1. Regulating the Internal Environment
Chapter 44 Notes
Regulating the Internal Environment

2. Overview of Homeostasis
Homeostasis: the ability of animals to regulate their internal environment
- thermoregulation: maintaining internal temperature
- osmoregulation: regulation of the gain and loss of water
- excretion: removal of nitrogen-containing waste products

3. Overview of Homeostasis
Regulating and conforming are the two extremes in how animals cope with environmental fluctuations
- regulator: uses mechanisms of homeostasis to moderate internal change
- ex. endothermic animals

4. Overview of Homeostasis
- conformers: allow some internal conditions to vary with environmental changes
- ex. animals that live in stable environments

5. Overview of Homeostasis

6. Regulation of Body Temperature
Q10 effect: the rate of reactions increases by a factor of 2-3 for every 10oC temperature increase
Each animal has an optimal temperature range for enzymatic activity
- thermoregulation keeps the body temp within a range

7. Regulation of Body Temperature
Four physical processes account for heat gain or loss
- conduction: transfer of thermal motion between molecules in direct contact
- convection: transfer of heat by the movement of air or liquid past a surface

8. Regulation of Body Temperature
- radiation: the emission of electromagnetic waves by all objects warmer than absolute zero
- evaporation: removal of heat from the surface of a liquid that is losing some of its molecules as gas

9. Regulation of Body Temperature

10. Regulation of Body Temperature
Ectotherms have body temperatures close to environmental temperatures; endotherms can use metabolic heat to keep body temperature warmer than their surroundings
- endotherms have high levels of aerobic metabolism

11. Regulation of Body Temperature
- endotherms can be active in below freezing weather
- being endothermic is energetically expensive since animals need to produce a lot of heat to maintain their constant body temps. in cold weather

12. Regulation of Body Temperature

13. Water Balance and Waste Disposal
An animal’s nitrogenous wastes are correlated with its phylogeny and habitat
- when proteins and nucleic acids are broken down for energy and converted to fats and carbs, enzymes remove the amino group (NH2) and form ammonia (NH3)

14. Water Balance and Waste Disposal
Some animals will excrete ammonia directly, but many species will convert it to urea or uric acid
- less toxic but takes energy to convert
Ammonia
- found in aquatic animals
- diluted with water from the environment

15. Water Balance and Waste Disposal
Urea
- requires a moderate volume of water; excreted in high concentrations
- sharks, amphibians, and mammals
- produced in the liver and transported in blood
- requires energy to produce urea

16. Water Balance and Waste Disposal
Uric acid
- little water is excreted; water conserving animals
- insects, reptiles, birds
- precipitated as a solid

17. Excretory Systems
The urinary system is made-up of the kidneys, ureters, bladder, and urethra
- the nephron is the functional unit of the kidneys
- waste is filtered from the blood and collected as urine in each kidney

18. Excretory Systems

19. Excretory Systems
The kidney has two distinct regions, an outer renal cortex and an inner renal medulla.
The nephron consists of a single long tubule and a ball of capillaries called the glomerulus
- pressure causes water and solutes from the blood to filter into the capsule

20. Excretory Systems
The fluid, called filtrate, passes through three regions of the nephron: the proximal tubule, the loop of Henle, and the distal tubule
- fluids and solutes are returned to the capillaries that surround the nephron tubule

21. Excretory Systems

22. Excretory Systems The nephron has three functions:
- glomerular filtration of water and solutes out of the blood
- tubular reabsorption of water and molecules from the tubules back into the blood
- tubular secretion of waste products into the distal tubule

23. Excretory Systems
The purpose of the kidneys is to concentrate the filtrate in the kidneys to produce urine that has a higher osmolarity than that of blood
Bowman’s capsule  proximal convoluted tubule  descending loop of Henle  ascending loop of Henle  distal convoluted tubule  collecting duct

24. Excretory Systems
The nervous system and hormones regulate kidney function
Antidiuretic hormone (ADH): hormone primarily responsible for producing urine and regulating water balance
- an antidiuretic is any chemical that prevents excessive urine production

25. Excretory Systems
- hypothalamus contains osmoreceptors to detect the salt/water ratio in the blood and produces ADH when needed
- if the body is dehydrated, ADH is produced, and the urine volume decreases
- if the body has a high water concentration, the hormone secretion stops

26. Excretory Systems
Coffee, tea, and alcohol are diuretics, substances that increase urine flow
- alcohol inhibits ADH secretion and increases urine production
- without ADH, urine flow could be increased to 25 liters per day 