A.2.1

Electrolytes are minerals in the body that carry an electrical charge when dissolved in fluids like blood, sweat, and urine. They are essential for many physiological functions, including hydration, nerve signaling, muscle contractions, and pH balance.

About 2/3 is Intracellular fluid (ICF) inside cells About 1/3 is Extracellular fluid (ECF) is outside cells 80% is interstitial fluid (fluid between tissues) 20% is blood plasma Higher sodium ion (Na+)

50-70% of body mass is water

Greater fat percentage means lower water percentage as fat does not contain any water So the more muscle you have the more water because there is water in muscle

The large intestine reabsorbs water from undigested food, preventing dehydration. It also absorbs the electrolytes from food Prevents dehydration by reclaiming water. Maintains electrolyte balance for muscle and nerve function. Supports waste elimination by forming solid stool.

Chloride, Magneisuim, sodium, Bicarbonate, Calcium, potassium

Regulates fluid balance, nerve function, and muscle contractions. It comes from salty foods

Maintains heart functions, muscle contraction and nerve signals come from banaas potaos and spinach

Supports bone health muscle contractions and blood clotting comes from dairy or leafy greens

Aids muscle relaxation energy production and nerve function comes from nuts seeds and wholegraims

Helos maintian fluid balance and stomach aid production sewed table salt tomatoes

Regulates PH in the body produced natrually in motaolism

about 2.5 liters

Evaporation from the skin (sweat) Evaporation from respiratory tract (breathing) Excretion from kidneys (urine) Excretion from large intestine (faeces)

When water levels drop, the body is dehydrated (hypohydrated) or has high levels of electrolytes (hypertonic) more ADH is released and the hypothalamus also activates sensation of thirst, which increases the desire to drink fluids. This causes the kidneys to reabsorb more water and produce less urine, restoring the balance When water levels rise, the body is hyperhydrated and has low levels of electrolytes (hypotonic), less ADH is released and the kidneys reabsorb less water.

water through food fluid intake and metabolic water

more water, lower concentration of solutes) - less ADH released so kidneys reabsorb less water, leaving more in the blood and returning body to isotonicity

stable concentration of solutes

(less water, higher concentration of solutes) - more ADH is released so kidneys reabsorb more water and hypothalamus increases thirst sensations causing intake of more water, returning the body to an isotonic state)

(high blood sodium) - where blood sodium levels are above 145mmol/L and often caused by loss of water rather than excess sodium intake

(low blood sodium) - where blood sodium levels are below 135mmol/L and often caused by excess water intake or sodium loss

Urnine anylsis, body mass changes, hydrometer, osmometer

Delayed Response – Thirst typically occurs when body water loss reaches 1–2% of body weight, which can already impair cognitive and physical performance. Exercise & Heat – During intense activity or in hot climates, sweat loss exceeds thirst signals, leading to hypohydration. High Humidity – In humid conditions, reduced sweat evaporation makes fluid loss less noticeable, delaying thirst.

hletes need more fluid as they experience more sweat loss due to evaporation to dissipate heat from muscle contraction during exercise