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 StructuresMetanephridia

• 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-angiotensin-

aldosterone system

(RAAS)

– water reabsorption

• Atrialnatiuretic

Factor (ANF)

– inhibits the release of

renin