Unit 3 - Glucagon (H)
The amount of glucose, or sugar, in the blood must be kept within certain levels. This is the first of two GCSE Biology quizzes looking at how the body regulates blood sugar levels with hormones, and it concentrates on how glucagon is used to increase the amount of glucose in the blood.
If you measure the blood glucose level of two people who haven't eaten for several hours, it would normally be between 4 to 6 mmol/l. If the test subjects then swallow a glucose drink, measuring the level again would give a reading of higher than the top value, perhaps around 8 - 10 mmol/l. But if the level is measured again, about 30 minutes later, it would be lower, with exercise, it could even be back down into the normal range. Somehow, the body regulates its blood sugar level. It does this by using two hormones, insulin and glucagon. Glucose is required for the process of respiration so it is important to always have the right concentration in the bloodstream. The regulation of glucose involves the liver and also the pancreas.
When the level of glucose in the blood is high, it stimulates the pancreas to release the hormone insulin. Hormones are chemical messengers and insulin makes the liver remove the glucose and store it as glycogen. This can then be released later by turning it back into glucose, when blood sugar levels are low, for example when you have not eaten for a long time or when you have been doing prolonged exercise.
Glucagon is a hormone which is released from the pancreas in response to low blood glucose levels. When blood glucose levels are low, glucagon causes cells in the liver to convert glycogen into glucose. This enters the blood and restores blood glucose levels back to normal again. If levels of glucose fall too low and stay too low, it is called hypoglycaemia. Apart from leaving you feeling tired, if it continues, it will lead to dizziness, unconsciousness and finally death - if your cells cannot get enough glucose, respiration stops and you die.
The pancreas of some diabetes sufferers cannot produce glucagon and so they are in danger of hypoglycaemia which is why they usually always carry with them some sugary food like a chocolate bar. When they feel the first signs of the hypoglycaemia coming on, they eat, restoring their blood sugar levels. This may not always be possible for severe diabetics so they carry a glucagon emergency kit. This can be used to inject glucagon directly into the bloodstream and within a few minutes, blood sugar levels are raised to a safer level once more.
What is homeostasis? Which organ synthesises glucagon? Try this quiz to see how much you know about how the body regulates the levels of glucose in its blood with glucagon.
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