Homeostasis PDF

HOMEOSTASIS The term homeostasis was introduced by Walter B. Cannon {1871—1945). He described it as a self-regulating process by which biological systems maintain stability while adjusting to the changing conditions. Homeostasis is essential for the continuity of life as it is responsible for...

HOMEOSTASIS The term homeostasis was introduced by Walter B. Cannon {1871—1945). He described it as a self-regulating process by which biological systems maintain stability while adjusting to the changing conditions. Homeostasis is essential for the continuity of life as it is responsible for the stability of body functions according to the environment. Organisms live in terrestrial and aquatic environments. These environments have variable conditions, i.e., moderate to extreme conditions which influence upon the organisms and they tend to develop physical and physiological changes in their body accordingly. In view of the environmental changes, organisms need to maintain their internal body environment up to suitable limits. The body environment comprises of different components including body fluids, tissues, organs, systems etc. These components are physiologically well integrated and efficiently controlled and coordinated by endocrine as well as nervous systems. These systems ensure the proper performance of the homeostatic regulatory functions like osmoregulation, excretion and thermoregulation, in the body and adjust to maintain the balance between the external and internal body environment. 15.JELEMENTS Oé‘HOMEOSTASIS Homeostatic surveillance is based upon necessary physiological check and balance mechanism ofthebody functions that maintain its normal state called feedback system. Feedback mechanism develops through some integrated components i.e., receptors, control center and effectors. Receptors are the sensory organs that are neurologically connected with the nervous system, detect any external or internal environmental changes and send messages to the central nervous system (CNS). CNS act as control center and respond by concerned effector organs to bring back thenormal state of the body. IS. 1.1 Feedback systems Feedback, in biology, a response within a system (molecule, cell, organism, or population) that influences the continued activity or productivity of that system. There are two types of feedback mechanisms that counter act upon each other called positive and negative feedback. The positive feedback isconcerned with the increase or initiate the change ofoutput forany biological process, e.g. if body isinjured and bleeds positive feedback begins by the action of platelets. Platelets reached at the site of injury through circulating blood, recognize the damaged area and begin to stick together to stop the loss of blood and patch up the tear in the wall. Eventually blood clot is formed, the loss of blood iskept to a minimum, and thepositive feedback ends. Positive feedback does not maintain a stable, homeostatic condition rather it intensifies the change that is happening tothe body. Positive feedback cycle is initiated Released chemicals Positive Platelets adhere attract more ,q feedback to site and platelets , loop release chemicals Feedback cycle ends when plug is formed Fig. 15.1 Positive feedback mechanism The Negative feedback suppresses the normal physiological activities to bring body back to normal state e.g. when it is cold out, and body temperature decreases below the set point range. A set point is the physiological value around which the normal range fluctuates. A normal range is the restricted set of values that is optimally healthful and stable. The negative feedback loop will cause the body to shiver producing heat and ultimate body temperature will return within the set point. Effect Sensor 15.2.1 Osmoconfoxmexs and Osmoregulators Oaznoconformers Oaznoregulatora Organisms that have internal Organisms maintain a constant body solute composition equals internal osmotic environment in or isotonic to the external spite of changes in their external environment environment These are marine organisms. They live in marine, fresh water and terrestrial environments. Can survive in wide range of Can survive in a narrow range of salinities salinities £ S. 2. Z. Problems faced by 8smoregulators Fresh water animals have an external hypotonic environment while they retain salts in their body, they have hypertonic internal body environment. In this case water enters the body by endosmosis through their organs like skin and gills and disturbs the internal osmotic balance. This problem isresolved by different adaptations to remove excessive water from the body. Marine animals have hypertonic external environment and they face the problem ofsevere dehydration. Therefore, they need tointake or drink water but in this case another problem develops which is about the retaining salts that enters with water which also imbalance y the osmoregulatory components ofthe body. Terrestrial organisms retain water in their body, while bearing external hot environment they perspire and not only dehydrates but also lose essential salts