Responses to Extremes (OCR Gateway GCSE Biology: Combined Science)

Revision Note

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Last updated

19 May 2022

The mechanisms of homeostasis allow the human body to survive in a range of environmental conditions whilst maintaining optimum internal conditions for enzyme action and healthy cell function
If the body is unable to adjust to extremes of environmental conditions, it may result in illness or even death
Extreme conditions could include
- Temperature challenges: Very high or very low temperatures
- Osmotic challenges: Excessively high salt intake, water intake or dehydration

When body temperature exceeds 37.5 °C. it is called a fever
At a temperature of 38.3 °C or more, hyperthermia develops
If not treated carefully, the results could be severe and even fatal
Hyperthermia may occur in response to
- Drugs e.g. stimulants such as cocaine, ecstasy or methamphetamine
- Heat stroke from dehydration and prolonged exposure to heat e.g. sun
Symptoms include:
- Tiredness, dizziness and headaches
- Low blood pressure
- Muscle cramps
- Heavy sweating and intense thirst
- Urine produced will be low in volume and darkly coloured
- Nausea
- Cramps in arms, legs and stomach
Treatments include:
- Moving to a cool place
- Lie down and raise legs
- Drink fluids e.g. rehydration drinks
- Apply cool flannels or spray with cool water

When body temperature drops below 35 °C, hypothermia develops
If not treated, hypothermia can worsen to become exhaustion hypothermia and eventually death
Hypothermia may happen in response to
- Sudden or prolonged exposure to cold (e.g. falling into cold water)
- Getting cold whilst wearing wet clothes
- Exposure to lesser extremes could have the same outcome in babies or elderly people who are more at risk
Symptoms include:
- Shivering
- Slow breathing
- Slurred speech
- Tiredness
- Pale skin
- Low energy
Treatment includes:
- Warming the patient up slowly
- Removing wet clothes and wrapping in dry blankets or towels
- Ensure they are sheltered, ideally indoors
- Warm sugary drinks (non-alcoholic)
- In serious cases, treatment in hospital may be required to provide oxygen or intravenous warm fluids

If the body loses more water than it takes in, dehydration occurs
- This can happen in hot conditions when sweating increases and fluid intake isn't sufficient
- Vomiting or diarrhoea will increase the chances of dehydration
- Diabetes is also a risk factor
Dehydration can impact the kidneys as they try to reabsorb as much water as possible
Symptoms include:
- Feeling thirsty
- A dry mouth
- Tiredness
- Dizziness
- Small volumes of concentrated dark coloured urine
Treatment includes
- Consuming more water
- Intake of salts to replace those lost through sweating

Consuming too much water is also dangerous as it can lead to water intoxication
The results can be fatal as the excess water leads to swelling in the body, particularly the brain
Symptoms include
- Headaches
- Personality or behavioural changes
- Irritation
- Disorientation and confusion
- Drowsiness
- Nausea
In serious cases
- Seizure
- Brain damage
- Coma or death
Treatment includes:
- Reduce fluid intake
- Use diuretics to increase urine production

High salt levels (or hypernatremia) may occur due to excessive intake of salt or due to increased water loss (e.g. through sweating, vomiting or diarrhoea)
Excessive salt intake can impact the kidneys
Diabetics, babies and the elderly are at a higher risk than others
Symptoms include:
- Thirst
- Confusion
- Muscle twitching
- Fatigue
In serious cases,
- Seizures
- Bleeding in the brain
- Kidney damage or kidney failure
Treatment includes:
- Careful control of fluid and sodium intake
- In serious cases, an intravenous supply of balanced fluids may be required

the (exam) results speak for themselves:

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