Osmoregulation
Maintaining homeostasis in solute concentrations

Water is better

Osmoregulation
• VIDEO!!!

Osmoregulation
• At a cellular level the balance of water supply and demand is critical.
• Why is it so important?

Osmoregulation
• Water dissolves solutes and is the medium in which everything happens
• Chemical reactions, transport of nutrients, gases and wastes.

Osmoregulation
• It is crucial that the solute concentration of the blood remains at a stable level.
• The solute concentration of the blood affects the diffusion of water across capillary walls and across cell membranes.

Osmoregulation
• For Example:
- A relatively low concentration of water in the blood and tissue fluid can affect the functioning of cells.
- This can be caused by excessive fluid loss or increased salt concentration.

Osmoregulation
• Mark Dorrity Story

• Define Osmosis
Osmosis
The movement of water across a semi permeable membrane from a place of
low solute concentration to a place of high solute concentration

Osmoregulation

Osmosis

Osmoregulation
• Where do you think these changes in concentration in the blood will be detected?

Osmoregulation

Osmoregulation
• If the hypothalamus detects that the concentration in the blood is too high. It releases a hormone that stimulates the pituitary gland to release ADH
• ADH in turn stimulates the kidney to absorb more water.

Osmoregulation

Osmoregulation
• The Loop of Henle is crucial for this process
• It can reabsorb more water if needed and be used to excrete salts.

Osmoregulation

Osmoregulation
• A thirst response is also initiated which forces animals to seek water.

Osmoregulation
• What are some ways in which water can be lost from the body?

• Water Loss
Osmoregulation
• Exhaling
• Sweating
• Urinating
• Faeces
• Tear Ducts

Osmoregulation
• Vertebrates have evolved effective ways in which to maintain the balance of water and solutes
• Can you think of any examples?

Osmoregulation
• Thirst response: Seeking water

Osmoregulation
• Waterproof (impermeable) outer layer [aka –
integument]: Reduce water loss – e.g. scales on reptiles, hair of mammals, feathers, keratin in skin, skin, hard exoskeleton.

Osmoregulation
• Reabsorption: Some animals reabsorb water from their faeces.

Osmoregulation
• Burrowing: The temperature is cooler underground so less water is lost. Burrows also have high humidity therefore water loss is reduced.

Osmoregulation
• Some animals stay underground fro extended periods of time while it is extremely dry.
• For example: the Cyclorana burrows deep and covers itself in a cocoon. The cocoon creates humidity.

Osmoregulation
• Changing waste products: Some animals excrete nitrogen in different ways to conserve water.

Osmoregulation
• Concentrating urine: By concentrating their urine animals can conserve water (e.g.
Notomys).

Osmoregulation
• Gets all its water from cellular respiration and conserves water by concentrating its urine.
• 1 gram of carbohydrates supplies 0.56 grams of water.

Osmoregulation
• Camels do a similar thing however they metabolise the fat in their hump to produce water.
• High tolerance to low water conditions.

Osmoregulation
• What do you do if you are surrounded by water?

Osmoregulation
• Some organisms don’t have to worry.
• These animals, mainly invertebrates, have the same internal solute concentration as their external environment.
• Meaning they are isotonic with the sea water.

Osmoregulation
• These animals are referred to as osmoconformers

Osmoregulation
• Other animals are not so lucky.
• Marine vertebrates have internal environments that are hypotonic to their surrounding environment.
• Their body fluids are less concentrated than the surrounding sea water.

Osmoregulation
• These animals must find ways in which to stabilise their internal environments.
• These animals are referred to as osmoregulators

Osmoregulation
• Water is lost by osmosis to the surrounding environment.
• To replace this water marine fish drink lots of sea water. However this also means they take in salts.
• They use secretory cells in the gills to get rid of excess salts.
• Production of concentrated urine also helps

Osmoregulation

Osmoregulation
• Fish in freshwater environments have an internal environment that is hypertonic to their surroundings
• Their internal environment is more concentrated than their surroundings
• This mean water continually moves in to their body.

Osmoregulation
• Freshwater fish produce large amounts of dilute urine.
• Actively absorb salts via cells in their gills
• Do not drink much water

Osmoregulation

REVIEW
• Describe the difference between osmoregulators and osmoconformers
• Describe the different methods of maintaining stable solute concentrations used by freshwater and
saltwater fish.
• List and describe the different adaptations animals use to conserve water.
• Describe why the kidney is so important in osmoregulation