which disturbs the osmotic balance of the body. lis. 2.3 Methods for osmoregulation in fresh water, mar!lie and terrestrial habitat Osmoregulation in fresh water Habitat Fresh water animals have internal hypertonic and external hypotonic environment. Fresh water fishes face the problem ofosmotic incursion of water from gills and skin and minimize the loss of salt by urine and by diffusion across the gills. The water influx and salt removal are balanced from the kidney by producing dilute urine. The filtration rate in kidney is high and they are specialized to actively  reabsorb salts and send back into the blood. Fresh water organisms also have specialized cells located in their gills and in skin called ionocytes which actively extract Na+, Cl- and Ca' from external medium and excrete (H+) or basic (HCO3-) foracid base balance in the body fluids. Osmoregulation in marine water Habitat Marine animals also need to retain water in their body fortheir metabolic requirements. They have higher concentration of water in their blood than their surrounding environment. They don't gain water like fresh water organisms due to their external hypertonic environment, therefore they intend to drink lotofwater and also digest its salts which are harder than fresh water salts. In marine bony fishes, the gills, kidney and digestive tract are involved in maintenance of body fluid balance, as the main osmoregulatory organs. These fishes are capable of digesting marine salts which are added intheir blood along with water, excessive salts are extracted and remove by specialized rectal glands in intestine and salt glands located in gills. These fishes reabsorb water some salts and excrete very small amount ofurine with excessive salts mainly divalent ions, mainly Mg*+, SO4 , Na*, Cl°, Ca+* from the kidney. I Gain ofwater and Excretion Osmotic water Uptake ofwater and Uptake salt ions from food ofsalt ions loss through gills some ions in food ofsalt ions Osmotic water from gills and other parts gain through gills of body surface and other parts of body surface Gain ofwater arid Excretion of salt ions and Excretion of large salt ions from small amounts ofwater amount ofwater in drinliing seawater in scanty urine from kidneys dilute urine from kidneys itarirte water fJs1zes Fresh water fishes Fig. 15.3 Osmoregulation in marine and freshwater fishes Osmoregulation in terrestrial Habitat Terrestrial animals live in moderate to extreme environmental conditions on land. Some areimmensely exposed toscorching sun and temperature and face the severe problem ofdehydration like in desert while others live in moderate environment but allof them need to conserve water and essential solutes in their body. These organisms can lose water from integument, excretion and exhaling during breathing, therefore they have evolved many adaptations in response to environmental stresses. These adaptations are related with preventing removal of water from skin or body covering, not losing much water by excretion and maintaining osmotic balance ofthe body fluid by metabolic activities within the body. To prevent water loss from the smn they develop water proof external covering as exoskeleton made up ofkeratin, chitin and CaCO3 found invarious arthropods and other organisms. Animals produce excretory waste which require less amount ofwater like uric acid and conserve water through efficient reabsorption in kidney and intestine. Some animals like camel, kangaroo-rat, etc., in the absence of environmental water get ifi through metabolic water by breakdown offats and other compounds during ceflular oxidation reactions as a byproduct. cp Extra Reading Maternal 15.3. 1. EXCRETION Excretion is a process of removal of metaboUc waste produced during biochemical reactions in the body. It is an important homeostatic activity as in broader sense it involves conVofling the osmotic pressure, the balance between inorganic ions and water and maintaining acid base balance ofthe body. Though thewaste includes variety of compounds like CO2, nitrogenous waste including ammonia, urea and uric acid, in a restricted sense, we are going to discuss the removal ofnitrogenous wastes only. 15.3.2. Eacretorjr products in relation to habitat: Animals produce different types of nitrogenous excretory waste. The major fiypes of nitrogenous wastes are ammonia, urea, uric acid, and creatinine. Both wastes and their removal depend upon firsHy, the nature of food like herbivores do not excrete as much wea as carnivores because carnivores eat more protein, and therefor excrete more nitrogen, secondly, availability of water and third the animal's habitat. Nitrogenous waste produced as a byproduct due to the breakdown ofprotein and nucleic acids. Ammonia: Ammonia is an immediate and highly toxic gaseous waste initially produced by the breakdown ofnitrogenous compounds inthe body. Itisexceedingly soluble in fresh water and body fluids and raises the pH therefore should be present in low concentration in the body. Ammonia reduces itstoxicity in water and requires lot of fresh water to dissolved and generate non-toxic ammonium (NH4+) ions, therefore