Answer of Question of the Endocrine System & Chemical Messengers
Q.36. Describe the hormones secreted from the gonads in mammals.
The gonads (ovaries and testes) secrete hormones that help regulate reproductive functions.
In males, the testes secrete testosterone, which acts with luteinizing and follicle — stimulating hormones (LH & FSH) that the adenohypophysis produces to stimulate spermatogenesis. Testosterone is also necessary for the growth and maintenance of the male sex organs; promotes the development and maintenance of sexual behavior, and in humans, stimulates the growth of facial and pubic hair, as well as enlargement of the larynx, which deepens the voice. The testes also produce inhibin, which inhibits the secretion of FSH.
In female, four major classes of ovarian hormones help to regulate reproductive functions.
- Estrogen (estrin, estrone, and estradiol) help regulate the menstrual and estrus cycles and the development of the mammary ‘glands and other female secondary sexual characteristics.
- The progestins (primarily progesterone) also regulate the menstrual and estrus cycles, and the development of the mammary glands, and aid in placenta formation during pregnancy.
3. Relaxin, which is produced in small quantities, softens the opening of the uterus (cervix) at the time of delivery.
iv. The ovaries also produce inhibin, which inhibits the secretion of FSH.
Q.37. Give a brief account of thymus gland.
Ans. The thymus gland, lies under tire breastbone near the heart in humans, is quite
large and conspicuous during childhood. At puberty, when the immune system is well established, the thymus begins to decline, and by adulthood it is largely replaced by adipose and fibrous tissue. Though much reduced in size, the thymus continues to function throughout life.
The major hormonai product of the thymus is a family of peptide hormones, including thymopoietin (TI’) and alphai and beta4 thymosin that appear to be essential for the normal development of the immune system.
Q.38. How the endocrine system and nervous system are related?
Ans. There have been many examples of interactions between the endocrine system and the nervous system. Indeed, the two systems are often inseparable and may function as a single unit. We can synthesize much of our understanding of the chemical communication and coordination in animal bodies by examining three types of relationships between the endocrine system and the nervous system.
- Structural Relationship
Many endocrine glands are made of nervous tissue. The vertebrate hypothalamus and posterior pituitary, and parts of the insect brain, are examples of nerve tissues that secrete hormones into the blood. Other endocrine glands that are not nervous tissue in their present form have evolved from the nervous system. The adrenal medulla is derived from the same cells that produce certain ganglia (clusters of nerve cell bodies outside (he central nervous system).
- Chemical Relationship
Several vertebrate hormones are used as signals by the nervous system as well as by the endocrine system. Norepinephrine, for example, functions in the body both as an adrenal hormone and as a neurotransmitter in the nervous system.
- Functional Relationship
First, the coordinating system controlling some physiological processes involves both nervous and hormonal components arranged in series. For example, milk letdown, the release of milk by a mother during nursing, is controlled by a neuroendocrine reflex: • suckling stimulates sensory cells in the nipples, and nervous signals to the hypothalamus trigger the release of oxytocin from the posterior pituitary.
Second, each system affects the output of the other. We have seen several examples of how the nervous system controls the endocrine glands, including the stimulation of the adrenal medulla. But the endocrine system also affects both the development of the nervous system and its output behaviour.
Q.39. What is diabetes? Describe the forms of diabetes.
Ans. Diabetes Mellitus
Diabetes mellitus, the endocrine disorder, is caused by a deficiency of insulin or a loss of response to insulin in target tissues. The result is high blood glucose — so high, in fact, that the diabetic’s kidneys excrete glucose, which explains why the presence of sugar in urine is one test for diabetes. As more glucose concentrates in the urine, more water is excreted with it, resulting in excessive volumes of urine and persistent thirst. (Diabetes, from the Greek, refers to this copious urination, and mellitus for “honey”, referring to the presence of sugar in the urine). Because glucose is unavailable as a major fuel source for diabetics, fat must serve as the main substrate for cellular respiration. In severe cases of diabetes, acidic metabolites formed during fat breakdown accumulate in the blood, threatening life by lowering blood pH.
There are actually two major forms of diabetes with very different causes:
- Type I diabetes mellitus
Type I diabetes mellitus (insulin dependent diabetes) is an autoimmune disorder, in which the immune system mounts an attack on the cells of the pancreas. This usually occurs rather suddenly during childhood, destroying the person’s ability to produce insulin. Treatment consists of insulin injections, which are usually taken several times daily. Until recently, insulin for injections was extracted from animal pancreases, but genetic engineering has provided a relatively inexpensive source of human insulin by inserting the genes for the hormone into bacteria.
- Type II diabetes mellitus
Type II diabetes mellitus (non — insulin — dependent diabetes) is characterized either by a deficiency of insulin or, more commonly, by reduced responsiveness in target cells due to some change in insulin receptors. Type II diabetes usually occurs after about age 40 becoming more likely with increasing age. More than 90% of diabetics are type II, and many can manage their blood glucose solely by exercise and dietary control. Heredity is a major factor in type II diabetes.