Controlling the Internal Environment

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Controlling the Internal Environment

• Thermoregulation
• Osmoregulation
• Excretion

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Thermoregulation

• Ectothermic
• Endothermic

• Poikilothermic
• Homeothermic

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Heat Exchange
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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

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Body Temp vs. Ambient Temp
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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

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Endothermic Animals

• Invertebrates
• Large flying insects
• Honeybees

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Endothermic Animals

• Fish
• Bluefin tuna
• Swordfish
• Great white shark
• Countercurrent heat exchange

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Amphibians and Reptiles

• Most are ectothermic
• regulate temperature by behavior

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Mammals and Birds

• Contraction of muscles
• moving
• shivering
• Nonshivering thermogenesis
• triggered by hormones

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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

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Temperature Range Adjustments

• Slow changes
• acclimatization (enzymes and membranes)
• Fast changes
• heat-shock proteins

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Metabolic Cycles

• Torpor
• Hibernation
• Aestivation

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Osmoregulation

• Osmoconformers vs. Osmoregulators

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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

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Functions of the Excretory System

• Filtration
• Reabsorption
• Secretion
• Excretion

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Excretion of Nitrogenous Waste

• Ammonia
• Urea
• Uric Acid

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Invertebrate Structures

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

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Invertebrate Structures

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

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Invertebrate Structures

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

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Excretory SystemsOrigins in Vertebrates

• Pronephros, Mesonephros, Metanephros

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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

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The Human Excretory System

• Kidneys
• Ureters
• Urinary Bladder
• Urethra

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Blood Filtrate to Urine

• Bowmans Capsule and the Glomerulus
• (filters the blood)
• Proximal tubule
• reabsorbed (NaCl, Potassium, Water, Nutrients)
• secretes ( ammonia)
• regulates (pH)

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Blood Filtrate to Urine

• Loop of Henle
• Descending loop
• reabsorbed (water)
• Ascending loop
• reabsorbed (NaCl)

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Blood Filtrate to Urine

• Distal tubule
• reabsorbed (NaCl, Water)
• secrete (potassium)
• regulate (pH)
• Collecting duct
• reabsorbed (NaCl, Water, Urea)

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Control of the Kidney

• Antidiuretic hormone (ADH)
• water reabsorption
• Renin-angiotensin-aldosterone system (RAAS)
• water reabsorption
• Atrialnatiuretic Factor (ANF)
• inhibits the release of renin