produced in aquatic animals in gaseous form and mostly diffused out from thebody while some amount also excreted through urine as urea. Ammonia isalso produced in terrestrial animals and converted in to another nitrogenous product i.e., urea and excreted through urine from the body. Chemically it is alkaline, corrosive and 100,000 times more toxic than urea. Animals that excrete ammonia are said to be ammonotelic. Urea: Urea CO(NHz)z is the nitrogen containing liquid waste product produced by the breakdown of protein in mammals, amphibians, in some fishes and excreted in urine. It is also called carbamide, neither acidic nor alkaline and highly soluble in water. Liver combines ammonia with CO2 molecule to form some intermediate compounds and then produces urea in the urea cycle or ornithine cycle. Animals produce urea are called ureotelic. Urea isnot only a waste product in the body but also plays important role in the absorption of important ions and water in kidneys. Uric acid: Uric acid is another nitrogenous compound and oxidative metabolic product of purines present in nucleic acids. It is also structurally resembled with purines, weak acidic and less soluble in water than ammonia and urea. It is about 10,000 times less toxic than ammonia. Animals that produce and excrete uric acid are called uricotelic which include reptiles, birds and numerous arthropods like insects etc. Uric acid can be stored in the body tissues without any toxic effect or harm. Excretory wasteo contain uric acid appears thick paste like and needs less amount of water and animals get the advantage to conserve water in their bodies. In humans 75% uric acid is excreted by kidneys and 25% isexcreted by intestine. Protežzzs Nucleic acżzts hEost aquatic žamzaałs, œost Many reptiles aziima1s, including ampbżbšans, sbarba, țincluding birdaJ, most body źžsfzes sozzze body Asžzea insects. land snails ś N H, II C H Ammonia HN II C O Urea O *w'wN H H Uric acid Fig. 15.4 Types ofexcretory waste in different animals 1 5.4.1 Urinary System ofMan The urinary system or renal system is a system forremoving waste from the body. This system not only removes the toxins but also maintain the body's homeostasis regulating the body acid base balance by controlling the electrolytes and metabolites, blood pressure and blood pH. The organs associated in urinary system area pair of kidneys, ureters, a bladder and urethra. Kidneys are the blood purifier. These are paired, bean shaped stmctures located in abdominal cavity. Blood enters in to the kidney by renal arteries, both kidneys filter and remove waste substances from the blood and form filtrate. That filtrate ultimately becomes urine which ñows down through the ureter. Uzetez Ureters are 25 to 30 cm long tubes connected anteriorly with kidneys by wide opening called renal pelvis posteriorly they become narrow and extended downward to join urinary bladder. Ureters drain urine in to the urinary bladder where it is temporarily stored. The wall of the bladder is thick Fig. 15.5 Urinary system of man muscular and strong enough to hold half liter of urine in adults for some time then it is excreted out from the body by a connected muscular thin tube called urethra. Urethra has valves called sphincters that control the flow of urine. The internal urethral sphincter regulates involuntary control of urine flow from the bladder to the urethra, and the external urethral sphincter provides voluntary control of urine flow from the bladder to the urethra. 15,4. 1. Structure and Function of Kidney Kidneys are symmetrical, bean shaped reddish brown structures located just below the rib cage, one on each side of the vertebral column between the 12th thoracic and 3'd lumber vertebrae. Kidneys positioned retroperitoneal in the abdominal cavity. These are 4 to5 inches long almost size of the fist. The right kidney is located slightly below theleft kidney providing space toadjust liver. Left kidney isslightly larger and closer to the heart. Adlpoae t1ssue 1zz zeaa1 s1aus Fig.15.b L.S of Human kidney Externally kidneys are s+irrounded by a layer tough connective tissue called renal fascia behind that another fatty layer is present and the inner most layer covers the kidneys called renal capsule. Kidneys are laterally convex laterally and the medial side is deeply concave this medial depression hollow from inside called renal sinus. In the medial depression a small convex region is called hilum is present which has hollow sinus inside and serve as an important location for the entrance of blood vessels, nerves, lymphatic vessels and the ureter into the kidney.  Kidneys have two distinct regions internally: outer cortex and inner medulla. Renal cortex is surrounded by renal capsule which provides shape to the kidney. Renal cortex contains arteriole and venule and the cells called nephron. This isouter thin region then the medulla and produces an important hormone erythropoietin necessary forthe synthesis of RBC's. Renal medulla iscomposed ofcompact seven to eighteen conical shaped masses oftissues called renal pyramids. The spaces in between pyramids arecalled renal columns. Medulla regions mostly contain the loop of Henle part of nephron and the collecting ducts. Urine enters the collecting duct and then flow towards the hilum and then collected by pelvis and ureter to remove from the body. 1$. 