10.1 (Osmoregulation 2)

What is osmoregulation?

The maintenance of proper water and solute balance in body fluid compartments.

What is ionoregulation?

The regulation of salt/ion concentrations in body fluids.

Where is intracellular fluid located?

Inside cells; contains the majority of body water.

What are extracellular fluids?

Fluids outside cells including plasma, lymph, interstitial fluid, and transcellular fluids.

What determines osmotic pressure?

The concentration of ions and solutes in body fluid compartments.

What are the main roles of the vertebrate kidney?

Volume regulation, solute concentration regulation, acid-base balance, and nitrogen waste removal.

What does volume regulation control?

Total body fluid amount and blood pressure.

What does acid-base balance involve?

Regulating pH by removing acids from the body.

What is a conformer?

An organism that allows its internal environment to change with external conditions.

What is a regulator?

An organism that maintains internal conditions despite external changes.

Are organisms perfect conformers or regulators?

No; most organisms exist somewhere between both strategies.

What are fenestrated capillaries?

Leaky capillaries with window-like openings that allow fluid and small solutes to pass.

What substances do NOT usually enter kidney filtrate?

Blood cells and very large molecules.

What is ultrafiltrate?

Fluid and small solutes filtered from blood into the nephron.

What is reclamation/reabsorption?

Moving needed substances from filtrate back into the blood.

Why does reclamation require energy?

Substances are often transported against their concentration gradient.

What is secretion?

Movement of toxins and nitrogen wastes from blood into filtrate.

How does the body control urine concentration?

By adjusting salt and water movement.

Why does water follow salt?

Water moves by osmosis toward higher solute concentration.

What is the glomerulus?

A bundle of fenestrated capillaries where blood filtration occurs.

What is Bowman's capsule?

The structure that surrounds the glomerulus and collects ultrafiltrate.

What does the afferent arteriole do?

Brings blood into the glomerulus.

What does the efferent arteriole do?

Carries blood away from the glomerulus.

What is the pathway of filtrate through the nephron?

Bowman's capsule → proximal tubule → distal tubule → collecting tubule.

What happens in the proximal tubule?

Most reclamation/reabsorption occurs.

What happens in the distal tubule?

Water and ion balance are adjusted.

What does the Loop of Henle do?

Adjusts osmolarity to improve water and salt regulation.

What does stenohaline mean?

An organism that tolerates only a narrow range of salinity.

What does euryhaline mean?

An organism that tolerates a wide range of salinity.

What problem do freshwater fish face?

Water enters their body and salts leave.

Why does water enter freshwater fish?

Their body fluids have more solutes than the surrounding freshwater.

How do freshwater fish remove excess water?

They produce large amounts of dilute urine.

How do freshwater fish regain salts?

They actively transport salts into the blood through the gills.

What is the goal of freshwater fish osmoregulation?

Replace lost salts while removing excess water.

What do branchial exchangers do?

Use gill transport systems to exchange ions.

What is an antiport system?

A transporter where ions move in opposite directions.

What problem do saltwater fish face?

Water leaves their body and excess salts enter.

Why does water leave marine fish?

Seawater has a higher salt concentration than their body fluids.

How do marine fish conserve water?

They drink seawater and produce very little urine.

How do marine fish remove excess salt?

Specialized chloride cells in their gills.

What are chloride cells?

Mitochondria-rich cells that actively pump chloride ions out.

Why do chloride cells have many mitochondria?

Active transport requires large amounts of ATP.

What is the main challenge of terrestrial osmoregulation?

Preventing water loss.

How do terrestrial animals lose water?

Evaporation through skin and respiratory surfaces.

What is keratin?

A vertebrate protein that waterproofs and protects external surfaces.

What are examples of keratin structures?

Hair, skin, nails, horns, scales, and beaks.

Why do amphibians have little keratin?

They rely on cutaneous respiration through their skin.

How do reptile scales reduce water loss?

They form a waterproof keratinized barrier.

How does mammalian skin prevent water loss?

Through cornified keratin layers and lipids.

What is nasal water recovery?

A system that conserves water during breathing.

What happens when air enters the nose?

It is warmed and moisturized before reaching the lungs.

What happens when air leaves the nose?

It cools and moisture condenses back onto nasal surfaces.

Why do desert animals have complex nasal conchae?

More surface area increases water recovery.

Where does nitrogen waste come from?

Breakdown of proteins and nucleic acids.

What is ammonia?

The first nitrogen waste product produced.

What are characteristics of ammonia?

Very toxic, water soluble, low energy cost.

Why is ammonia difficult for terrestrial animals?

It requires large amounts of water to remove safely.

What is urea?

A less toxic nitrogen waste product used by synapsids.

What is the advantage of urea?

It can be concentrated and stored in the bladder.

What is the disadvantage of urea?

It requires some energy to produce.

What is uric acid?

A non-toxic nitrogen waste product used by sauropsids.

What is the advantage of uric acid?

It allows nitrogen removal with very little water loss.

What is the disadvantage of uric acid?

It requires a lot of energy to produce.

What are salt glands?

Structures that remove excess salt while conserving water.

Why are salt glands useful?

They remove salt with almost no water loss.

How do nasal salt glands remove salt?

Salt is expelled through sneezing or head shaking.

How do sea turtles remove excess salt?

Through enlarged lacrimal glands near the eyes.