1.  Chapter 44 ~ Regulating the Internal Environment

2. Homeostasis  Maintaining internal stability ThermoregulationThermoregulation OsmoregulationOsmoregulation  Negative feedback  Positive Feedback

3. Homeostasis: regulation of internal environment  Thermoregulation internal temperature  Osmoregulation solute and water balance  Excretion nitrogen containing waste

4. I. Thermoregulation: Regulation of Body Temperature  4 physical processes account for heat gain or loss.

5.  Conduction~transfer of heat between molecules of body and environment.  Convection~transfer of heat as water/air move across body surface (perspiration)  Breezes.  Radiation~transfer of heat produced by organisms. Animal warmed by heat radiating from sun.  Evaporation~loss of heat from liquid to gas.  Sweat; when relativehumidity is less than 100%

6.  Ectothermic:  Body temp varies with environment.  determined by environment.  Most invertebrates, most fish, reptiles, amphibians  Basking behavior  Endothermic:  Maintain constant internal temp  via its own metabolism  To retain heat, blood shunted away from surface-into deeper veins (vital organs protected).  Piloerection: birds & mammals- fluff feathers / body hair

7.  Surviving high temperatures often more difficult than cold.  High heat—destroys enzymes  Cold, only slows them down-or temporarily deactivates them.

8. Regulation during environmental extremes  Torpor~ low activity; decrease in metabolic rate.  Conserves energy  1- Hibernation long term or winter torpor (winter cold and food scarcity); bears, squirrels  2- Estivation short term or summer torpor.  (high temperatures and water scarcity); fish, amphibians, reptiles  Both often triggered by length of daylight

9. .  Daily torpor Some mammals and birdsSome mammals and birds Adaptation to feeding patternsAdaptation to feeding patterns Daily cycle of torpor and activity—biological clockDaily cycle of torpor and activity—biological clock

10. Water balance and waste disposal  Osmoregulation: Management of the body’s water content and solute composition.  Main goal-manage composition of interstitial fluid.  Vertebrate kidneys  Transport epithelium

11. Osmoregulation and Excretion  Regulate water and ions in the body  Removal of waste products  Closely related to one another

12. Nitrogenous wastes  Breakdown products of proteins and nucleic acids  Deamination-remove amino group from amino acids. ammonia is formed-very toxic ammonia is formed-very toxic  Type of N. waste depends on habitat & evolutionary history.

13. 3 Types of Nitrogenous wastes  1. Ammonia: most aquatic animals, many fish. Requires large amounts of water.most aquatic animals, many fish. Requires large amounts of water.  2. Urea:  mammals, most amphibians, sharks, bony fish (in liver; combo of NH 3 and CO 2 ). excreted as semi-dry paste. Low toxicity, but energy demanding Low toxicity, but energy demanding  3. Uric acid: birds, insects, reptiles, land snails Low toxicity paste; largely insoluble in water; most energy demanding.

14. Balancing osmotic gain and loss of water: Osmoregulators  Osmoconformer: no active adjustment of internal osmolarity (sharks, rays); isoosmotic to environment  Osmoregulator: adjust internal osmolarity (freshwater, marine mammals, terrestrial) Stenohaline animal= cannot survive wide fluctuations in external osmolarity (steno=narrow); Euryhaline-survive wide fluctuaions; salmon

15. Marine environment  Environment is hypertonic  Osmoconformers such as sharks, rays maintain their hypoosmotic environment by retaining urea in blood and body fluids  Sharks also pump salt out through anal gland.

