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Homeostasis-is the process of organisms maintaining a stable environment while existing in an environment that is constantly fluctuating. Regulation includes. -Temperature is regulated. -Internal environment is regulated for nitrogenous wastes, salt, glucose, gasses like oxygen and carbon dioxide. This is involves with the kidney and liver. Also hormones and the nervous system aid in homeostasis. -Glucose and other nutrients are regulated by the vertebrate liver. Most nutrients (except lipids) are transported from the small intestines to the liver via the hepatic portal vein. The liver has the ability to convert nutrients from one form to another. It distributes the nutrients so that the blood leaving the liver consistently has the same concentration of nutrients. For example the blood leaving the liver usually has glucose concentration of 90 mg/100 mL, regardless of the amount of sugar in the meal. Glucose regulation is under the influence of hormones such as insulin which lowers glucose levels in the blood and glucagon increases glucose level in the blood. If there is too much glucose in the blood from a meal, the liver will convert to glycogen to be stored until needed. Once the glycogen reaches the maximum, then it is converted to lipids which are then stored in adipose tissue. There 24 hrs. of glycogen reserves for the body. -The liver also detoxifies alcohol and other poisons. Fat-soluble poison is made water soluble by the liver. It then travels to the gall bladder. From there it is dumped into the small intestines and then absorbed by fiber, finally it will be excreted. -If there is an excess of amino acids, the liver will deaminate the amine group from the amino acid. This ammonia is converted to urea put into the blood stream and then filtered by the kidneys Functions of the liver in homeostasis 1. Regulates blood levels of glucose (glucose<==>glycogen) 2. Has the ability to make glycogen from excess lactic acid produced in exercising 3. Interconvert incoming organic nutrients 4. Deaminates amino acids to form NH3. May convert NH3->urea or uric acid depending on the organism 5. Ability to detoxify some poisonous chemicals 6. Manufactures plasma proteins like globulin, fibrinogen, prothrombin, albumin 7. Manufactures plasma lipids and cholesterol 8. Stores vitamins & iron 9. Forms RBC in embryos 10. Destroys RBC 11. Excrete bile pigments 12. Synthesizes bile salts *The liver is one organ that has the ability to regenerate itself. Osmoregulation is the uptake and loss of water and solutes. Units milliosmoles per liter (mOsm/L). Osmolarity of human blood is 300 mOsm/L while seawater is 1,000 mOsm/L. TermsHyperosmotic-is when one solution has a greater concentration of solutes than a second solution. Hypoosmotic-when one solution is more dilute than a second solution. Isosmotic- two solutions that have the same concentration of solutes. Osmoconformer is one that cannot regulate its uptake of fluids and therefore is isosmotic with environment. Mostly marine organisms are isosmotic because the marine environment is pretty stable and does not fluctuate. Excretion- process of an organism ridding their bodies of metabolic wastes. This process also helps regulate ions such as sodium chloride. Osmoregulator is one that controls its internal osmolarity independent of the environment. Stenohaline organisms are those that cannot tolerate great changes in the molarity of their surrounding environment. Euryhaline organisms are those than can tolerate change in the molarity of their surrounding environment. (Pacific salmon) Most marine invertebrates are osmoconformers •Most marine vertebrates and some invertebrates are osmoregulators •Marine bony fishes are hypoosmotic to sea water •They lose water by osmosis and gain salt by diffusion and from food. •They balance water loss by drinking seawater and excreting salts Marine fish-did not evolve from marine invertebrates but from fresh water fish, therefore their body fluids are diluted (or hypertonic) in comparison to sea water Freshwater animals •Freshwater animals constantly take in water by osmosis from their hypoosmotic environment •They lose salts by diffusion and maintain water balance by excreting large amounts of dilute urine •Salts lost by diffusion are replaced in foods and by uptake across the gills As marine animals migrated to fresh water, natural selection preferred animals that could tolerate more dilute body fluids. Surely you must realize that the first marine animals in fresh water had a tendency to lose salts and H2O, and compensated by constantly replacing them. •Land animals manage water budgets by drinking and eating moist foods and using metabolic water •Desert animals get major water savings from simple anatomical features and behaviors such as a nocturnal life style Terrestrial animals must fight desiccation. Animals obtain water by 