Question

provide the Stimulus (how homeostasis is disturbed), 2. Signaling cell, 3. Target cell, 4. Result (how homeostasis is restored) for:

1. ADH
2. Calcitonin
3. T3 & T4
4. Parathyroid Hormone
5. E & NE
6. Insulin
7. Glucagon

Answer 1

Homeostasis is the state of equilibrium which is maintained by the body inorder to carry out all the cellular functions efficiently. The various sensors in the body detect changes in various parameters, report to the central nervous system and the action is taken to bring back the values of parameters to normal. Hormones play an essential role in maintaining homeostasis as they are the chemical messengers to report and also to work in bringing the normal state.

ADH is the anti-diuretic hormone secreted by posterior pituitary gland which regulates the water retention in the body. ADH binds to the receptors of cells in the collecting ducts of the kidneys and it promotes reabsorption of water back into normal circulation.

Calcitonin is secreted by parafollicular cells of thyroid gland which regulates blood calcium levels. The hormone calcitonin binds to the receptors on the osteoclasts cells to inhibit calcium absorption from bones. Thus, calcitonin decreases blood calcium levels by inihibiting the activity of osteoclasts.

The hypothalamus secretes thyrotropin releasing hormone (TRH) which stimulates the anterior pituitary gland to release thyroid stimulating hormone (TSH). The thyroid gland produces thyroxine or (T4) and T3 upon stimulation by TSH. The T3 and T4 hormones regulate metabolism.

Parathyroid Hormone (PTH) produced by parathyroid gland stimulates osteoclasts to increase calcium levels in the blood. PTH is released in response to low blood calcium levels.

Insulin is secreted by beta cells of islets of Langerhans of pancreas which regulates blood glucose levels. It is released in response to high glucose levels in the blood and the binding of insulin to insulin receptors allows glucose inside the cells. Thus, it decreases blood glucose levels.

Glucagon is secreted by alpha cells of islets of Langerhans of pancreas which regulates blood glucose levels. It is released in response to low glucose levels in the blood. Glucagon stimulates glycogen breakdown in order to increase the blood glucose levels.