Uterine muscle responsiveness to oxytocin
a. is enhanced by an increased in estrogen/progesterone ratio
b. is prevented by high prostaglandin levels during pregnancy
c. is decreased by down-regulation of oxytocin receptors during the third trimester
d. is enhanced by decreased estrogen/progesterone ratio
e. is independent of estrogen/progesterone ratio

a. is enhanced by an increased in estrogen/progesterone ratio

Explanation:

The average duration of human pregnancy is about 9 months or we can say 38 weeks/266 days. This period is called as the gestation period. At the end of pregnancy vigorous contraction of the uterus result in expulsion or delivery of the baby. It is called parturition. Parturition is a neuroendocrine mechanism.

During pregnancy uterine contractions are inhibited due to the high progesterone levels. Progesterone maintains the endometrium and prevents contraction of myometrium. At the end of last trimester, the progesterone levels plateau and then drops whereas estrogen levels continue to rise.

As a result the E/P ratio increases which makes the myometrium more sensitive to contraction stimuli.

The decreases levels of progesterone may lead to Braxton Hicks contraction which is nothing but false labor. Meanwhile, oxytocin hormone is secreted by the posterior pituitary gland which induces the contraction of myometrium.

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interphase   is the cell cycle stage in which the cell acquires nutrients, creates and uses proteins and other molecules and starts the process of cell division by replicating the dna. it is the longest stage in the eukaryote cell cycle.

the following   can go wrong during interphase:   a base pair could be mismatched during the duplication process causing a mutation.   correct answer: c

explanation: