With regard to the action of hormones and neurotransmitters on cellular receptors, which of these describes "amplification"?
A. When the extracellular concentration of a chemical messenger reaches a very high level, it overwhelms transporter molecules and the chemical floods into the cell.
B. Only hydrophilic first-messenger molecules can activate second-messenger molecules within the cell cytosol.
C. A single first-messenger molecule activates multiple second-messenger molecules, each of which activate thousands of enzymes.
D. Some cellular receptors have such low affinity for chemical ligands that it can require a million or more molecules to activate them.
C
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The arachnoid villi are found in the superior sagittal dural sinuses.
Answer the following statement true (T) or false (F)
When the palatine processes of the maxillary bones do not fuse properly, resulting in an opening between the oral and nasal cavities, the condition is known as
A. cleft chin. B. deviated septum. C. cleft lip. D. cleft palate. E. clogged sinus.
Which of the listed events occurs last?
A. Ovulation occurs. B. Estrogen produced by theca interna cells increases. C. FSH/LH positive-feedback loops produce a series of FSH/LH surges. D. FSH and LH levels increase. E. GnRH secretion is stimulated.
What is inflammation?
A. Physical suffering or distress due to injury or illness B. A defense mechanism to warn the person that there is a problem C. The decrease of blood flow to an injured area D. The body's normal immune response to injury and disease