21.Mineralocorticoids are a class of steroid hormones characterised by their similarity to aldosterone and their influence on salt and water balancesThe name mineralocorticoid derives from early observations that these hormones were involved in the retention of sodium, a mineral. The primary endogenous mineralocorticoid is aldosterone, although a number of other endogenous hormones (including progesterone and deoxycorticosterone) have mineralocorticoid function.Aldosterone acts on the kidneys to provide active reabsorption of sodium and an associated passive reabsorption of water, as well as the active secretion of potassium in the principal cells of the cortical collecting tubule and active secretion of protons via proton ATPases in the lumenal membrane of the intercalated cells of the collecting tubule. This in turn results in an increase of blood pressure and blood volume.Aldosterone is produced in the cortex of the adrenal gland and its secretion is mediated principally by angiotensin but also by adrenocorticotrophic hormone (ACTH) and local potassium levelsAddison’s diseaseis a rare, chronic endocrine disorder wherein the adrenal glands produce insufficient steroid hormones Lifelong, continuous treatment with steroid replacement therapy is required, with regular follow-up treatment and monitoring for other health problemsAldosteronism is a syndrome of high blood pressure and low blood potassium levels caused by an excess of aldosteron.
22. Estrogens are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidalEstrogens are synthesized in all vertebrates[1] as well as some insectsLike all steroid hormones, estrogens readily diffuse across the cell membrane. Once inside the cell, they bind to and activate estrogen receptors which in turn modulate the expression of many genes. Estrone ( E1) is one of several natural estrogensEstrone is relevant to health and disease states because of its conversion to estrone sulfate, a long-lived derivative. Estrone sulfate acts as a reservoir that can be converted as needed to the more active estradiol. Estrone is the predominant estrogen in postmenopausal women Estradiol (E2) is the 2nd predominant sex hormone present in females when naturally produced, but becomes estrone when taken orallycomprises 80% of the naturally occuring estrogens in premenopausal women Estradiol has not only a critical impact on reproductive and sexual functioning, but also affects other organs, including the bones. Estriol is one of the three main estrogens produced by the human bodys only produced in significant amounts during pregnancy as it is made by the placenta. Levels of estriol in non-pregnant women do not change much after menopause, and levels are not significantly different from levels in men.
23. androgens: are produced in the zona reticularis. The most important androgens include:
Testosterone: a hormone with a wide variety of effects, ranging from enhancing muscle mass and stimulation of cell growth to the development of the secondary sex characteristics. Synthesis: Like other steroid hormones, testosterone is derived from cholesterol (see figure to the right).[64] The first step in the biosynthesis involves the oxidative cleavage of the sidechain of cholesterol by CYP11A, a mitochondrial cytochrome P450 oxidase with the loss of six carbon atoms to give pregnenolone. In the next step, two additional carbon atoms are removed by the CYP17A enzyme in the endoplasmic reticulum to yield a variety of C19 steroids.[65] In addition, the 3-hydroxyl group is oxidized by 3-β-HSD to produce androstenedione. In the final and rate limiting step, the C-17 keto group androstenedione is reduced by17-β hydroxysteroid dehydrogenase to yield testosterone. Regulation: In males, testosterone is primarily synthesized in Leydig cells. The number of Leydig cells in turn is regulated by luteinizing hormone (LH) and follicle stimulating hormone (FSH).
Dihydrotestosterone (DHT): a metabolite of testosterone, and a more potent androgen than testosterone in that it binds more strongly to androgen receptors.
24. Thyroid hormones: thyroxine (T4) and triiodothyronine (T3), are tyrosine-based hormones produced by the thyroid glandprimarily responsible for regulation of metabolism. An important component in the synthesis of thyroid hormones is iodine
Binging in blood: Unlike the water-soluble hormones, the lipophilic steroid and thyroid hormones do not travel dissolved in the aqueous portion of the plasma; rather, they are transported to their target cells attached to
plasma carrier proteins. These hormones must then dissociate from their carrier proteins in the blood in order to pass through the lipid component of the plasma membrane and enter the target cell, within which their receptor proteins are located.
Functions: The thyronines act on nearly every cell in the body. They act to increase the basal metabolic rate, affect protein synthesis, help regulate long bone growth (synergy with growth hormone), neuronal maturation and increase the body's sensitivity to catecholamines (such as adrenaline) by permissiveness. The thyroid hormones are essential to proper development and differentiation of all cells of the human body. These hormones also regulateprotein, fat, and carbohydrate metabolism, affecting how human cells use energetic compounds. They also stimulate vitamin metabolism. Numerous physiological and pathological stimuli influence thyroid hormone synthesis.
Disorders: Both excess and deficiency of thyroxine can cause disorders.
Hyperthyroidism (an example is Graves Disease) is the clinical syndrome caused by an excess of circulating free thyroxine, free triiodothyronine, or both. It is a common disorder that affects approximately 2% of women and 0.2% of men. Thyrotoxicosis is often used interchangeably with hyperthyroidism, but there are subtle differences. Although thyrotoxicosis also refers to an increase in circulating thyroid hormones, it can be caused by the intake of thyroxine tablets or by an over-active thyroid, whereas hyperthyroidism refers solely to an over-active thyroid.
