Regulating Water Balance

What are electrolytes and their function in the body?

Electrolytes (e.g., sodium, potassium) dissolve in blood and sweat, regulating fluid balance and muscle contraction.

What happens if blood solute levels are too high?

Osmosis draws water out of cells, leading to dehydration.

What is overhydration and its impact on blood osmolarity?

Overhydration without electrolyte replenishment decreases blood osmolarity, potentially leading to hyponatremia.

Define hypernatremia.

Hypernatremia is a condition characterized by high sodium concentration (> 145 mmol), leading to cell dehydration.

What are early symptoms of hyponatremia?

Early symptoms include bloating, nausea, vomiting, headache, and brain swelling.

Define hyponatremia.

Hyponatremia is a condition characterised by a low sodium concentration (<135 mmol)

What factors increase the risks of hyponatremia in athletes?

Risks increase with the duration of performance, type of sport, biological sex, and environmental conditions.

Why do athletes need more fluids during exercise?

Exercise and hot environments increase sweat loss, disrupting water balance, requiring electrolyte replenishment.

What percentage of body mass should athletes not exceed in fluid loss due to dehydration?

Athletes should not lose more than 2% of body mass due to dehydration.

What is cardiovascular drift?

Cardiovascular drift refers to an increase in heart rate and a decrease in stroke volume over time during prolonged exercise.

When is cardiovascular drift more noticeable?

In hot environments

Measuring Water and Electrolyte Balance

What is monitored before and after exercise?

Body Mass

How can urine color indicate hydration status?

Dark urine indicates dehydration, while pale urine indicates normal hydration.

Osmosis Measurements

Berkeley-Hartley Method

Osmometer

Measures solute concentration in plasma or urine using freezing point depression or vapor pressure

Advantages of osmometer

Highly accurate and reliable

Disadvantages of osmometer

Requires specialised equipment and trained personnel

Hydrometer

Measures urine solute concentration by comparing density to water

Advantages of hydrometers

Simple, portable

Disadvantages of Hydrometer

Affected by recent fluid intake and diet

What is the role of the kidneys in water regulation?

The kidneys control water and electrolyte retention/loss, filtering them from the blood into the glomerulus.

How does the Loop of Henle function in water absorption?

The Loop of Henle absorbs water out of the tubule, concentrating the fluid and reducing its volume.

What is also actively transported out of the loop of henle?

Sodium chloride reducing the volume even more

What is the function of ADH in the Collecting Duct?

ADH increases permeability in the Collecting Duct, allowing for greater water reabsorption before urine excretion.