FOOD20003 Lecture Notes - Lecture 20: Magnesium, Vasopressin, Extracellular Fluid
28 Jun 2018
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WATER AND MAJOR MINERALS
1. Describe the fluid compartments of the body.
• Intracellular fluid = water inside the cell
• Extracellular fluid = water outside of the cell
o Interstitial/intercellular fluid – fluid between cells that is high in Na/Cl à provides cells
with required ingredients
o Intravascular fluid – fluid within blood vessels (i.e. plasma)
• Role of water:
o Carries nutrients/wastes, metabolic reactions, solvent, lubricant, maintain body volume
• Intake: diet & as by-product of metabolism
• Loss: urine (kidneys), sweat, breathing, faeces
• Dehydration can result in severe health effects – dizziness, muscle spasms, exhaustion
2. Outline the main features of water regulation including the role of the kidneys, hypothalamus,
pituitary gland, antidiuretic hormone (ADH), renin, angiotensin and aldosterone.
Kidneys – Blood volume and pressure
• Blood volume correlates with blood pressure which are controlled by:
o Antidiuretic hormone (ADH)
§ Released from pituitary in response to concentrated blood, low blood volume or low
blood pressure
§ Stimulates kidneys to reabsorb more water & decrease excretion in urine
o Renin-angiotensin system
§ Measures blood pressure
§ Low BP: release enzyme renin, which activates angiotensin
§ Angiotensin = constricts blood vessels à increase pressure
• Stimulates release of aldosterone
o Cause kidneys to reabsorb sodium (and hence water via osmosis)
o Water follows the movement of ions
3. Discuss the main electrolyte levels in extracellular and intracellular fluid.
• Electrolytes = salt ions/charged minerals
• There’s an electrical balance of +ve/-ve inside/outside the cell
• BUT overall charge density/ion type inside the cell is diff to
outside the cell
o Measured in miliquivalents (mEq)
• Function: control movement of water
4. Describe osmotic pressure and the movement of fluid.