Hypothyroidism (an example is Hashimoto's thyroiditis) is the case where there is a deficiency of thyroxine, triiodiothyronine, or both.
Clinical depression can sometimes be caused by hypothyroidism[3]. Some research[4] has shown that T3 is found in the junctions of synapses, and regulates the amounts and activity of serotonin, norepinephrine, and Gamma-aminobutyric acid (GABA) in the brain.
Preterm births can suffer neurodevelopmental disorders due to lack of maternal thyroid hormones, at a time when their own thyroid is unable to meet their postnatal needs
Thyroid-stimulating hormone (TSH) from the anterior pituitary stimulates the thyroid to secrete thyroxine; however, it also exerts a trophic (growth-stimulating) effect on the thyroid. This trophic effect is evident in people who develop an iodine-deficiency (endemic) goiter, or abnormal growth of the thyroid gland. In the absence of sufficient dietary iodine, the thyroid cannot produce adequate amounts of T4 and T3. The resulting lack of negative feedback inhibition causes abnormally high levels of TSH secretion, which in turn stimulates the abnormal growth of the thyroid.
25. CALCIUM: PTH in bones: It enhances the release of calcium from the large reservoir contained in the bones.[7] Bone resorption is the normal destruction of bone by osteoclasts, which are indirectly stimulated by PTH. Stimulation is indirect since osteoclasts do not have a receptor for PTH; rather, PTH binds to osteoblasts, the cells responsible for creating bone. Binding stimulates osteoblasts to increase their expression of RANKL and inhibits their expression of Osteoprotegerin(OPG). OPG binds to RANKL and blocks it from interacting with RANK, a receptor for RANKL. The binding of RANKL to RANK (facilitated by the decreased amount of OPG) stimulates these osteoclast precursors to fuse, forming new osteoclasts which ultimately enhances bone resorption. CT a) Bone mineral metabolism: - Protect against calcium loss from skeleton during periods of calcium mobilization, such as pregnancy and, especially, lactation b) Serum calcium level regulation - Prevent postprandial hypercalcemia resulting from absorption of Ca2+ from foods during a meal - Vitamin D regulation
26. Rickets is a softening of bones in children due to deficiency or impaired metabolism of vitamin D, phosphorus or calcium, potentially leading to fractures and deformity. Rickets is among the most frequent childhood diseases in many developing countries. The predominant cause is a vitamin D deficiency, but lack of adequate calcium in the diet may also lead to rickets (cases of severe diarrhea and vomiting may be the cause of the deficiency). Although it can occur in adults, the majority of cases occur in children suffering from severe malnutrition, usually resulting from famine or starvation during the early stages of childhood. Osteomalacia is the term used to describe a similar condition occurring in adults, generally due to a deficiency of vitamin D.
Osteoporosis is a disease of bones that leads to an increased risk of fracture.[1] In osteoporosis the bone mineral density (BMD) is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered. The disease may be classified as primary type 1, primary type 2, or secondary.
Hypothyroidism is the underproduction of the thyroid hormones T3 and T4. Hypothyroid disorders may occur as a result of congenital thyroid abnormalities (see congenital hypothyroidism), autoimmune disorders such as Hashimoto's thyroiditis, iodine deficiency (more likely in poorer countries) or the removal of the thyroid following surgery to treat severe hyperthyroidism and/or thyroid cancer. Typical symptoms are abnormal weight gain, tiredness, baldness, cold intolerance, and bradycardia. Hypothyroidism is treated with hormone replacement therapy, such as levothyroxine, which is typically required for the rest of the patient's life. Thyroid hormone treatment is given under the care of a physician and may take a few weeks to become effective.
Hyperthyroidism, or overactive thyroid, is the overproduction of the thyroid hormones T3 and T4, and is most commonly caused by the development of Graves' disease, an autoimmune disease in which antibodies are produced which stimulate the thyroid to secrete excessive quantities of thyroid hormones. The disease can result in the formation of a toxic goiter as a result of thyroid growth in response to a lack of negative feedback mechanisms. It presents with symptoms such as a thyroid goiter, protruding eyes (exopthalmos), palpitations, excess sweating, diarrhea, weight loss,muscle weakness and unusual sensitivity to heat.
27. eicosanoids are signaling molecules made by oxidation of twenty-carbon essential fatty acids, (EFAs). They exert complex control over many bodily systems, mainly in inflammation or immunity, and as messengers in the central nervous system. The networks of controls that depend upon eicosanoids are among the most complex in the human body.
Eicosanoids derive from either omega-3 (ω-3) or omega-6 (ω-6) EFAs. The ω-6 eicosanoids are generally pro-inflammatory; ω-3's are much less so. The amounts and balance of these fats in a person's diet will affect the body's eicosanoid-controlled functions, with effects on cardiovascular disease, triglycerides, blood pressure, and arthritis. Anti-inflammatory drugs such asaspirin and other NSAIDs act by downregulating eicosanoid synthesis.
