UNIT 4: Homeostasis
Chapter 10: The Endocrine System
pg. 466
10.3: Regulating Blood Sugar
pg. 483 - 487
The regulation of blood sugar occurs automatically, and is controlled by the
endocrine system. The body used glucose for fuel therefore it must regulate
blood sugar levels to maintain homeostasis.
Individuals that have problems maintaining their blood glucose levels and
monitoring systems have a condition known as Diabetes Mellitus. Diabetics
have blood glucose levels that fluctuate abnormally, changing their
metabolism and leading to other serious health problems. Diabetics must
monitor their blood sugar levels all the time and take insulin to maintain
appropriate levels.
Hormones That Control Blood Sugar
islets of Langerhans – are endocrine cell clusters inside the pancreas that
produce insulin and glucagons.
The pancreas is the organ responsible for secreting the two main hormones
to control blood sugar levels. Specialized cells called the islets of
Langerhans produce protein hormones insulin and glucagon. These two
hormones work together regulate the ability of most tissues to metabolize
fuel substances.
After eating blood sugar level increase, this triggers (beta cells) the release
of insulin, which lowers the blood sugar levels, by instructing target cells to
take up the excess sugar. Insulin also inhibits the breakdown of glycogen
into glucose.
Glucagon is secreted by alpha cells in the islets of Langerhans, work
oppositely to insulin. Glucagon is responsible for increasing blood sugar
levels by stimulating the breakdown of glycogen into glucose in the liver.
Glucagon also stimulates the breakdown of fats into fatty acids and proteins
into amino acids, alternative energy sources.
Figure 2: the opposing actions of insulin
and glucagon work together through
negative feedback mechanisms to maintain
the blood glucose level.
Figure 3: Typical levels of blood glucose and insulin over
a 24 h period.
Diabetes
Diabetes mellitus – is a disease in which the blood glucose level is too high
because of the insufficient production or activity of the hormone insulin.
Type I diabetes – is a type of diabetes caused by an inability to produce
insulin.
Type II diabetes – is a type of diabetes caused by low insulin or an inability
to use insulin.
Diabetes Mellitus, commonly known as diabetes, is characterized by high
blood glucose levels caused by problems with insulin production. 6%
percent of the world’s population is affected by diabetes.
There are three classic symptoms of diabetes are; frequent urination,
increased thirst, and increased appetite, all lead to a high glucose
concentration in the blood. This also impacts the kidneys, with a high
glucose concentration cause more water to move by osmosis into the
nephron to dilute the glucose, increasing urine production. This in turn
causes the need to replenish water lost, therefore a person becomes thirsty.
Since glucose is leaving in the urine, a person needs to eat more to replenish
lost glucose fro cellular function, this leads o an increase in appetite.
Type I: beta cells in the islet of Langerhans (pancreas) do not produce
insulin. This type of diabetes can occur in infancy or early childhood,
therefore it is called juvenile diabetes. This type of diabetes needs to be
closely monitored and regular administration of insulin is required for
treatment.
Type II: is caused by the reduction of insulin production, and usually occurs
during adulthood and is associated with obesity. 90% of diabetics have type
II and is associated to genetic links to other family members over
generations. Type II diabetes can be treated by controlling diet and exercise
to restore normal glucose levels.
The third type of diabetes is called gestational diabetes and onset during
pregnancy. 2 to 10% of pregnant women may have temporary diabetes, but
this is a risk to the mother and baby.