Responses to Extremes (OCR GCSE Biology A (Gateway))

How Humans Cope with Extreme Conditions

Higher Tier Only

• 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

Temperature Challenges

High Temperatures

• 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

Low temperatures

• 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

Osmotic Challenges

Dehydration

• 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

Over hydration

• 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

Excess salt intake

• 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