1. Drinking H2O 2. Food with H2O 3. Byproduct of cellular respiration Getting rid of nitrogenous wastes. When the liver processes amino acids, it produces ammonia which is extremely toxic. Fresh water fish just flushes the ammonia out of their bodies. Mammals and amphibians form urea and finally urine. Birds and reptiles form uric acid which is insoluble and less H2O is needed for excretion. Also uric acid will not poison embryos in eggs. The kidneys are responsible for filtering the blood and important in homeostasis. Survey of controlling body fluids Protonephridia-flame cell system -Found in planaria, other invertebrates and lancets. Planaria do not have circulatory system, or coelom. They have a simple tubular excretory system call protonephridia. This network of closed tubules lacks internal openings that branch throughout the body. At the end of the smallest branch are found cellular flame cells. -Interstitial fluid passes through a flame cell that is propelled by a current created by the cilia moving inside the flame cell. -The fluid is filtered and moved into excretory ducts. These ducts empty out the body through numerous nephridiopores. -The epithelium lining reabsorbs any salts before the fluid leaves the body. -The epithelium lining reabsorbs any salts before the fluid leaves the body. -Other parasitic species are isotonic to their surroundings, and this flame cell system is used to excrete nitrogenous wastes. Annelids-(segmented worms with a true coelom) include earthworm. -Each segment contains a pair of metanephridia excretory tubules that have internal openings to collect body fluids. The opening collects the fluid from the segment that is anterior to it. -Coelomic fluid enters the ciliated funnel (nephrostome) -The fluid passes through the metanephridium and empties into a storage bladder that empties to the environment via the nephridiopore -As the fluid passes through the metanephridium, a capillary bed which surrounds it reabsorbs essential salts by pumping out of the collecting tubules. - The fluid excreted is hypotonic and dilute to offset the continual uptake of water via osmosis. Arthropods and malpighian tubules -Arthropods (insects) have an open circulatory system. The excretory organs are out pocketing between the midgut and hindgut. These out pocketings are called malpighian tubules. -The malpighian tubules are bathed in hemolymph. -The transport epithelium lining moves solutes (salts and nitrogenous wastes from hemolymph into the tubule's lumen. -The fluid in tubule then passes through the hindgut to the rectum. -Salts and water are reabsorbed across the epithelium of the rectum and dry nitrogenous waste is excreted with feces. The organ that filters the blood in vertebrates is the kidney. When the blood is filtered, it forms a waste liquid called urine. The kidney functions in excretion and osmoregulation. The kidneys in humans are found on the imbedded on the dorsal side of the abdominal cavity. In humans, there is a pair of kidneys, one on each side. They are about the size of a fist. The renal artery brings blood to the kidney and a renal vein returns the blood to the vena cava. The ureter carries the urine to the urinary bladder to be stored. When the bladder empties, the urine is moved from the bladder to the urethra to the outside of the body. The kidney has three distinct layers. The outer most layer is the cortex of the kidney. Below the cortex is the medulla. In the center is the renal pelvis which collects the urine to be sent to the bladder. The filtering unit of kidney is the nephron. There are over 1,000,000 such filtering units in each kidney. -The blood is delivered via an efferent arteriole to a capillary bed called the glomerulus. -The blood leaves the glomerulus via the afferent arteriole forming a second capillary bed called the peritubular capillaries that surrounds the nephron. --The blood then leaves the nephron via a venule. -1,100-1,200 L of blood flows through the kidneys each day. At the beginning of the nephron is Bowman's capsule. This surrounds the glomerulus. Leading from Bowman's capsule is the proximal convoluted tubule (PCT). -From the PCT is the loop of Henle. The filtrate moves down the descending side and then up the ascending side. -The ascending side leads to the distal convoluted tubule (DCT). At the beginning of the nephron is Bowman's capsule. This surrounds the glomerulus. Leading from Bowman's capsule is the proximal convoluted tubule (PCT). -From the PCT is the loop of Henle. The filtrate moves down the descending side and then up the ascending side. -The ascending side leads to the distal convoluted tubule (DCT). The DCT finally empties its fluids into collecting ducts. -The nephron is oriented so that the loop of Henle is pointed toward the pelvis of the kidney. -Cortical nephrons have reduced loops of Henle and are confined to the renal cortex (80%) -Juxtamedullary nephrons have long loops of Henle that extend down through the renal medulla (20%). -The longer the loop of Henle, the more water that is conserved or retained by the body. Kangaroo rats have very long loops of Henle. -The collecting ducts extend down through the cortex, through the medulla, to the pelvis. -There is a salt gradient that becomes more saline as one goes from the renal cortex to the pelvis. -The nephrons process 180 L of filtrate each day. Mechanism of urine formation by the kidney 3 processes 1. Ultrafiltration-Filtered by the glomerulus 2. Reabsorption-Material moving from nephron back into the capillary bed surrounding the nephron. 