3.2. STRUCTURE OF NEPHRON Both kidneys are consisted of millions of functional units called nephrons. These nephrons are about one million in each kidney and mainly perform filtration of blood. There are two types of nephrons present in the kidneys. The rr»amo convoluted Bowman’g tubule juxta medullary nephrons have capsule Distal Convoluted tubule longer loop of Henle penetrates Rffereztt deep inside the medulla and arteriole cortical nephrons with shorter G1ozaeru1ua loop of Henle restricts only in cortex region. Ltuxta medullary Afferent artero1e nephron consists of a renal _ corpuscle and a renal tubule. Peritubular Reaa1—s Renal corpuscle consists arterp ' I x apillarieh of a dense cluster of blood Read I r CoHecting, capillaries network called eeln duct ILO glomerulus surrounded by Descezzdlzzg ABcetzd?zsg thin-walled covering called Bowman's capsule or loop a:tbe zzepbrozz glomerular capsule and both are Fig. 15.7 Structure of Nephron collectively called malpighian body. Glomerulus isthe ball like stmcture which arises from afferent arterioles. High volume and pressure of blood facilitates the ultra- filtration in this region. Glomerular capillaries have pores of about 70 nm in diameter which prevents the large molecules and blood cells to pass through it. Glomerulus have specialized Podocyte cells that are wrapped around blood capillaries. These cells have small slits like opening that play an active role in preventing plasma proteins from entering the urinary ultrafiltrate. All the glomerulus capillaries fuse to form efferent arteriole, which exit the malpighian body. efferent arterioles, due to difference in diameter between these arterioles, high pressure in glomemlus than other capillaries elsewhere. The efferent arterioles extended down and forming a network of capillaries called peritubular capillaries that surround the both PCT and DCT. It provides nutrients and oxygen tothe renal cortex. It moves downward along with loop of henle give branches which are laterally connected with the capillaries of renal vein or venule in the region of medulla. This complex network capillaries over the loop of henle called vasa recta. After passing through the vasa recta blood flow through peritubular capillaries system and enters in to the renal vein to join venous circulation and leaves the kidney. 15.3. 8. Flanetions of the kidney Kidneys are very important Table 15.1 homeostatic organs. It filters our Coniposition of plasma and urine blood and excretes waste and extra fluid from our body by urine. Subatanee plasma urżne Kidneys also work as an endocrine Water 90 95 organ and secrete some vital Protein 8 0 hormones like renin and Glucose 0.1 0 erythropoietin. Renin maintains Urea 0.03 2 the blood pressure while erythropoietin is involved in red Uric acid 0.004 0.05 blood cells production. Kidney Ammonia 0.0001 0.04 produces an active form of vitamin Creatinine 0.001 0.075 D3 which helps to absorb calcium Na* 0.32 0.35 and phosphorus in our bones. K+ 0.02 0.15 These important minerals keep Cl 0.37 0.60 PO4° 3 0.009 0.27 bones strong. Kidneys balance the pH of our body by making changes SO‹-* 0.002 0.18 and adjusting amount of bicarbonate HCO° from the urine back totheblood and by secretion of H* ions into the urine. Kidney regulates the water balance by producing dilute and concentrated urine according to the external environmental changes. The process of producing urine occurs in three stages glomerular filtration, selective reabsorption, and tubular secretion. a} Glomerular filtration Urine is the ultimate kidney product and based upon waste removed from the blood with addition of some other fluids and ions. This process is initiated in the glomerulus when blood is filtered out under hydrostatic pressure leaving the small molecules of waste and other compounds as glomerular filtrate this process is called ultra- filtration. Filtrate primarily includes water, electrolytes, some amino acids, bicarbonates and nitrogenous wastes lihe urea, uric acid and creatinine. Glomerular filtration rate (GFR) is directly proportional to the hydrostatic pressure exerted in itswall. This pressure isincreased due to the difference in diameter ofboth afferent and efferent arterioles as mention earlier. mdney receives 180 liters of blood by circulation in 24 hours and after filtration it produces 2. 