16. Marine --Osmoregulators  Such as bony fish, secrete salt through gills Enables them to drink salty water through mouth.Enables them to drink salty water through mouth.  Marine birds-salt glands near eyes  Marine mammals-excrete salt through kidneys

17. Freshwater  Environment is hypotonic Water enters by osmosis, ions diffuse out.Water enters by osmosis, ions diffuse out. Getting rid of nitrogen wastes not a problemGetting rid of nitrogen wastes not a problem SomeSome

18.  Freshwater fishes (hyperosmotic)- gains water, loses; excretes large amounts of urine & salt vs.  marine fishes (hypoosmotic)- loses water, gains salt; drinks large amount of saltwater; concentrated urine

19. Sharks—special case Low internal salt concentration, so salt diffuses in (gills). Kidneys—urea and and rectal gland to secrete salt Also Retain urea in body fluids

20. Excretory Systems  Production of urine by 2 steps:  Production of urine by 2 steps:  1. Filtration (nonselective)  1. Filtration (nonselective)  2. Reabsorption (secretion of solutes)  Protonephridia - DEAD-END TUBES flatworms (“flame-bulb” systems) flatworms (“flame-bulb” systems)  Malpighian tubules ~ insects (tubes in digestive tract)  Kidneys ~ vertebrates

21. Osmoregulation in Terrestrial environments-the need to conserve water  Earthworm : nephridia remove nitrogenous wastes and excess salts.  Release through the nephridiopore.  Reclaim water and essential minerals

22. Arthropods  Malpighian Tubules collect waste from coelomic fluids; produce uric acid.  Excreted into gut— then reabsorption in hindgut—produce semi-dry waste

23.  Proximal tubule: secretion and reabsorption flatworms (“flame-bulb” systems)

24. Kidney Functional Units  Ureter: urine excretory duct  Urinary bladder: urine storage  Nephron: functional unit of kidney  Urethra: urine elimination tube  Renal artery/vein: kidney blood flow

25. Anatomy of Human Excretory System  Kidneys  Ureters  Urinary bladder  Urethra  Renal circuit ( renal arteries and veins)

26. The Kidney  Renal cortex (outer region)  Renal medulla (inner region)  Nephrons: form urine.  Passes from collecting ducts to the renal pelvis; empties into ureters; they conduct to urinary bladder, then to the urethra to void.

27. Nephron Structure  Proximal tubule: reabsorption of water, ions and ALL ORGANIC NUTRIENTS  Peritubular capillaries: from efferent arteriole; surround proximal & distal tubules  Loop of Henle: water & salt balance  Distal tubule: secretion & reabsorption  Collecting duct: carries filtrate to renal pelvis

28. Basic Nephron Function

29. Nephron Structure & Function 1.  Afferent arteriole: supplies blood to nephron from renal artery  Glomerulus: ball of capillaries  Bowman’s capsules: surround the glomerulus  Efferent arteriole: blood from glomerulus to the Proximate Tubule

30. The Excretory Process  1. Filtration: semi permeable membrane. Small molecules, water, urea pass (filtrate).  2. Reabsorption:Transport epithelium reclaims essential small molecules & returns them to the blood.  3. Secretion: Active Transport of ions, toxins into excretory tubules  4. Excretion: filtrate leaves excretory system and body as urine

31. Nephron Structure & Function 2.  Filtrate forms as Blood Pressure forces water and small solutes (from the blood) into the lumen of the Bowman’s Capsule, filtrate passes into the Proximal Tubule.  Proximal tubule:reabsorption of all organic nutrients, and some ions, water.  Loop of Henle: reabsorption of water and salt  Descnding: water reabsorption  Ascending: salt reabsorption  Distal tubule: secretion and reabsorption.  Collecting duct: reabsorbs water, salt

32. Nephron Control: hormones 1.  Antidiuretic hormone (ADH) Produced by Hypothalamus; secreted from posterior  Antidiuretic hormone (ADH) Produced by Hypothalamus; secreted from posterior pituitary gland.  controls water reabsorption.  Hypothalamus detects increased osmolarity-above a set point  (Due to Sweating/salty food)  ADH secreted from Pituitary-  This Increases the permeability of distal tubules and collecting ducts to water (H2O back to body).  Release of ADH inhibited by alcohol and coffee—(hangover)

33. 2. The renin-angiotension- aldosterone system; RAAS) 2. The renin-angiotension- aldosterone system; RAAS)  JGA-near afferent arteriole.   Response to low blood pressure or blood volume. From Reduced salt intake or blood loss.  Renin produced; Angiotension converted to Angiotension II  2 effects from AngiotensionII:  1) constriction of arterioles & proximal tubules reabsorb NaCl and H2O  2  2) stimulates adrenal glands to secrete Aldosterone— acts on distal tubules which .  increases absorption of Na+ and H2O.

