Sensory capacities, motor responses, respiratory, circulatory, and endocrine systems are considered elements of which of the following systems?

How many stages of sleep are there (including REM sleep)?

a. 4 b. 5 c. 6 d. 7 e. 8

____________ works in tandem with estrogen to regulate a woman's menstrual cycle and sexual response

a. Progesterone b. Estradiol c. Testosterone d. Androgens