There are four families of eicosanoids—the prostaglandins (They are mediators and have a variety of strong physiological effects, such as regulating the contraction and relaxation of smooth muscle tissue.[1]Prostaglandins are not hormones, but autocrine or paracrine, which are locally acting messenger molecules. They differ from hormones in that they are not produced at a discrete site but in many places throughout the human body), prostacyclins, the thromboxanes (Thromboxane is a vasoconstrictor and a potent hypertensive agent, and it facilitates platelet aggregation.
It is in homeostatic balance in the circulatory system with prostacyclin, a related compound. The mechanism of secretion of thromboxanes from platelets is still unclear.
Leukotrienes act principally on a subfamily of G protein-coupled receptors. They may also act upon peroxisome proliferator-activated receptors. Leukotrienes are involved in asthmatic and allergic reactions and act to sustain inflammatory reactions.For each, there are two or three separate series, derived either from an ω-3 or ω-6 EFA. These series' different activities largely explain the health effects of ω-3 and ω-6 fats
28. The production of saliva is stimulated both by the sympathetic nervous system and the parasympathetic.The saliva stimulated by sympathetic innervation is thicker, and saliva stimulated parasympathetically is more watery.Sympathetic stimulation of saliva is to facilitate respiration, whereas parasympathetic stimulation is to facilitate digestion.Parasympathetic stimulation leads to acetylcholine (ACh) release onto the salivary acinar cells. ACh binds to muscarinic receptors and causes an increased intracellular calcium ion concentration (through the IP3/DAG second messenger system). Increased calcium causes vesicles within the cells to fuse with the apical cell membrane leading to secretion formation. ACh also causes the salivary gland to release kallikrein, an enzyme that converts kininogen to lysyl-bradykinin. Lysyl-bradykinin acts upons blood vessels and capillaries of the salivary gland to generate vasodilation and increased capillary permeability respectively. The resulting increased blood flow to the acinar allows production of more saliva. Lastly, both parasympathetic and sympathetic nervous stimulation can lead to myoepitheilium contraction which causes the expulsion of secretions from the secretory acinus into the ducts and eventually to the oral cavity.Saliva production may also be pharmacologically stimulated by so called sialagogues. It can also be suppressed by so called antisialagogues
29. The digestive functions of saliva include moistening food and helping to create a food bolus, so it can be swallowed easily. Saliva contains the enzyme amylase (also called ptyalin) that breaks up starch into sugar. Thus, digestion of food begins in the mouth. Salivary glands also secrete salivary lipase (a more potent form of lipase) to start fat digestion. Salivary lipase plays a large role in fat digestion in new-borns as their pancreatic lipase still has some time to develop. It also has a protective function, helping to prevent bacterial build-up on the teeth and washing away adhered food particles A common belief is that saliva contained in the mouth has natural disinfectants, which leads people to believe it is beneficial to "lick their wounds". Researchers at the University of Florida at Gainesville have discovered a protein called nerve growth factor (NGF) in the saliva of mice. Wounds doused with NGF healed twice as fast as untreated and unlicked wounds; therefore, saliva can help to heal wounds in some species. NGF has not been found in human saliva; however, researchers find human saliva contains such antibacterial agents as secretory IgA, lactoferrin, lysozyme and peroxidase. It has not been shown that human licking of wounds disinfects them, but licking is likely to help clean the wound by removing larger contaminants such as dirt and may help to directly remove infective bodies by brushing them away. Therefore, licking would be a way of wiping off pathogens, useful if clean water is not available to the animal or person.The mouth of animals is the habitat of many bacteria, some pathogenic. Some diseases, such as herpes, can be transmitted through the mouth. Animal (including human) bites are routinely treated with systemic antibiotics because of the risk of septicemia.Hormonal function-Saliva secretes Gustin hormone which is thought to play a role in the development of taste buds - Epidermal growth factor or EGF · Various enzymes. There are three major enzymes found in saliva. α-amylase (EC3.2.1.1). Amylase starts the digestion of starch and lipase fat before the food is even swallowed. It has a pH optima of 7.4. lingual lipase. Lingual lipase has a pH optimum ~4.0 so it is not activated until entering the acidic environment of the stomach. Antimicrobial enzymes that kill bacteria. Lysozyme Salivary lactoperoxidase Lactoferrin Immunoglobulin A Proline-rich proteins (function in enamel formation, Ca2+-binding, microbe killing and lubrication) Minor enzymes include salivary acid phosphatases A+B, N-acetylmuramoyl-L-alanine amidase, NAD(P)H dehydrogenase (quinone), superoxide dismutase, glutathione transferase, class 3 aldehyde dehydrogenase, glucose-6-phosphate isomerase, and tissue kallikrein (function unknown). Cells: Possibly as much as 8 million human and 500 million bacterial cells per mL. The presence of bacterial products (small organic acids, amines, and thiols) causes saliva to sometimes exhibit foul odor. Opiorphin, a newly researched pain-killing substance found in human saliva.