Controlling the Internal Environment Thermoregulation Osmoregulation Excretion Thermoregulation

Controlling the Internal Environment Thermoregulation Osmoregulation Excretion

Thermoregulation • Ectothermic • Endothermic • Poikilothermic • Homeothermic

Heat Exchange

Heat Exchange • Conduction - direct transfer of heat • Convection - transfer of heat by the movement of air or water across a surface • Radiation - emission of electromagnetic waves • Evaporation - loss of heat from changing a liquid into a gas

Body Temp vs. Ambient Temp

Thermoregulation Adjustments • Adjusting the rate of heat exchange – vasodilation/vasoconstiction – countercurrent heat exchange • Cooling by evaporation • Behavioral responses • Changing the rate of metabolic heat production

Endothermic Animals • Invertebrates – Large flying insects – Honeybees

Endothermic Animals • Fish – Bluefin tuna – Swordfish – Great white shark • Countercurrent heat exchange

Amphibians and Reptiles • Most are ectothermic – regulate temperature by behavior

Mammals and Birds • Contraction of muscles – moving – shivering • Nonshivering thermogenesis – triggered by hormones

Feedback Mechanisms • High body temperature – hypothalamus activates skin blood vessels to dilate and the sweat glands to produce sweat • Low body temperature – hypothalamus activates skin blood vessels to constrict and the skeletal muscles to shiver

Temperature Range Adjustments • Slow changes – acclimatization (enzymes and membranes) • Fast changes – heat-shock proteins

Metabolic Cycles • Torpor • Hibernation • Aestivation

Osmoregulation • Osmoconformers vs. Osmoregulators

Osmoregulation • Marine Fish – – hypoosmotic lose water to environment must excrete salt small amounts of urine • Freshwater Fish – hyperosmotic – gain water from environment – must take in salt – large amounts of urine

Functions of the Excretory System • • Filtration Reabsorption Secretion Excretion

Excretion of Nitrogenous Waste • Ammonia • Urea • Uric Acid

Invertebrate Structures • Protonephridia (flame cells) • network of closed tubules • used mostly for osmoregulation • found in platyhelminthes, some annelids, mollusk larvae

Invertebrate Structures • Open tubules surrounded by a nephrostome • Osmoregulation and excretion • Found in annelids

Invertebrate Structures • Malpighian Tubules • Open into the digestive tract • Osmoregulation and excretion • Insects and terrestrial arthropods

Excretory Systems Origins in Vertebrates • Pronephros, Mesonephros, Metanephros

Vertebrate Excretory Systems • Pronephros – adult hagfish, embryonic fish, amphibians, reptiles, birds, mammals • Mesonephros – adult lamprey, fish, amphibians, embryonic reptiles, birds, mammals • Metanephros – adult reptiles, birds, mammals

The Human Excretory System • • Kidneys Ureters Urinary Bladder Urethra

Blood Filtrate to Urine • Bowman’s Capsule and the Glomerulus – (filters the blood) • Proximal tubule – reabsorbed (Na. Cl, Potassium, Water, Nutrients) – secretes ( ammonia) – regulates (p. H)

Blood Filtrate to Urine • Loop of Henle – Descending loop • reabsorbed (water) – Ascending loop • reabsorbed (Na. Cl)

Blood Filtrate to Urine • Distal tubule – reabsorbed (Na. Cl, Water) – secrete (potassium) – regulate (p. H) • Collecting duct – reabsorbed (Na. Cl, Water, Urea)

Control of the Kidney • Antidiuretic hormone (ADH) – water reabsorption • Renin-angiotensinaldosterone system (RAAS) – water reabsorption • Atrialnatiuretic Factor (ANF) – inhibits the release of renin