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

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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


  • 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

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Ruth graduated from Sheffield University with a degree in Biology and went on to teach Science in London whilst also completing an MA in innovation in Education. With 10 years of teaching experience across the 3 key science disciplines, Ruth decided to set up a tutoring business to support students in her local area. Ruth has worked with several exam boards and loves to use her experience to produce educational materials which make the mark schemes accessible to all students.