Water and Alcohol Flashcards
Water
Water in the body
- essential nutrient
- comprises 50-70% of the body weight
Water
Functions of Water
- Metabolic processes
- Universal solvent for minerals, vitamins, amino acids, glucose and others
- Body temperature regulation
- Water absorbs excess heat
- Body secretes fluids via perspiration -> Skin is cooled as perspiration evaporates
- Removal of body waste
- Amniotic fluid, joint lubricants, saliva, bile
- Blood transport
Water
Fluid Balance
Water conducts electricity poorly; to control movement of water, salts separates into ions (electrolytes) and balance is maintained by a balance of cation and anion concentrations
* HOW? Controlled by the electrolyte concentration
“Where ions go, water is sure to follow”
Osmosis:
* Movement of water from a less concentrated to a more concentrated solution
Water
Water balance - Input and output
Water Input
* Drinking
* Water content of foods
* Metabolic synthesis
Water losses
* Urine
* Skin (perspiration)
* Lung
* Faecal
Water
Regulation of Water Balance - physiological responses
- Physiological responses – e.g., thirst
▪ Relatively insensitive: about 2% of the body’s fluid must be lost before activation of
the thirst response
Responses
▪ Conscious feeling of thirst (via hypothalamus)
Water
Regulation of Water balance - Hormones
2) Hormones
If water level is too low, hypothalamus sends signals to the pituitary gland to release hormones:
- Angiotensin is a powerful vasoconstrictor (narrows diameter of blood vessels, increases blood pressure)
- ADH is a water conserving hormone that stimulates the kidney to reabsorb water
- Aldosterone is a steroid hormone (regulates salt and water in the body)
Water
Regulation of Water Balance - Enzymes
3) Enzymes
▪ Renin: low blood pressure releases an enzyme called renin (by kidney)
▪ Renin regulates aldosterone (retains sodium) and angiotensin (increase blood pressure)
Water
Dehydration
- Water losses accentuated in hot climates, with exercise and in fever and illness (e.g. diarrhoea, burns)
- As extracellular fluid is lost, osmolarity increases, and water is drawn from within cells to the extracellular fluid
Water
Dehydration Symptoms
- 1-2% loss: thirst, economy of movement, anorexia (loss of appetite), increased pulse, nausea
- 3-6 % loss: dizziness, headache, absence of saliva, inability to walk
- 7-10% loss: delirium, swollen tongue, inability to swallow, deafness, dim vision, shrivelled skin
Water
Toxicity of Water?
Excess water without sufficient electrolyte intake overwhelms excretion capacity
of kidneys → dilutes extracellular fluids Na+
(hyponatraemia)
↓ Na+ → water moves from extracellular fluids to intracellular fluids → water enters
brain → cerebral oedema
Sodium
Sodium Role
- Sodium is the main cation outside the cells (ECF) and one of the primary electrolytes for maintaining fluid balance
- principle positive ion (cation) in the extracellular fluid
- Aldosterone regulates sodium balance
Sodium
Deficiency of Sodium
- rare
- Symptoms related to blood pressure and cell volume
- Muscle cramps, nausea, vomiting, dizziness, shock, coma
- Athletes: Losing too much sodium and drinking too much water can lead to hyponatraemia
Chloride
Chloride Role
Chloride is the major anion (negative ion) outside the cells and works closely with sodium (Salt = sodium chloride)
* main role in maintaining fluid balance and is part of digestion through hydrochloric acid.
Potassium
Potassium Role
- Potassium is important for maintaining fluid balance too
- primary cation (positive ion) inside the cell
Potassium
Food Sources of Potassium
- found in fruits, vegetables, milk, grains, meats and dried beans
