Tag: control and coordination in living organisms

Undersecretion of insulin causes diabetes mellitus type I while myxedema is caused by thyroxine deficiency in adults. Hyposecretion of parathyroid hormone causes increased excitability of muscles and their sustained contraction referred to as parathyroid tetany. Luteinizing hormone deficiency causes failure of ovulation as LH surge during midcycle stimulates rupture of Graffian follicle. 

Puberty begins with a surge in hormone production, which in turn causes a number of physical changes. It is the stage in life in which a child develops secondary sex characteristics as his or her hormonal balance shifts strongly towards an adult state. This is triggered by the pituitary gland which secretes a surge of hormonal agents into the blood stream, initiating a chain reaction. The male and female gonads are subsequently activated, which puts them into a state of rapid growth and development. The testes release testosterone and the ovaries release estrogen. The production of these hormones increases gradually until sexual maturation is met.

The hypothalamus is the control centre for many autonomic functions of the peripheral nervous system. Connections with structures of the endocrine and nervous systems enable the hypothalamus to play a vital role in maintaining homeostasis. The hormones produced by this area of the brain govern body temperature, thirst, hunger, sleep, circadian rhythm, moods, sex drive, and the release of other hormones in the body. Hence, if hypothalamus is damaged in an accident, control of water balance, hunger and body temperature will be lost. 

The synthesis and secretion of estrogen is stimulated by follicle-stimulating hormone (FSH), which is, in turn, controlled by the hypothalamic gonadotropin releasing hormone (GnRH).

Trophoblast refers to outer cells of a blastocyst that serve in placenta formation in the beginning of the second trimester. It secretes human chorionic gonadotropin that ensures persistence of the corpus luteum. The later serves to secrete ovarian hormone estrogen, progesterone, and relaxin that are required to maintain pregnancy. Hence, removal of ovaries after 4th month would not affect the pregnancy. The correct answer is C.

FSH is primarily involved in stimulating the growth of ovarian follicles, while LH induces ovulation. At ovulation, the ovum or egg is released and the ruptured follicle is transformed into a corpus luteum, which secretes progesterone as its main product. 

Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone (LH). 

Gonadotropin-releasing hormone (GnRH) is secreted by the hypothalamus and stimulates the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary gland. 

The corpus luteum in the ovaries is the major site of progesterone production in humans, progesterone is also produced in smaller quantities by the ovaries themselves, the adrenal glands and, during pregnancy, the placenta.

Progesterone belongs to a group of steroid hormones called as progestogens. It is mainly secreted by the corpus luteum in the ovary during the second half of the menstrual cycle. It plays important roles in the menstrual cycle and in maintaining the early stages of pregnancy. The progesterone prepares the body for pregnancy in the event, that the released egg is fertilised. If the egg is not fertilised, the corpus luteum breaks down, the production of progesterone falls and a new menstrual cycle begins. Hence, progesterone is called as the 'anti abortion' hormone.