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

Osmosis

• Define 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?

HYPOTHALAMUS

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?

Osmoregulation

• Water Loss

• 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