5 liters urine in normal climatic conditions. GFR usually remains constant by autoregulation however it may change depending upon thefluid intake or its variable amount inthebody. bJ Selective reabsorption The composition of glomerular filtrate and the urine is different it means that the fluid contents become change while passing through the renal tubules including PCT, loop of henle and DCT in nephron. For example, glucose ifpresent in the filtrate but absent in the urine y ofa healthy person. The amount ofurea and uric acid present more in urine than the filtrate. These changes are the outcome of selective reabsorption and the tubular secretion. Selective reabsorption isthe process whereby certain molecules after being filtered out of the capillaries along with nitrogenous waste products (i.e., urea) and water in the glomerulus, are reabsorbed from the filtrate as they pass through the nephron and return back totheblood circulation. Most of the selective reabsorption of molecules takes place in proximal convoluted tubule {PCT). Water (about 67%), Na+ and K* variable quantities of Cl (about 50%), Ca2+, Mg2+, and HPOo ions, important nutrients like glucose (100%), amino acids, vitamins and other organic substances are reabsorbed in PCT and given back to the blood circulation. Water isabsorbed passively while glucose and sodium are absorbed actively. Na+ drags the other negatively charged ions due to opposite charge interaction. Hormone aldosterone facilitates the sodium and ADH facilitates the water reabsorption. cJ Tubular secretion In this process certain substances moves intothefiltrate of PCT and DCT from blood plasma. This includes waste that escape during ultra-filtration and remained in the blood. These substances are absorbed actively and include urea, creatinine, hydrogen ions, potassium ions, some hormones and drugs if present. Tubular secretion mostly performed by proximal convoluted tubule (PCT) but some oftheK+ arealso secreted from DCT and collecting duct due to reciprocal exchange ofNa+ with K+. it adjust the pH of urine. dJ Counter current mechanism The counter current mechanism isbiological processes intend to allow maximum exchange of molecules between two fluids of different concentration which are moving in opposite directions. This mechanism involves loop of henle and the environment ofmedulla. In medulla region of the kidney, the ascending limb of loop of henle is permeable to Na+, K+ and Cl ions while impermeable to water. The descending limb of loop of henle ispermeable to water. Ascending limb cells have specialized ionic co-transporter protein, each allow one Na+ with one K+ and two Cl hence allow lotof ions to move out from the entire limb. when these ions are actively reabsorbed from the ascending limb and accumulated in medulla, it makes medulla environment hypertonic. This movement ofions isalso facilitated by a steroid-based hormone called aldosterone secreted from the cortex region of adrenal gland. Movement ofwater molecules isfacilitated by anti-diuretic hormone |ADH} secreted from posterior lobe of pituitary gland. Another compound that increases the osmotic gradient in inner medulla isthe Urea, it enters in the medulla from the collecting duct and along with other ions, helps the reabsorption of water. This process is called counter current multiplier. Now there is another counter current mechanism performed in between nephron loop of Henle and the peritubular capillaries or vasa recta. The loop of Henle is surrounded by peritubular capillaries containing blood. These capillaries are permeable to both water and ions so due to high ionic concentration in the interstitium, water is diffusing out and solutes diffuse inside the capillaries that travel alongside the descending limb, if this blood iscarried away it destroy the medullary concentration gradients. Therefore, to counter act this effect the peritubular capillaries alongside of ascending limb releases the extra solutes which diffuse back in to the medulla hence maintaining the concentration gradient inside medulla and making blood more dilute. This process of exchange of gradient in vasa reeta or peritubular capillaries is called counter current exchange. So,the water is secreted then reabsorbed in to the system. Solutes are reabsorbed then secreted in to the medulla. Normally the blood flow is slower in peritubular capillaries or vasa recta to allow time forpassive diffusion. 15. DISORDERS 0£ URINARY TRACT Urinary tract infections are the infections in organs associated with urinary system. These infections are usually caused by bacteria and viruses that invade or enter through anus or urethral opening or by other means. The site of infections could be any part of the urinary system like kidneys, bladder ureters and urethra The most common urinary tract infections among others are Pyelonephritis, Cystitis and Urethritis. Xaane o£tbe Cause disease if bacterium reaches in the ludneys it Pye1onephzftis E. coli brings nausea, vomiting, back pain, high fever with cold Feeling the frequent or urgent need to E. coli, urinate, Difficulty starting urination, Chlamydia, Urethritis Pain during sex, Discharge from the Neisseria urethral opening or vagina gonorrhea A strong urge to urinate, Pain or a burning feeling when urinating, Passing frequent, small amounts of urine, Blood in the urine, Passing Cystitis E. coli cloudy or strong-smelling frequent urine, Pelvic discomfort,A feeling of pressure in the area below your belly button (abdomen), Low-grade fever. 