1. Chapter 44 Controlling the Internal Environment http://www.funtrivia.com/playquiz/ quiz6309973beb0.html

2. Brief Overview to Body Temperature Regulation Each animal species has an optimal temperature range Thermoregulation: the maintenance of body temperature within a range that enables cells to function efficiently Animals exchange heat with their environment and need some way to replenish it This creates the difference between warm-blooded (endothermic) and cold- blooded (ectothermic) animals

3. Ectotherms Ectotherms are any animal whose body temperature is a result of their surroundings This is common in marine animals, retiles and amphibians in particular Breeding Ball, Cobra Mating, or Meerkats

4. Endotherms An endotherm is an organism that derives its internal temperature from its own metabolism Humans are endothermic and maintain a relatively constant internal body temperature Being endothermic solved many of the problems associated with living on land

5. Homeostasis By definition, homeostasis is the property of a system (open or closed) that regulates its internal environment so that it maintains a stable, constant condition Nerve cells that control thermoregulation and homeostasis are concentrated in the hypothalamus The hypothalamus is a part of the brain responsible for linking the nervous system to other systems like the endocrine system

6. Water Balance and Waste Disposal Our body has to maintain a balance between water uptake and water loss Because of our active aerobic metabolism, there are many by-products that can be toxic if accumulated To keep balance, our body must move solutes between body fluid and environment

7. Water Balance When getting rid of metabolic wastes, solutes must pass through transport epithelium This is the layer(s) of epithelial cells that regulate solute movement Most epithelial tissue is arranged in tubular networks These are very important to the urinary system

8. Waste Disposal The most toxic of all by-products are nitrogen-containing wastes (from breakdown of protein and nucleic acids) Most are form of ammonia Ammonia: excreted by marine animals Urea: mammals excrete this; 10,000 times less toxic than ammonia Uric acid: excreted by land snails, birds, and reptiles

9. Osmosis Def: the movement of water across a selectively permeable membrane Humans are osmoregulators: we must adjust internal solute concentration to match outside environment FYI- humans will die if they lose 12% of their body water

10. Excretory Systems These systems (namely the urinary) are vital to homeostasis because dispose of metabolic waste Urine is produced through two processes: filtration of body fluids & refinement of aqueous solution from filtration Filtration: blood is exposed to filtering device of selectively permeable membrane Water and small solutes in excretory system because of force of blood pressure; proteins and other large molecules too big to fit through membrane

11. Urine Production Reabsorpion is one of two mechanisms using active transport Selective transport of water and valuable solutes (glucose, salts, amino acids) from filtrate back into body fluids Filtration is nonselective-small molecules essestial to body are returned to fluids Secretion is another mechanism Involves adding of solutes (salt and toxins) from the body to the filtrate Once added to the filtrate, the solutes will pass with the urine out of the body

12. Kidneys & The Urinary System Kidneys are involved in excretion and osmoregulation (maintenance of solute concentration) Bean-shaped organs (10 cm long) Blood enters kidneys through renal artery and leaves through renal vein FYI- kidneys 1% of body weight, but receive 20% of blood pumped with EACH heartbeat

13. The Kidneys & Urinary System From the kidneys, the urine flows to ureters which connect to the urinary bladder leaves body through urethra There are two regions of the kidney: outer renal cortex and inner renal medulla Both filled with nephrons: functional unit of the kidneys Contains ball of capillaries (glomerulus) covered by Bowman’s capsule

14. Filtration Filtration occurs when blood pressure forces water, urea, salts, and solutes from the blood in the glomerulus into the Bowman’s capsule Capillaries called podocytes act as filter-permeable to water and small solutes but not large molecules If molecule is small enough to fit through the capillary wall, it will be filtered because filtration is nonselective

15. Nephrons and Components From the Bowman’s capsule, the filtrate goes through 3 regions of nephron: Proximal tubule Loop of Henle (had descending limb and ascending limb) Distal tubule Distal tubule empties into collecting duct (filtrate from nephrons)

16. Nephron The nephron and collecting duct are lined with transport epithelium to process filtrate 1100-2000 L of blood pass through kidneys/day, nephrons process 180 L of filtrate and create 1.5 L of urine Rest is absorbed into blood as mostly water

17. Secretion and Reabsorption Secretion involves both passive and active transport The controlled secretion of hydrogen ions from the interstitial fluid is responsible for maintaining pH Proximal and distal tubules involved in secretion Nearly all sugars, vitamins, and other organic nutrients are reabsorbed along with a large amount of water Proximal and distal tubules and loop of Henle contribute to reabsorption Selective reabsorption and secretion control concentrations of salt in body fluids

18. Flow From Filtrate to Urine Step 1: proximal tubule Maintains pH of body by controlling secretion of hydrogen ions Secretes ammonia and absorbs 90% of bicarbonate buffer Any drug/poison in liver is absorbed here Glucose, amino acids, K +, and NaCl are reabsorbed Water follows the movement of salt to interstitial fluid Step 2: descending limb of loop of Henle Permeable to water, not to salt/solutes Water leaves loop because it is hypotonic to the interstitial fluid around it NaCl concentration increases

19. Steps to Urine Formation Step 3: ascending limb of loop of Henle Permeable to salt, not water Two regions: thin segment (loop tip) and thick segment (leads to distal tubule) NaCl diffuses out in thin segment NaCl actively trasported out of thick segment Step 4: distal tubule Both secretion and reabsorption happen here Monitors amount of K + secreted into filtrate and amount of NaCl reabsorbed from filtrate Controls pH regulation

20. Urine Formation Step 5: collecting duct Carries the filtrate to renal pelvis and medulla, actively absorbs NaCl Permeable to water, not salt-loses more and more water to osmosis High concentration of urea diffuses out of duct These five steps are parts of each nephron, which are the components of the kidneys

21. Conserving Water by Kidney Action NaCl and urea are responsible for the osmotic gradient Each step in filtration in the nephron is meant to maintain conservation of water Proximal tubule (1): large amount of water and salt are reabsorbed-volume of filtrate decreases; molarity is still equal to blood

22. Water Conservation Descending limb of the loop of Henle (2): water leaves tubule by osmosis and NaCl concentration increases Salt concentration peaks at elbow of loop of Henle Ascending loop of Henle (3): salt concentration decreases because it is permeable to salt, not water Two limbs combined maintain osmotic balance and can affect each other’s chemical changes

23. Water Conservation The filtrate is hypotonic when it reaches the distal tubule NaCl concentration lowered in ascending limb From the cortex to medulla, the filtrate loses water by osmosis- concentration of urea increases Urine is isotonic in relation to interstitial fluid but hypertonic to blood and rest of body