Biology 3.11 Oral Rehydration Therapy

What causes diarrhoea?

• Damage to epithelial cells lining the intestine.
• Loss of microvilli due to toxins.
• Excessive secretion of water due to toxins e.g. cholera toxin.

Excessive fluid is lost and/or insufficient fluid taken in = dehydration, may be fatal.

What is oral rehydration therapy?

Drinking water is ineffective for rehydrating diarrhoea patient because:

• Water not being absorbed in small intestine - sometimes e.g. cholera it is lost from the cells too.
• Drinking water doesn't replace lost electrolytes (ions) being lost from epithelial cells.

More than one type of carrier protein in cell-surface membranes of epithelial cells that absorbs sodium ions.

As sodium ions are absorbed, water potential of cells falls and water enters by osmosis.

Rehydration solution therefore needs:

• Water = rehydrates tissues.
• Sodium = replaces lost sodium ions, makes optimum use of sodium-glucose carrier proteins.
• Glucose = stimulates uptake of sodium ions, provides energy.
• Potassium =…