15. o.2 Kidney Stones Urine contains many dissolved mineral and salts that form different compounds. The components of these compounds include calcium, sodium, potassium, oxalates, uric acid and phosphate. Increased level of calcium in urine is called hypercalciuria and high level of oxalates in urine is called hyperoxaluria. When these components in the urine get too high or urine becomes tooacidic or basic, they combine to form crystals. The crystals progressively grow and become detectable stones in months or a year. This presence of stones in the kidney iscalled Nephrolithiasis or Urolithiasis and the inflammation in kidneys due to irritation of kidney stones is called Lithonephritis. %dney stones hinder the flow of urine and cause severe pain in the back. Calcium onalate isthe most common type of crystals to form 80 % ofkidney stones. Other5 to 10% ofless common type of kidney formed by calcium phosphate or uric acid. Some stones are formed by magnesium ammonium phosphate {struvite) in alkaline urine due to bacterial activity. These stones are about 10 percent and called struvite or infectious stones. Less than1 percent of urines stones are formed by an amino acid cystine. Cystine stones are usually formed in childhood. this procedure one catheter is placed in the bladder to drain urine out of the body then another catheter is inserted into the ureter to track down thestone by attached visual device. Once thestone is detected it is emshed and nephroscope grasper is used topull out the pieces of stone from the kidney. If the stones are too many or large then laparoscopic pyelolithotomy procedure is used inwhich kidneys are cut open toremove stones physically. 15. 4.2 Kidney Failure Kidney failure is the condition in which kidneys fail to extract nitrogenous waste products and perform osmoregulatory activity in the body. In this medical condition more than 85% ofthe both kidneys are affected. Kidney failure is classified as acute and chronic. Acute kidney failure is concerned with the suddenly loss of filtering abilities of the kidney. This condition develops in a few days particularly in those who are already having renal abnormalities and hospitalized. The diseases that could cause thekidney failure are blood loss due to injury, heart attack, liver failure, severe allergic condition, and sudden dehydration due to sweating or excessive urination, urinary tract obstmction due to stones or any infection. Chronic kidney disease involves a gradual loss of kidney function. Initially this disease shows no symptoms in the body but periodic blood or urine test indicate the problem. Itssymptom includes fatigue, short breath, swollen hands orfeet, blood in urine. The causes are hypertension, hyperglycemia, high cholesterol, cyst develop inside the kidney, kidney stones and inflammation. 15. 4.3. Dialysis Dialysis is a medical procedure to separate unwanted and toxic substances from the blood by artificial means. It is performed when kidneys are failed to remove waste from the blood body feels unrest particularly in breathing and later on non-adjusted biochemical components cause serious damages tothebody like dementia or heart failure. There are different types of dialysis applied on patient depending upon the need and intensity of disorder, these are hemodialysis, continuous renal replacement therapy {CRRTJ and peritoneal dialysis.  The hemodialysis is performed by a machine regarded as artificial kidney. This artificial kidney contains a number oftubules with a semipermeable lining suspended ina tank filled with a dialyzing fluid. This fluid has the same osmotic pressure as blood except it lachs nitrogenous waste. To begin the procedure a surgeon, make a small incision to connect artery with a vein by a graft i.e., a small plastic tube that connect the both artery and vein also called a fistula. When thecircuit is completed two needles are inserted in to the AV fistula. The one needle is connected to the artery and at the other end it is connected tothe dialysis device where blood iscollected from patient forfiltration. During this process the waste product from the blood passing into the dialyzing fluid by diffusion. The purified blood ispumped back into the vein of the patient which is connected to other end of the dialysis device. This is similar to the function of the kidney but it is different since there is no reabsorption involved. Hemodialysis is normally performed as 4-hour treatment,3 times a weeh. The complications in this process may include the risks of blood infection, thrombosis and internal bleeding due to the added anticoagulant. Fig. 15. 