Conditions inside our body

The conditions inside our body must be very carefully controlled as operates within a narrow range of temperature and pH.

carry messages around the body, but they work in a very different way to the structures in the nervous system.

	Hormones	Nervous system
Type of message	Chemical	Electrical
Carried by	Blood	Neurones
Speed of transmission	Slow	Fast

Type of message
Hormones	Chemical
Nervous system	Electrical

Carried by
Hormones	Blood
Nervous system	Neurones

Speed of transmission
Hormones	Slow
Nervous system	Fast

A hormone is a chemical messenger produced in the endocrine glands and carried in the blood to a target organ. A hormone called is involved in the regulation of sugar (glucose) in the blood.

Regulating blood glucose

is needed by cells for . It is important that the concentration of glucose in the blood is maintained at a constant level. Insulin is a hormone produced by the that regulates glucose levels in the blood.

Action of insulin

	Low glucose	High glucose
Effect on pancreas	Insulin not secreted into the blood	Insulin secreted into the blood
Effect on liver	Does not convert glucose into insoluble glycogen	Converts glucose into insoluble glycogen for storage
Effect on blood glucose level	Increases	Decreases

Effect on pancreas
Low glucose	Insulin not secreted into the blood
High glucose	Insulin secreted into the blood

Effect on liver
Low glucose	Does not convert glucose into insoluble glycogen
High glucose	Converts glucose into insoluble glycogen for storage

Effect on blood glucose level
Low glucose	Increases
High glucose	Decreases

The diagram shows how this works.

Too much glucose. Pancreas produces insulin, body cells absorb glucose, blood glucose reduced. Normal levels, insulin not produced by pancreas, less glucose absorbed, blood glucose remains same.

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Homeostasis – WJECConditions inside our body