Staying in Balance – Revision Pack (B1)
Homeostasis:
By definition, homeostasis is keeping a constant internal environment. It involves
balancing bodily outputs and inputs.
Automatic control systems in the body help to maintain temperature, water and
carbon dioxide levels. This ensures that cells can work at their optimum (best) level.
Negative feedback controls are also used in homeostasis. The negative feedback
systems act to cancel out a change such as a decreasing temperature.
Temperature control:
The temperature of the body should be maintained at 37oC – this is because many
of the body’s enzymes work best at this temperature; it is their optimum.
When the body gets too hot:
-
Heat stroke can happen – the skin becomes cold and slimy and your pulse
rate is fast, yet weak
Dehydration can happen – this is where too much water is lost
Both of these can lead to death if not properly treated.
Sweating is used as a defence mechanism to avoid overheating. Sweating increases
the transfer of heat to the surrounding environment. The evaporation of sweat
requires body heat to transfer the (liquid) sweat into water vapour (gas).
When we get too cold, in very low temperatures, hypothermia can set in. This causes
violent shivering and a slowed pulse – it can be fatal if not treated quickly.
The hypothalamus is part of the brain that monitors the
temperature of the blood in your body.
The actual reaction to temperature extremes (too cold /
too hot) is controlled by the hormonal and nervous
systems, which trigger vasodilation or vasoconstriction.
Vasoconstriction is the constriction
(narrowing) of small blood vessels in the
skin. It causes less blood flow and less
heat transfer.
Vasodilation is the dilation (widening) of
small blood vessels in the skin. This causes
more blood to flow near the surface of
the skin, resulting in more heat transfer.
Staying in Balance – Revision Pack (B1)
Controlling blood sugar levels:
Hormones are chemicals that travel to target organs to regulate the functions of
organs and cells. Insulin is an example of a hormone; it is produced in the pancreas
and lowers blood glucose levels when they get too high. When your body lacks
insulin diabetes is caused.
Hormone reactions are lower than nervous reactions as hormones travel in the
blood.
There are two types of diabetes:
Type of diabetes
1
Cause
Method of Control
Person’s pancreas does
Insulin injections at
not produce any insulin
mealtimes.
2
Occurs later in life and
Controlled diet
linked with being
overweight. Person’s body
produces too little insulin
or their body doesn’t react
to the insulin
Insulin converts excess glucose into glycogen, which is stored in the liver. This helps to
regulate the blood sugar level.
The insulin dosage for people with Type 1 diabetes will vary according to the
person’s diet and amount of activity.
For example, when we do strenuous activity we need more glucose in our blood for
energy, so a lower insulin dose would be needed for someone with Type 1 diabetes.
Staying in Balance – Revision Pack (B1)
Past Papers:
PPQ(1):
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PPQ(2):
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PPQ(4):
PPQ(5):
Staying in Balance – Revision Pack (B1)
PPQ(6):
Staying in Balance – Revision Pack (B1)
Mark Schemes:
PPQ(1):
PPQ(2):
PPQ(3):
PPQ(4):
PPQ(5):
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Staying in Balance – Revision Pack (B1)
PPQ(6):