Which of the following is an example of positive feedback?
A) After eating a meal containing high glucose levels, the pancreas secretes more insulin, a hormone that lowers blood glucose levels.
B) After cutting your finger, the injured tissue releases chemicals that activate platelets in the blood. These activated platelets release chemicals to activate more platelets, leading to the formation of a blood clot.
C) An elevation in blood pressure causes heart rate to decrease, thereby causing blood pressure to decrease.
D) The secretion of the hormone TSH stimulates the thyroid gland to secrete thyroxine. Thyroxine, in turn, inhibits the secretion of TSH.
Answer: B
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The STD characterized by three distinctly different symptomatic stages is the result of infection with
A) Chlamydia trachomatis. B) Leptospira interrogans. C) Treponema carateum. D) Treponema pallidum pallidum. E) Treponema pallidum pertenue.
The average number of sperm that enter the vagina
during an ejaculation is between a. 150,000 and 350,000. b. 1.5 and 3.5 million. c. 15 and 35 million. d. 150 and 350 million. e. 1.5 and 3.5 billion.
Which one of the following types of sequence can be found in a genome?
A. regulatory elements of protein-coding genes B. noncoding introns C. protein-coding exons D. coding sequence for RNAs E. All of the answer options are correct.
2D chromatography is called that because
a. there are two steps: labeling with a radioactive marker and separation via chromatography. b. the molecules are separated into a linear arrangement, meaning two dimensions. c. the process separates the molecules in two directions, first along the x axis and then along the y axis. d. two different solutions are used in the paper chromatography process. e. two different types of radioactive markers must be used.