1. Chapter 25: Control of Body Temperature and Water Balance

2. vocab
1. Thermoregulation: the maintenance of internal temperature within narrow limits
Aided by adaptations
Osmoregulation: the control of the gain and loss of water and solutes and the control of excretion
Excretion: the disposal of nitrogen containing wates

3. Endotherms vs ectotherms
Endoterms: they are warmed by heat generated by their own metabolism
Examples: birds and mammals
Ectotherms: they gain most of their heat from external sources
Examples: amphibians, lizards, many fishes and most invertebrates

4. How heat is gained or lost
1. conduction: the transfer of thermal motion (heat) between molecules of objects in direct contact
Convection: the transfer of heat by the movement of air
Radiation: the emission of electromagnetic waves
Evaporation: the loss of heat from the surface of a liquid that is losing some of its molecules as a gas

5. Metabolic Heat Production
In cold weather, hormonal changes tend to boost the metabolic rate of birds and mammals, increasing heat production
Shivering produces heat
Honeybees survive winters by clustering together and shivering in their hive

6. Insulation Hair, feathers, or fat layers
Most land mammals and birds react to the cold by raising their fur or feathers next to the warm skin
Aquatic animals are insulated by blubber

7. Circulatory adaptation
Heat loss can be altered by blood flow
In a bird or mammal, nerve signals surface blood vessels to constrict or dilate. When vessels constrict, less blood flows from the warm body core to the body surface reducing the rate of heat loss

8. Countercurrent heat exchange
Warm and cold blood flow in opposite directions in two adjacent blood vessels

9. Evaporative cooling and behavioral responses
Evaporative cooling can be increased by panting, sweating, or spreading saliva to body surfaces
Humans sweat
Dogs lose heat as moisture evaporates from their nostrils and mouth during panting
Migration
Lizards bask in the sun
Animals bathe
Dress for warmth

10. Nitrogen wastes Ammonia: aquatic animals
Most toxic of metabolic by-products
Too toxic to be stored in the body but is highly soluble in water
Soft bodied organisms (planaria) diffuse ammonia across it body surface
Fish diffuse it across their gills

11. Nitrogen wastes
Urea
Mammals, most amphibians, sharks and some bony fish
Highly soluble in water
Can be disposed of with relatively little water loss

12. Nitrogen waste Uric acid
Birds, many reptiles, insects, land snails and a few amphibians living in deserts
Avoid water loss problem completely
Relatively nontoxic
Largely insoluble in water
White material in bird droppings

13. Urinary System
Plays a central role in homeostasis, forming and excreting urine while regulating the amount of water and ions in the body fluids

14. Kidneys
Human body contains about 5 L of blood which repeatedly circulates through the capillaries in the kidneys everyday for about L per day
From this the kidneys extract about 180 L of filtrate (water, urea and valuable solutes)

15. Kidneys Blood to be filtered enters each kidney by the renal artery
Blood gets filtered and leaves each kidney by the renal vein

16. Kidneys continued
Urine leaves each kidney through the ureter and gets stored in the bladder.
The bladder then empties during urination
Urine leaves the body by the urethra

17. kidneys Renal cortex and renal medulla: 2 main regions of the kidneys
Each kidney contains about a million tiny units called nephrons

18. nephrons
Extracts a tiny amount of filtrate from the blood and then refines the filtrate into a much smaller quantity of urine
Each nephron starts and ends with in the kidney’s cortex
The receiving end of the nephron is the Bowman’s capsule and the other end is the collecting duct which carries urine to the renal pelvis

19. nephron
Bowman’s capsule envelops a ball of capillaries called the glomerulus
Glomerulus + Bowman’s Capsule=blood filtering unit of the nephron
Blood pressure forces water and solutes from the blood in the glomerular capillaries across the wall of the Bowman’s Capsule and into the nephron tubule- this process creates filtrate, leaving blood cells and large molecules

20. Nephrons continued Tubule has three sections Proximal tubule
Loop of henle (carries filtrate toward the medulla and back toward the cortex
Distal tubule (drains into a collect duct which receives filtrate from many nephrons)
From the collecting ducts the processed filtrate or urine passes into the renal pelvis and then into the ureter

21. 4 key processes of the Urinary System
filtration: water and all other molecules small enough to be forced through the capillary wall enter the nephron tubule from the glomeruls
Reabsorption: water and valuable solutes are returned to the blood stream from the filtrate
Secretion: substance in the blood are transported into the filtrate/ eliminates certain drugs and other toxic substances from the blood
Excretion: urine passes from the kidneys to the outside

22. Proximal and Distal tubules
Proximal tubule actively transports nutrients from the filtrate into the interstitial fluid to be reabsorbed into the capillaries
NaCl is reabsorbed by both the proximal and distal tubules and water follows by osmosis
Secretion of excess hydrogen and HCO3- occur here helping to regulate blood pH
Potassium concentration in the blood is regulated by secretion of excess potassium into the distal tubule
Drugs and poisons that were processed in the liver are secreted into the proximal tubule

23. Loop of Henle and collecting duct
Water reabsorption
Carries the filtrate deep into the medulla and then back to the cortex

24. Collecting duct Final refining of the filtrate
Determines how much salt is excreted in the urine
The nephron returns much of the water that filters into it from the blood-this water conservation is one of the kidneys major funcitons

25. ADH Antidiuretic hormone
Our kidneys maintain a balance between water and solutes in our body fliuds
When the solute concentration rises above a set point a control center in the brain increases the blood level of ADH