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 (NaCl, Potassium, Water,
Nutrients)
– secretes ( ammonia)
– regulates (pH)
Blood Filtrate to Urine
• Loop of Henle
– Descending loop
• reabsorbed (water)
– Ascending loop
• reabsorbed (NaCl)
Blood Filtrate to Urine
• Distal tubule
– reabsorbed (NaCl, Water)
– secrete (potassium)
– regulate (pH)
• Collecting duct
– reabsorbed (NaCl, 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