3. Tubular excretion-Material is transported into the nephron at the convoluted tubules. 1844 Carl Ludwig-Suggested that the glomerulus act as a mechanical filter. The hydrostatic pressure of the glomerulus would push or filter molecules small enough to pass through the pores into Bowman's capsule. If that is correct, then the filtrate should have the same composition of plasma (minus plasma proteins). A.N. Richards was able to insert a microscopic pipette into the capsule to verify this and prove that the filtrate had the concentration of ions and other solutes as in the plasma. Problem-urine the final produce does not have the same concentration of solutes as the filtrate, and also it was determined that 180 liters of filtrate was produced but yet only produced 1-2 liters of urine was excreted a day. Therefore, conclude that H2O, glucose, amino acids were reabsorbed. Water, NaCl, K+ and nutrients were reabsorbed in the PCT. NaCl was reabsorbed in the ascending loop of Henle, and the collecting duct. Some urea is actually reabsorbed by the collecting duct with water. Some solutes are transported into the nephron like NH3, K+, and H+. This is called tubular excretion. It was found that the concentration of Na+ was just slightly lower in the DCT than the PCT. Yet it was found that Na+ was actively pumped out of the ascending loop of Henle. Therefore it was concluded that the salt diffused back around to the descending loop and passively flowed into descending loop because the concentration of Na+ was higher in the surrounding tissue than the loop. Water is permeable in the descending loop of Henle. As the water moves through the descending loop, the surrounding tissue becomes more saline. More water is lost via osmosis and the filtrate becomes very concentrated (from 300 mosmoles/L to 1200 mosmoles/L). In the ascending loop, the loop is impermeable to water BUT the loop actively transports salt out of the filtrate. Because of the removal of salt, the filtrate in the ascending loop has become much more dilute (from 1200 to 100 mosmoles/L). The filtrate is going to go through the salt gradient one more time. but can be reabsorbed in the collecting tubule to concentrate the urine even more. in the collecting tubule to concentrate the urine even more. The permeability of the collection tubule varies and is under the control of hormones. The net effect of this system is to reabsorb water. Over 1,200 L of material (mostly water) is filtered every day but yet on 1-2 L of urine is excreted.Control of Excretion There are three different hormonal systems that help regulate excretion, the ADH, RAAS, and ANP. ADH- This system involves antidiuretic hormone (ADH) produced by the hypothalamus and stored in the pituitary gland. Let’s suppose that your blood becomes more concentrated due to eating some salty food or not drinking fluids. The hypothalamus (found in the brain) releases ADH. This is secreted into the blood stream and makes its way to the kidneys. At the kidneys, ADH will attach to receptor sites on the cells of the collecting tubules. This will cause a reaction involving aquaporins, which will become part of the plasma membrane allowing water to be reabsorbed by the kidneys. This causes urine to become or concentrated. It also causes the sensation of thirst. Drinking will cause the blood to become more dilute. RAAS-Rennin, angiotensin, aldosterone, Another way to regulate electrolytes also involve regulating the blood pressure. There is some sensitive tissue on the artery delivering blood to the glomerulus. This is called the juxtaglomerular apparatus (JGA). When blood pressure drops, the JGA secretes an enzyme, rennin into the blood stream. Rennin causes a plasma protein called angiotensin I to be converted into angiotensin II. Angiotensin II will cause arterioles to constrict and all cause the adrenal gland to release a hormone called aldosterone. Aldosterone causes more Na+ to be reabsorbed which causes water to be reabsorbed by the tissue surrounding from the nephron. This also increases blood volume and ultimately blood pressure. Another hormone, atrial natriuretic peptide (ANP), opposes the RAAS. ANP is released in response to an increase in blood volume and pressure and inhibits the release of renin. This decreases blood pressure.