Question

question 1
which of the following statements is not true of the pineal gland?
it is located on the dorsal aspect of the diencephalon.
melatonin is stimulated by the presence of sunlight.
it produces melatonin.
all of the above are true of the pineal gland.
question 2
one of the few hormones that functions on a positive - feedback loop is:
adh.
calcitonin.
oxtocin.
insulin.
question 3
which is not true of the hormone somatostatin?
it is produced by the delta cells of the pancreas.
it inhibits the secretion of glucagon.
it stimulates the secretion of insulin.
both b and c are not true of the hormone somatostatin.

Explanation:

Question 1

The pineal gland is located on the dorsal aspect of the diencephalon and produces melatonin. Melatonin production is inhibited by sunlight, not stimulated.

Oxytocin functions on a positive - feedback loop. For example, during childbirth, oxytocin release leads to uterine contractions, and uterine contractions further stimulate oxytocin release. ADH (antidiuretic hormone) works on a negative - feedback loop to regulate water balance. Calcitonin helps in lowering blood calcium levels through a negative - feedback mechanism. Insulin also operates on a negative - feedback loop to regulate blood glucose.

Somatostatin is produced by the delta cells of the pancreas. It inhibits the secretion of both glucagon and insulin (not stimulates insulin secretion).

Answer:

Melatonin is stimulated by the presence of sunlight.

Question 2