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Table of Contents
Blood sugar level
Body temperature
The body's water content
Controlling water content of the body
Ion (salts) content of the body
Controlling body temperature
Control mechanisms
Controlling temperature
Thermoregulation - Higher tier
Too hot
Too cold
Hormones produced by glands and their target organs
Blood glucose regulation
How glucose is regulated
Glucagon ­ Higher tier
Type 1 diabetes
Type 2 diabetes
The direction of plant growth
Responses of different parts of the plant
Plant hormone experiments…read more

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Receptors and effectors
Different receptors
Reflex actions
PAGE 4…read more

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Conditions in the body are controlled, to provide a constant internal environment. This
is called homeostasis. The conditions that must be controlled include body
temperature, water content, carbon dioxide level, and blood sugar level. Diabetes is a
condition where the body cannot effectively regulate the levels of blood sugar.
It is important that the body's internal environment is controlled. For example, the
amount of carbon dioxide in the bloodstream must be carefully controlled.
Maintaining a constant internal environment is called homeostasis.…read more

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Controlling water content of the body
This is controlled to protect cells by avoiding too much water entering or leaving them.
Water content is controlled by water loss from:
the lungs when we exhale
the skin by sweating
the body, in urine produced by the kidneys
Ion (salts) content of the body
This is controlled to protect cells by avoiding too much water entering or leaving them.…read more

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Blood vessels can shrink down again - vasoconstriction. This reduces heat loss
through the skin once the body's temperature has returned to normal.
Muscles can also receive messages from the brain when you are cold. They respond by
shivering, which warms you up.
Controlling temperature
Too cold Too hot
A Hair muscles pull hairs on end. D Hair muscles relax. Hairs lie flat so heat can escape.
B Erect hairs trap air. E Sweat secreted by sweat glands. Cools skin by evaporation.…read more

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Too cold
muscles contract rapidly and we shiver when we're cold. These contractions need
energy from respiration, and some of this is released as heat.
Vasoconstriction occurs - blood vessels leading to the skin capillaries become
narrower (constrict) letting less blood flow through the skin and conserving heat in the
The hairs on the skin also help to control body temperature. They lie flat when we are
warm, and rise when we are cold.…read more

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Use the animation to make sure you understand how this works.
Glucagon ­ Higher tier
The pancreas releases another hormone, glucagon, when the blood sugar levels fall.
This causes the cells in the liver to turn glycogen back into glucose which can then be
released into the blood. The blood sugar levels will then rise.
Blood sugar level meter and insulin shot pen
Diabetes is a disorder in which the blood glucose
levels remain too high. It can be treated by
injecting insulin.…read more

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Rising levels of obesity and type 2 diabetes are linked.
As obesity is a risk factor for type 2 diabetes doctors are keen to monitor the situation.
Someone is considered obese is they have a body mass index (BMI) of more than 30.
BMI is calculated by:
Plant hormones
A 'tropism' is a growth in response to a stimulus. Plants grow towards sources of water
and light, which they need to survive and grow.…read more


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