HOMEOSTASIS Controlling our internal environment: How many factors can you name that the body has to regulate and control? Discuss and write a list.

– Temperature – Water balance – Gas levels- Oxygen and CO2. – PH – Blood sugar level. – Salt levels.

Homeostasis Maintenance Internal Environment Water Balance/Salt or Ion Balance Kidneys Concentrate Urine/Dilute Urine Sweat/Breath Temperature control Optimum enzyme activity Sweat/Shiver Blood Sugar Pancreas

CORE BODY TEMPERATURE Human beings have a core body temperature of about 37°C. Normal range= °C Heat is generated from respiration. Affected by external environment. =f50KsEJ8rgA =f50KsEJ8rgA

INCREASING BODY TEMPERATURE Warm external environment. Exercise. Temperature in cycling velodrome is kept at 28 o C

WHY 37°C ??? Chemical reactions in cells happen quickest at that temperature.

ENZYMES: Tiny proteins in the body responsible for many cell functions. E.g. Respiration.

High temps change enzyme structure so they don’t work Low temps mean reactions happen more slowly

When it is too hot: Sweat is produced. This sits on the surface of the skin and evaporates. This uses up heat energy from the body, cooling us down.

Sweating The skin

When it is too hot: The blood vessel beneath the skin dilate (becomes wider) More blood flows near the surface of the skin. More heat from the blood is radiated out to the environment. This cools us down. This is called VASODILATION.

If the temperature rises, the blood vessel dilates (gets bigger). This means more heat is lost from the surface of the skin

Increasing heat loss

EXTREMES OF TEMPERATURE

TOO HOT!!!! Heat Exhaustion- Core temp reaches 40°C Symptoms: Nausea Feeling faint Heavy sweating Can lead to heat stroke

This experiment is to find out how being wet and a breeze leads to loss of body heat. It also demonstrates how sweating cools down the body. » Fan How Cyclists Keep Their Cool

1.Use four beakers. 2.Wrap them all in the same amount of paper towel. 3.Soak the cotton wool around two of them. 4.Pour equal amounts of warm water into each. (A temperature of about 40 ºC is a model of the body’s temperature.) 5.Put a thermometer in the beakers. Place one dry and one wet beaker on the desk and also one wet and one dry in front of the fan. 6.Record the temperatures over a period of about 8 minutes in the results table below. 7.Draw a graph and plot the sets of points. Draw two curves of best fit. 8.Display your results as a line graph, with all four sets of results on the same axes.

Conclusions 9Write down your conclusions from this experiment. 10In your experiment what part of the body does the paper towel represent? 11What benefit is there from the cyclists experiencing air resistance? 12 What disadvantage is there from the cyclists experiencing air resistance?

HEAT STROKE UNCONTROLLED INCREASE IN BODY TEMP

TASK Produce a Leaflet/ A4 poster warning about the dangers of Heat Stroke and how it differs from Heat Exhaustion. Include how body and why body temperature is controlled. Include tips on prevention and also how to treat someone suffering with heat stroke.

CAUSE

Exposure to hot temperatures leads to Increased sweating which leads to dehydration. This results in decreased sweating and an increase in core body temp.

HEAT STROKE Core temp above 40°C Symptoms: Confusion Rapid, shallow breathing Unconsciousness Organ failure Brain damage death