Regulating the Internal Environment Chapter 44 Notes Regulating the Internal Environment

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

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

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

Overview of Homeostasis

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

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

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

Regulation of Body Temperature

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

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

Regulation of Body Temperature

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)

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

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

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

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

Excretory Systems

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

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

Excretory Systems

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

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

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

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

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 