34.  Juxtaglomerular apparatus (JGA) ~ reduced salt intake--->enzyme renin initiates conversion of angiotension (plasma protein) to angiotension II (peptide); increase blood pressure and blood volume by constricting capillaries  Atrial natriuretic factor (ANF) ~ walls of atria; inhibits release of renin, salt reabsorption, and aldosterone release

35. Hormonal Control

36. Water balance and waste disposal Ammonia: Most aquatic animals—need access to lots of water to dilute the ammonia Urea: produced in the liver Excreted by kidney Land animals, sharks, amphibians Less toxic; need less water Higher energy cost Uric Acid: insects, birds, reptiles. Semi-solid paste Highest energy cost

37. Kidney regulation: hormones  Antidiuretic hormone (ADH) ~ secretion increases permeability of distal tubules and collecting ducts to water (H2O back to body); inhibited by alcohol and coffee  Juxtaglomerular apparatus (JGA) ~ reduced salt intake--- >enzyme renin initiates conversion of angiotension (plasma protein) to angiotension II (peptide); increase blood pressure and blood volume by constricting capillaries  Angiotension II also stimulates adrenal glands to secrete aldosterone; acts on distal tubules to reabsorb more sodium, thereby increasing blood pressure (renin- angiotension-aldosterone system; RAAS)  Atrial natriuretic factor (ANF) ~ walls of atria; inhibits release of renin, salt reabsorption, and aldosterone release

38.  The kidney acts as a filter for blood, removing waste products from the body and helping regulate the levels of chemicals important for body function. The urine drains from the kidney into the bladder through a narrow tube called the ureter. When the bladder fills and there is an urge to urinate, the bladder empties through the urethra, a much wider tube than the urethra.  In some people, the urine chemicals crystallize and form the beginning, or a nidus, of a kidney stone. These stones are very tiny when they form, smaller than a grain of sand, but gradually they can grow to a quarter inch or larger. The size of the stone doesn't matter as much as where it is located.  When the stone sits in the kidney, it rarely causes problems, but should it fall into the ureter, it acts like a dam. The kidney continues to function and make urine, which backs up behind the stone, stretching the kidney. This pressure build up causes the pain of a kidney stone, but it also helps push the stone along the course of the ureter. When the stone enters the bladder, the obstruction in the ureter is relieved and the symptoms of a kidney stone are resolved.

39.  Kidney Stones Causes  There is no consensus as to why kidney stones form.  Heredity: Some people are more susceptible to forming kidney stones, and heredity certainly plays a role. The majority of kidney stones are made of calcium, and hypercalciuria (high levels of calcium in the urine), is a risk factor. The predisposition to high levels of calcium in the urine may be passed on from generation to generation. Some rare hereditary diseases also predispose some people to form kidney stones. Examples include people with renal tubular acidosis and people with problems metabolizing a variety of chemicals including cystine (an amino acid), oxalate, (a type of salt), and uric acid (as in gout). gout  Geographical location: There is also a geographic predisposition in some people who form kidney stones. There are regional "stone belts," with people living in the Southern United States, having an increased risk. This is likely because of the hot climate, since these people can get dehydrated, and their urine becomes more concentrated, allowing chemicals to come in closer contact and begin forming the nidus of a stone. dehydrated  Diet: Diet may or may not be an issue. If a person is susceptible to forming stones, then foods high in calcium may increase the risk, however if a person isn't susceptible to forming stones, nothing in the diet will change that risk.  OTC products: People taking diuretics (or "water pills") and those who consume excess calcium-containing antacids can increase the amount of calcium in their urine and increase their risk of forming stones. Patients with HIV who take the medication indinavir (Crixivan) can form indinavir stones. HIV indinavirHIV indinavir

