Hormonal control
Hormonal systems
Hormones are chemical messengers. Hormones are released into the bloodstream by groups of cells called A gland that produces and releases a hormone directly into blood.. Hormones are transported in the blood plasma to target body tissues where they bind to cells to produce a response.
A specific hormone can only affect cells if the cells have a receptor for it. The diagram below shows two cells targeted by two different hormones. Hormone one cannot affect the cell on the right because the cell does not have a receptor for it.
Blood glucose regulation
The concentration of glucose in the blood must be kept at a set point.
If the blood glucose concentration rises too high then the water concentration of the blood will fall and water will diffuse out of cells by osmosis. This may interfere with cell reactions.
If the blood glucose concentration falls too much, then body cells will not receive as much glucose and so will not be able to release as much energy in respiration.
The concentration of glucose in the blood is regulated by the action of the hormones A hormone that regulates the level of sugar in the blood and can be produced by genetically modified bacteria. and A hormone produced by the pancreas that promotes the breakdown of glycogen into glucose in the liver.. The target cells of these hormones are found in the liver.
The liver acts as the body's glucose 'reservoir'. Liver cells can take in glucose molecules from the blood using insulin and store them in the form of Animals store glucose as glycogen in their liver and muscle tissues.. Glycogen can be broken down again using glucagon and the glucose released into the blood when it is needed.
The diagram shows how the concentration of glucose in the blood is regulated.