Tag: control and coordination in living organisms

The pineal gland or epiphysis synthesizes and secretes melatonin hormone, that communicates information about environmental lighting to various parts of the body. It is attached to the roof of third ventricle in the rear part of brain. It functions as a biological clock and a neurosensory transducer, converting the neural information.  

Hypoparathyroidism is decreased function of the parathyroid glands with underproduction of parathyroid hormone. This can lead to low levels of calcium in the blood, often causing cramping and twitching of muscles or tetany (involuntary muscle contraction).

Tetany is an abnormal condition characterized by periodic painful muscular spasms and tremors, caused by faulty calcium metabolism and associated with diminished function of the parathyroid glands.

Vitamin D increases blood concentrations of calcium. It is generated through the activity of parathyroid hormone within the kidney. The most important effect of vitamin D is to facilitate absorption of calcium from the small intestine. Along with thyroid hormone, vitamin D also enhances fluxes of calcium out of bone.

Parathyroid hormone (PTH), parathormone or parathyrin, is secreted by the chief cells of the parathyroid glands. It acts to increase the concentration of calcium ($Ca^{2+}$) in the blood. Parathormone also inhibits the reabsorption of phosphate by the kidney tubules, thereby decreasing serum phosphate concentrations. This potentiates the ability of parathormone to increase serum calcium concentrations because fewer insoluble calcium-phosphate complexes are formed when serum phosphate concentrations are low.

Parathormone of parathyroid gland reduces the blood phosphate level while increases the blood calcium level. Antagonistic functions of insulin and glucagon hormones of pancreas maintain the homeostasis of blood glucose level. Thyroid hormones regulate the metabolic rate of the body. Thymus hormone serves in the differentiation of lymphocytes present inside the lobules. Thus, the correct answer is D.

A low level of parathyroid hormone (hypoparathyroidism) can cause hypocalcemia, which results when too much calcium is lost in urine or when not enough calcium is moved from bones into the blood. 

Parathyroid hormone is secreted by the parathyroid glands and is the most important regulator of calcium levels in the blood and within the bones. Parathyroid hormone is mainly controlled by the negative feedback of calcium levels in the blood to the parathyroid glands. Low calcium levels in the blood stimulate parathyroid hormone secretion, whereas high calcium levels in the blood prevent the release of parathyroid hormone.

Hypoparathyroidism is the state of decreased secretion or activity of parathyroid hormone (PTH). This leads to decreased blood levels of calcium (hypocalcemia) and increased levels of blood phosphorus (hyperphosphatemia).

Parathyroid hormone (PTH) or parathormone is secreted by the chief cells of the parathyroid glands as a polypeptide containing 84 amino acids. It acts to increase the concentration of calcium in the blood.