42.  Large amounts of water -- approximately 178 liters per day -- are reabsorbed by osmosis from the proximal tubules. In other words, nearly 99% of the 180 liters of water that leave the blood each day by glomerular filtration returns to the blood from the proximal tubule through the process of reabsorption.  The nutrient glucose is entirely reabsorbed from the proximal tubules. it is actively transported out of them into the peritubular capillary blood. None of this valuable nutrient is wasted by being lost in the urine. (An exception to this occurs in a person who suffers from diabetes mellitus, where the urine contains more glucose than the kidneys are able to reabsorb.)  Sodium ions (Na+) and other ions are only partially reabsorbed from the renal tubules back into the blood. For the most part, sodium ions are actively transported back into blood from the tubular fluid. The amount of sodium reabsorbed varies from time to time; it depends largely on salt intake. As stated earlier, sodium is a major component of table salt (known chemically as sodium chloride). As a person increases the amount of salt intake, that person's kidneys decrease the amount of sodium reabsorption back into the blood. Therefore, the amount of salt excreted in the urine increases. The process works the other way as well. The less the salt intake, the greater the amount of sodium reabsorption back into the blood, and the amount of salt excreted in the urine decreases.

43.  Secretion is the process by which substances move into the distal and collecting tubules from blood in the capillaries around these tubules. (See Figure 4.) in this respect, secretion is reabsorption in reverse. Whereas reabsorption moves substances out of the tubules into the blood, secretion moves substances out of the blood into the tubules. Substances secreted are hydrogen ions (H+), potassium ions (K+), ammonia (NH3), and certain drugs. Kidney tubule secretion plays a crucial role in maintaining the body's acid/base balance.  In summary, three processes occurring in successive portions of the nephron accomplish the function of urine formation (Figure 4):  Filtration of water and dissolved substances out of the blood in the glomeruli into Bowman's capsule.  Reabsorption of water and dissolved substances out of the kidney tubules back into the blood. (Note that this process prevents substances needed by the body from being lost in the urine.)  Secretion of hydrogen ions (H+), potassium ions (K+), ammonia (NH3), and certain drugs out of the blood into the kidney tubules.  Control of Urine Volume  The body has ways to control both the amount and the composition of the urine it excretes. It does this mainly by controlling the amount of water and dissolved substances reabsorbed out of the tubules and into the blood. One of the mechanisms that the body uses to control such things is through the action of hormones, chemical messengers that travel through the blood system acting as regulators of many of the body's internal activities. (Hormones are secreted by specialized glands that form the endocrine system.) For example, the hormone ADH (antidiuretic hormone), which is secreted by the pituitary gland, tends to decrease the amount of urine by making distal and collecting tubules permeable to water. If no ADH is present, both distal and collecting tubules are practically impermeable to water, and little or no water is reabsorbed from them. When ADH is present in the blood, distal and collecting tubules are permeable to water and water is reabsorbed from them. As a result, water moves from the tubules back into the blood, and, therefore, more water is retained. For this reason, ADH is accurately described as the "water-retaining hormone." You might also think of it as the "urine-decreasing hormone." The hormone aldosterone, secreted by the adrenal cortex gland located at the top of each kidney, plays an important part in controlling the kidney tubules' reabsorption of salt, the most abundant electrolyte in the blood. (Aldosterone is also responsible for the regulation of other electrolytes as well, particularly potassium.) Primarily, aldosterone stimulates the tubules to reabsorb sodium salts at a faster rate. This means that in the presence of aldosterone, the salt moves more rapidly out of the kidney tubules back into the blood. Secondarily, aldosterone tends also to increase tubular water reabsorption (that is, water tends to flow out of the kidney tubules back into the blood). The term "salt- and water-retaining hormone" therefore is a descriptive nickname for aldosterone. The kidney tubule regulation of salt and water is the most important factor in determining urine volume.  Urine volume control is influenced by many factors and the precise regulation of urine volume is important and essential for many different reasons. Ultimately, the body's main requirement is to maintain a balance of fluids and a balance of body chemistry. From earlier in this document, you know that fluid volumes are affected by space flight. Overall fluid volume is decreased in microgravity. It is important to find out how microgravity affects the regulatory systems that control the fluid volumes and electrolyte concentrations.