Cl? channels. E. closing of Ca2+ channels.
What type of gland excretes products by secretion into the blood?
A. apocrine B. holocrine C. merocrine D. endocrine E. exocrine