Urinary and digestive systems - Essay Example

Mechanism of secretion of hydrogen ions in the renal system Hydrogen ions in the body are produced by the normal metabolic processes. The renal system is responsible for regulating the concentration of hydrogen ions in the body to prevent acidosis. The concentration of hydrogen ions is regulated in the proximal tubule and in the distal tubule. Bicarbonate from the body is filtered in the kidneys. However, it is not excreted and most of it is reabsorbed in the proximal tubules. A small percentage of the bicarbonate is reabsorbed in the collecting ducts and in the intercalated cells of the distal tubule. The bicarbonate is a product of dissociation of carbonic acid which is formed by the action of carbonic anhydrase on water and carbon dioxide. In the tubular lumen, hydrogen ions combine with bicarbonate to form weak carbonic acid. The acid then dissociates into water and carbon dioxide and the gas diffuses through the membranes. Endocrine gland connections to the renal system The renal system is connected to the endocrine system through the pituitary and the adrenal glands. The adrenal cortex secretes aldosterone which is important in water balance. The pituitary gland secretes anti-diuretic hormone (ADH). The two hormones act by regulating the volume of water that is either reabsorbed or excreted in the kidneys. Decreased water intake or increased re-absorption of sodium causes a decrease in blood volume and an increased osmolality. In turn, chemo-receptors in the hypothalamus are stimulated and they synthesize ADH which is stored and released by the pituitary glands. Increased secretion of aldosterone results in increased re-absorption of sodium ions in the kidneys which increases the osmolality. This causes the release of ADH if the osmolality rises beyond normal levels which lead to decreased resorption of sodium and increased absorption of water (Class notes 367). Why we do not pass urine as much in hot weather as in cold weather In hot weather, our bodies lose a lot of water through sweating in an attempt to cool of the body. This results in a state of general dehydration in the body. The amount of urine produced per day is proportional to the amount of water that we take. The decreased amount of water correlates to the decreased volumes and frequency of urination as less amounts of water are excreted through the kidneys (Class notes 357). During cold seasons, the body is trying to reduce heat loss. A lot of energy in form of heat is lost during sweating. Water that is lost in the cooling process is conserved in the body and in an attempt to regulate water volumes in the body it is lost through renal secretion hence increased urine volumes and increased urinating frequency. Micturition and defecation reflexes The micturition reflex basically involves a pathway of impulses from a stretched bladder to the sacral region of spinal cord and then back to the bladder. The first reflex is stretch reflex where the walls of the bladder stretch due to increasing volume sending an impulse to the sacral region of the spinal cord. This activates parasympathetic neurons from the spinal cord to the bladder causing contraction of the smooth muscle on bladder wall to contract. Sensory signals from spinal cord stimulate ascending pathways to cerebellum and pons which results in a conscious desire to urinate. The external urinary sphincter relaxes releasing urine into the urethra. Defecation reflex Mass movement of food in the colon stimulates the defecation reflex. Presence of feces in the rectum causes stretch which stimulates both parasympathetic and local reflexes. There is a resulting contraction of rectum and the internal anal sphincter relaxes forcing the feces out (Class notes 336). The external sphincter also relaxes and defecation is achieved through peristalsis in rectum and increased abdominal pressure. Effect of alcohol consumption on urine production Alcohol increases urine production as it inhibits production of antidiuretic hormone in the pituitary gland. Antidiuretic hormone causes decreased reabsorption of sodium ions in the renal tubules. As a result of decreased sodium ion reabsoption, there is decreased reabsoption of water. Most of the water that is reabsorbed in the kidneys is through osmosis. Thus, decreased sodium ions in the tubules lead to decreased osmolality and thus, less attraction of water ions. Alcohol inhibits release of antidiuretic hormone and this relates to the increased urine production due to increased water retention in the kidneys. It is, therefore, advisable for people to take enough water while taking alcohol to avoid dehydration. Effect of caffeine on urine production Caffeine is a common ingredient in beverages that we take including coffee and some soft drinks. Caffeine like alcohol is also a diuretic. That is, it causes increased urine production and thus, increased frequency in urination. Caffeine causes increased glomerular blood pressure and also an increase in blood pressure in the kidneys. As a result, there is increased blood filtration. In an attempt to regulate the increased blood pressure, the kidney secretes a lot of water which leads to increased urine production. Processes involved in urine production There are three main processes which include glomerular filtration, tubular reabsorption, and secretion and they take place in the renal tubules (Class notes 359). Blood to the glomerular vessels take with them body wastes which are filtered. Most of the water is reabsorbed back into the blood system in the descending tubules. The renal process also secretes body ions and urea which are secreted with the water in form of urine. In the ascending tubules, reabsorption of water and sodium ions takes place. Other waste products that have not been reabsorbed pass through the conducting duct to the bladder where they form urine. Depending on the amount of water that has been reabsorbed, the urine can be either dilute or concentrated. Hydrogen ions are also secreted in urine in form of ammonium. Reason as to why people with high blood pressure should avoid taking licorice Licorice leads to the formation of a compound that has the same effect as aldosterne. Aldosterone in the body causes retention of sodium ions in the body. In the same way, licorice will cause sodium retention in the body and water retention through osmosis. This will lead to increased blood volume and thus increased blood pressure. Importance of Sodium balance Sodium balance is important as it determines the amount of water that is secreted and reabsorbed. Increased retention of water can lead to water toxicity and cell death due to hypotonic environment (Class notes 364). Decreased water retention on the other hand, causes increased plasma osmolality and this could lead to cell death as well. Works Cited Class text book Read More