12 Haemodialysis  Continuous renal replacement therapy {CRRTJ isthe same class as hemodialysis. It is used forthe patients who are in critical condition and it is design for the patients who are unable to tolerate the repeated procedures of hemo. or peritoneal dialysis. This procedure ismnning continuously 24 hours a day once started. In peritoneal dialysis, abdominal cavity is used to filter blood. This procedure starts when doctor makes an incision at the lower abdominal cavity to implant or pass catheter. Which issoft tube that allows dialysate to pour in to and out of the abdominal cavity. Abdominal cavity is internally lined with the peritoneum which serves as the natural filtering membrane. When thedialysate is poured inside the abdominal cavity it pulls toxins from the blood that pass-through peritoneum membrane from its high concentration to the low concentration. The fluid remains inthe body ofseveral hours allowing exchange and equilibrium of ionic components with the blood mnning in the underlying vessels before being discarded. The dialysate is removed when it appears saturated and this process isrepeated again if needed. Peritoneal dialysis can be repeated4 to5 times a day. It is less effective than hemodialysis but because it can be performed for longer periods of time. Peritoneal dialysis offers more flexibility, is better tolerated by patient, and less expensive but it is more often complicated with abdominal infections. Pezltoaeal Pezltozzeal Perztoaeuzo oralztage @eratoaeuzo Dzaiaage it Catfzetez‘ ’ Catfzetez Fig.1 5. 13 Peritoneal dialysis 15.4. 4. Kidney Transplant Itidney transplant is the major surgical treatment of kidney failure disorder. In this procedure, a healthy kidney from a living or deceased donor isacquired and isplaced in the lower belly on the front side of the body. The diseased kidneys are usually left in place. Kidney transplant is done when thekidneys have lost about 90% of their ability to function normally due to some serious disorders like high blood sugar level and uncontrolled high blood pressure, kidney stones and polycystic kidney disease etc. Donor Recipient k1daey Fig.15.14 Kidney Transplant Principles of kidney transplant Kidney transplant requires the same matching blood group and biochemical components with the kidney donor and recipient. The compatibility is necessary without it, transplant cannot be done. The resistance against the implanted kidney by the immune system particularly from human leucocytes antigen system (HLA) should be minimize at the level that body accept new kidneys. Problems associated with kidney transplant After transplants the Immunosuppressant drugs like Cyclosporine are administered. This would be therisk factor along with treatment because at first it must be given to stop the body from rejecting the new kidney and minimize the side effects but at the other end it may invite some other opportunistic infections to enter the body  due tosuppressed immune system. Kidney transplant surgery involves substantial complications like blood clots and bleeding, leaking from or blockage of the tube that links the kidney to the bladder (ureter}, different bacterial Infection, those infections or cancer that can be passed on from the donated kidney, Death, heart attack and stroke. Besides allcomplications studies reveal that people who have done their kidney transplant live better and longer than those who keep on dialysis. 15. THEBBIO&EGULATIOS Thermoregulation is a homeostatic mechanism that heeps the body temperature of an organism up to suitable limits independent of external environmental temperature. It is all about keeping the stability of thermal energy expense in the body. This stability of temperature isnecessary because if a person suffers with loss the body heat (i.e., hypothermia) in a very low external temperature then this condition may lead to low metabolic activities, cardiac arrest, brain damage and even death. Likewise, if the body temperature raises from 370C to 420C (i.e., hyperthermia) a person also suffers with many complications like fever, osmoregulatory imbalance, stroke or even death in rare cases. Temperature is the limiting factor for enzyme activities. Body metabolism depends upon theenzymes and change in 4 temperature affect the working of enzymes which disturbs the metabolic activities. 1 fi. 6. 1. Animals' Classification on the Basis of Thermoregulation Animals areclassified on the basis of their capability to maintain body by utilizing different heat sources. Those animals who derives temperature to warm their bodies from external sources are called ectotherms or poikilotherms. Since ectotherms rely on environmental heat sources, they can operate at economical metabolic rates. Ectotherms live in environment where in which temperatures are constant such as tropics or ocean therefore, they would rather prefer to get heat by behavioral means rather than the physiological activities. These animals include invertebrates, fishes, amphibians and reptiles. Animals who maintain a constant internal body temperature, usually within a narrow range of temperature are called endotherms or homeotherms. These animals regulate their own body temperature through internal metabolic processes. When external environment becomes cold or hot, they autonomically monitor these changes and maintain the body temperature up to normal range through physiological and behavioral strategies. These animals include birds and mammals. Some animals are called heterothermic animals. These animals can switch between homeotherms and endotherms. These changes in strategies typically occur on a daily basis or on an annual basis. These animals regulate body temperature usually as constant, but allows body temperature