Which of the following situations represents negative feedback?
a. Hormone A stimulates hormone B; hormone B inhibits hormone C.
b. Hormone A inhibits hormone B; hormone B inhibits hormone A.
c. Hormone A stimulates hormone B; hormone B inhibits hormone A.
d. Hormone A inhibits hormone B; hormone B inhibits hormone C.
e. Hormone A stimulates hormone B; hormone B stimulates hormone A.
C
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What is the purpose of motor nerve varicosities as they relate to smooth muscle?
A. They link the thin filaments to the inside of the sarcolemma in smooth muscle. B. They reabsorb the decomposition products of acetylcholine after acetylcholinesterase breaks it down. C. They enable each cardiac myocyte to directly stimulate its neighbors. D. They release neurotransmitter onto smooth muscle cells. E. They prevent single-unit smooth muscle cells from pulling apart.
Which mature cell has no nucleus, no mitochondria and no ribosomes?
A) erythrocyte B) leukocyte C) platelet D) thrombocyte E) neutrophil
What is the function of overlapping endothelial cells in lymphatic capillaries?
A) Overlapping endothelial cells strengthen the walls of the lymphatic capillaries so they are not distorted in tissues. B) Overlapping endothelial cells act as one-way valves that permit the entry of fluids and solutes but prevent their return to the intercellular spaces. C) Overlapping endothelial cells act as one-way valves that permit the exit of fluids and solutes but prevent their entry into the capillary. D) Overlapping endothelial cells allow large proteins to enter the lymphatic capillaries to be transported to the venous system. E) Overlapping endothelial cells produce tight junctions that prevent the movement of lymph into or out of the capillary.
Renewal or modification of the cell membrane is a function of the
A) microtubules. B) mitochondria. C) rough endoplasmic reticulum. D) ribosomes. E) Golgi apparatus.