A.2.1

Question 1

electrolytes

Answer 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.

Question 2

What makes up the water in the body

Answer 2

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+)

Question 2

how much water is in the body

Answer 2

50-70% of body mass is water

Question 3

What does it mean for your water if your fatter or more muscular

Answer 3

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

Question 4

What does the large intestine do and whys it important

Answer 4

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.

Question 5

what are the main elctrolytes

Answer 5

Chloride, Magneisuim, sodium, Bicarbonate, Calcium, potassium

Question 6

Function of sodium

Answer 6

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

Question 7

Function of potassium

Answer 7

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

Question 8

Function of Calcium

Answer 8

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

Question 9

Function of magnesium

Answer 9

Aids muscle relaxation energy production and nerve function

comes from nuts seeds and wholegraims

Question 10

Functon of Chloride

Answer 10

Helos maintian fluid balance and stomach aid production

sewed table salt tomatoes

Question 11

Function of bicarbonate

Answer 11

Regulates PH in the body

produced natrually in motaolism

Question 12

How much water do we loose a day

Answer 12

about 2.5 liters

Question 13

how does water loss occur

Answer 13

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

Question 14

What is the negative feedback loop in water regulation

Answer 14

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.

Question 15

How do we get back in water

Answer 15

water through food fluid intake and metabolic water

Question 16

Hypotonicity

Answer 16

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

Question 17

Isotonicity

Answer 17

stable concentration of solutes

Question 18

Hypertonicity

Answer 18

(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)

Question 19

Hypernatremia

Answer 19

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

Question 20

Hyponatremia

Answer 20

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

Question 21

Ways to measure hydrations levels

Answer 21

Urnine anylsis, body mass changes, hydrometer, osmometer

Question 22

Why is thirst not a perfect indicator of dehydration?

Answer 22

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.

Question 23

Why do athletes need more fluid

Answer 23

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

Question 24

If teh enviroment is hot and dry

Answer 24

Sweat evaporates quickly, making fluid loss less noticeable but still significant. High risk of dehydration due to insufficient water intake. Electrolyte imbalance may lead to muscle cramps, dizziness, and fatigue.

Question 25

if the enviroment is hot and humid hydration..

Answer 25

Increased sweat production leads to high electrolyte loss, especially sodium and chloride. Risk of dehydration and hyponatremia (low sodium levels) if fluids are replaced without electrolytes. Adaptation: The body becomes more efficient at retaining sodium with repeated heat exposure (heat acclimatization).

Question 26

IF teh evnimroent is cold

Answer 26

Reduced thirst response increases the risk of dehydration despite lower sweat rates. 🔹 Increased urine output (cold-induced diuresis) leads to electrolyte loss, especially sodium and potassium. 🔹 Shivering increases energy demand, requiring balanced electrolytes for muscle contraction.

Question 26

If the enviroment is at a high altitude

Answer 26

Increased breathing rate leads to higher bicarbonate loss (affecting acid-base balance). 🔹 Diuresis (higher urine output) results in sodium and potassium loss. 🔹 Adaptation: Over time, the kidneys regulate electrolyte balance to adjust to lo

Question 27

if the enviroment is windy..

Answer 27

bod temp decreases creates enchanced cooling creating a fluid loss risk.

Question 27

hyponatremia

Answer 27

low sodium Sweating loses water and salt Water replaces only water, not salt Sports drinks with electrolytes replace both

Question 28

Signs of hyponatremia

Answer 28

bloating, headache vomiting and nausea.

Question 29

Hyponatremia often occurs in endurance sports and depends on

Answer 29

Duration of the event (e.g low in marathon running but high in ultra marathon running The sport discipline (e.g rare in cycling, frequent in running and triathlon and very frequent in swimming Swimming > running > cycling Biological sex (increased risk of death in biological females) Ambient temperatures (heat increases the risk) Country of competition (USA very common, Asia not)

Question 29

Hypernatremia

Answer 29

When there is a deficit of body water compared to sodium A result of dehydration or excessive sodium in the diet Defined by concentration >145 mmol-1

Question 30

Symptoms of hypertremia

Answer 30

Symptoms are similar to those of hyponatremia which can make it hard to distinguish. Thirst, weakness

Question 31

Cardiac drift

Answer 31

characterized by the gradual increase in heart rate and decrease in stroke volume over time, despite no increase in intensity

Question 32

how does sweating affect blood and stroke volume/cardiac output thing

Answer 32

In prolonged exercise, sweating reduces plasma volume in the blood This sees less venous return to the heart and reduces stroke volume (stroke volume is the amount of blood ejected by the heart per beat) To maintain cardiac output, the heart increases the frequency it is beating (heart rate) to compensate for the decreased stroke volume