Osmoregulation Overview

What are the three major body fluids?

• Blood plasma

• Interstitial fluid

• Intracellular fluid

What is the main component of body fluids?

Water (H2O)

What is osoregulation?

Regulation of water levels and solute balance

How does osmoregulation work?

Organs regulate solute concentration to influence water movement

Osmolarity

solute concentration of a fluid

Osmosis

Diffusion of water across a semipermeable membrane

How does water move based on osmolarity?

Water moves from low to high osmolarity (hypo → hyper)

What is dialysis?

Solute movement from high to low concentration through a semipermeable membrane

What causes net water flow?

Any change in solute concentration in a compartment

What sources provide humans with their daily water intake?

from enviornment

• Drinking water

• Food

• Metabolic processes

What are major sources of water loss in humans?

Urine and feces

Why are osmoregulation and excretion closely tied?

Toxins must be diluted in water to be excreted

What system handles osmoregulation and excretion in humans?

Urinary system

(Kidneys, ureters, bladder, urethra)

What is the thirst mechanism controlled by?

hypothalamus, pituitary gland, and negative feedback loops

How does the thirst mechanism work (negative feedback loop)?

• Hypothalmus (detects increased osmolarity) →

• ADH from posterior pituitary →

• Kidneys reabsorb water

Nitrogenous wastes

waste from proteins/nucleic acids

• includes: ammonia, urea, urine acid

Why do animals convert ammonia?

To make it less toxic and save water

Ammonia

• High toxicity

• Low energy

• Needs a lot of water

Urea

• Medium toxicity

• Medium energy

• Medium water

Uric acid

• Low toxicity

• High energy

• Little water

What waste do humans excrete?

Urea (also helps create kidney osmotic gradients)

Four steps of urine formation

1. Filtration - blood into tubule

2. Reabsorption - valuable solutes returned to body

3. Secretion - toxins added to filtrate

4. Excretion - filtrate removed as urine

What is the kidney’s functional unit?

Nephron (tubule closely associated with capillaries)

What does the kidney regulate?

• Water balance (ECF volume)

• Blood pressure

• Blood pH

• Osmolarity

• Waste excretion

• RBC production

• Vitamin D metabolism

What are parts of the urinary system?

• Kidneys

• Ureters

• Bladder

• Urethra

Kidneys

filter blood

Ureters

transport urine

Bladder

Store urine

Urethra

expels urine