to fluctuate with the environment when inactive. Bats and hummingbirds go into what isknown astorpor and bears hibernate. Both are examples of heterothermy; where the internal temperature of the animal drops during specific perlods of time, usually when food is scarce 15.5.2. Thermoregmlaton in Humans Humans maintain their body temperature at suitable limit that is 370C. We are adapted some behavioral and physlological strategies to adjust thermogenesis in cold and hot environment. Thermoregulation is controlled by an important part of our brain called hypothalamus which isconsidered as the thermostat or set point for temperature. Hypothalamus detects changes of the body temperature by receptors located in different parts of the body and responds accordingly. dig.1 5.1 5 Vasoeoiistriction and Vasodilatioii  For example, if the surrounding environment becomes hot or a person do strenuous physical activity, the heat produced inside the body and raises body temperature above suitable limit this condition is called hyperthermia. That heat is transported to the blood which carries it near to the skin. When this elevated body temperature is detected by hypothalamus it neurologically activates the sweat glands to start secretion. As the skin perspires, the evaporating sweat take away thebody heat from the blood into the surrounding environment. This cooled blood isthen transported back through thebody toprevent the body temperature from becoming toohigh. The blood vessels near to skin dilate in hot condition and facilitate the maximum transfer of heat away from inside the body. This dilation of blood vessels is called vasodilation. Thinning ofhypodermis lowers the perspiration and this condition may lead to heat stroke and exhaustion. Humans canalso transfer heat by conduction and convection as well. Conduction means heat transfer through some physical interaction for example prickly heat powder or ice pack makes a cooling effect on skin. Convection means transfer of body heat by movement ofairorwater molecules across the skin. When thebody experiences cold environment and body temperature tends to decrease this condition is called hypothermia. To conserve body heat in hypothermia, perspiration reduces and blood vessels become narrow and carrying blood down to skin. This condition of blood vessels is caUed vasoconstriction. The subcutaneous fats become thick and become an insulating layer to conserve heat in the body. In hypothermia sometimes body shivers Syzzzpatbetlc activity and this involuntary pty (Vasocozzstrlctloa) action of muscles generate heat to warm the body. The vasoconstriction Epidermis caused by hypothermia induces renal dysfunction Dezzol and cold diuresis due to Sweat _ Aztosñ eaous the decreased levels of glaad ADH. These decreased Veaule levels of antidiuretic uz: ri$. is. is hormone result in dilute urine. Thermoregulation throueh skin Homeostasis is process by which biological systems maintain stability while adjusting to the changing conditions. Feedback, in biology,a response withina system. There are two types of feedback mechanisms that counter act upon each other called positive and negative feedback. Fresh water and marine water animals adjust their osmotic internal environment according to the changing external environment primarily by excretion. Animals produce different types of excretory waste toregulate their internal homeostatic environment. Urinary system is not only used forremoving waste from the body, but also maintains the acid base balance of the body.  1. Encircle the correct choice i) A self-regulating process by which biological systems maintain stability while adjusting to the changing conditions called {a} Homeostasis (b) Osmoregulation (c) Excretion (d) Biological rhythms ii) Which does not maintain a stable, homeostatic condition rather it intensifies the change that is happening to the body. (a) Negative feedback (b} Positive feedback {c) Feed back system (d) Excretion iii) Fresh water organisms also have specialized cells located in their gills and in skin which actively extract Na+, Cl and Ca+ from external medium and excrete (H*) or basic (HCO3-) for acid base balance in the body fluids are called {a) Granulocyte (b) Lymphocyte (c) Ionocytes (d) podocyte ( iv) Renal cortex produces an important hormone necessary for the synthesis of RBC's (a) Erythropoietin (b) Leukopoietin (c) Thrombopoietin (d) Renin v) Glomerulus have specialized cells that are wrapped around blood capillaries that play an active role in preventing plasma proteins from entering the urinary ultrafiltrate called (a) Epithelial cells (b} Podocyte cells {c) Endothelial cells (dJ None ofthem vi) Tubules secretes ions such as hydrogen, potassium, and NH3 into the filtrate while reabsorbing the HCO3 from the filtrate are called {a) Distal convoluted tubule (b) Proximal convoluted tubule {c) Collecting duct (d) Loop ofHenle Vii) Glomerular filtration rate (GFR) is in which proportional to the hydrostatic pressure exerted in glomerulus wall (a) Indirectly proportional (b) Directly proportional {c) Same proportional (d) High proportional