biology - synoptic

biology - synoptic

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  • Created on: 26-05-10 11:43
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The factors which influence the concentration of glucose in the blood
Our body's primary source of energy takes the form of glucose. This type of sugar comes
from digesting carbohydrates into a chemical that we can easily convert to energy. The
normal blood glucose level is 90mg 100cm3. As we do not eat continuously and our diet
varies, the intake of glucose fluctuates. In the fasting state (90mg 100cm3) glycogen is
constantly being broken down in the liver cells into a simpler chemical called glucose which is
then transported into the blood stream at such a rate as to maintain the blood glucose level
at around 90mg 100cm3. This breakdown of liver glycogen is controlled by nerves of the
autonomic nervous system which consists of two divisions, the sympathetic and the
parasympathetic. Three main hormones, insulin, glucagon and adrenaline operate to maintain
a constant blood glucose level.
Many factors affect the concentration of glucose in the blood, such as, diabetes. People
with Diabetes either: don't make insulin in the islet cells of their pancreas because their
immune system has accidentally attacked them. These people have type 1 diabetes and
have to inject insulin OR
have become resistant to their own insulin or don't make enough. Their liver might even make
more glucose. These people have type 2 diabetes which sometimes can be controlled with
diet & exercise, or with tablets that increase sensitivity to insulin and decrease the amount
of glucose made by the liver. In people with diabetes, sugar (glucose) accumulates in the
blood to very high levels. The excess glucose can attach to proteins in the blood vessels
and alter their normal structure and function. When people are treated it may lead to
hypoglycaemia (low blood sugar). When blood glucose begins to fall, glucagon (another
hormone made by the pancreas) signals the liver to break down glycogen and release
glucose into the bloodstream. Blood glucose will then rise toward a normal level. In some
people with diabetes, this glucagon response to hypoglycemia does not function well and
other hormones such as adrenaline may raise the blood glucose level. Adrenaline is produced
by the adrenal glands. Its action on the liver is to ease the breakdown of liver glycogen with
subsequent rise of the blood sugar.
Alcohol is another factor that influences the concentration of blood glucose. Alcohol
interferes with all three sources of glucose and the hormones needed to maintain healthy
blood glucose levels. Heavy drinkers reduce their glycogen stores within a few hours when
their diet does not provide enough amounts of carbohydrates. Over time, excessive alcohol
consumption can decrease insulin's effectiveness, resulting in high blood sugar levels.
Alcohol can also negatively impact blood sugar levels each time it's consumed. Small
amount of alcohol consumption increases insulin secretion, causing low blood sugar
(hypoglycemia), and can also damage the hormonal response that would normally correct the
low blood sugar.
Exercise is great for lowering blood glucose because glucose is a rapid form of energy, and
when we exercise our body needs energy quickly. There are certain conditions under which
blood glucose can actually increase from exercise. Blood glucose being too high always
means that there is not enough insulin available to bring the level down. When exercise

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More glucose is needed
and because such large amount of glucose is not available from the bloodstream and via the
insulin transport mechanism, it is taken directly from the glycogen stored in the muscle.
Insulin is not needed for this. The hormone glucagon is required for glycogen to be turned
into glucose, and it is secreted into the bloodstream when adrenaline levels go up.…read more


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