Question

For each of the following hormones identify what gland it is released from, the signal that stimulates release, the target cell/tissue that it acts on, and what result it produces:

Oxytocin

Calcitonin

Gonadotropin releasing hormone

Glucagon

Answer 1

OXYTOCIN:

The oxytocin is synthesized from hypothalamus and released from the posterior pituitary gland. It stimulates uterine smooth muscle and the muscle cells of lactating breast during and after parturition. During parturition, in response to the increasing distension of sensory stretch receptors in uterine cervix by baby's head, the oxytocin is released. This stimulates more forceful uterine contractions and greater stretching of uterine cervix.

                                    The suckling generates the sensory impulses that are transmitted from breast to hypothalamus. The impulses trigger the release of oxytocin from posterior pituitary. The oxytocin stimulates the contraction of myoepithelial cells around the glandular cells and ducts to contract, ejecting milk.

CALCITONIN:

                       The calcitonin is secreted by the parafollicular cells in the thyroid gland. It acts on the bones and kidneys to reduce the blood calcium level, when it is raised. It reduces the reabsorption of calcium from bones and inhibits reabsorption of calcium by renal tubules. Release of calcitonin is stimulated by increase in blood calcium level.

GLUCAGON:  

                     The glucagon is released by the alpha cells of pancreatic islets, when there is a low blood glucose level. It increases the blood glucose level by conversion of glycogen to glucose in liver and skeletal muscles and by gluconeogenesis.