Transcript Homeostasis - ScienceGeek.net

Homeostasis
Maintaining
an
Internal Balance
Homeostasis
• The property of a system, either open
or closed, that regulates its internal
environment so as to maintain a stable,
constant condition.
• Multiple dynamic equilibrium adjustment
and regulation mechanisms make
homeostasis possible.
Source: Wikipedia
Blood Glucose – An Example
• Glucose is the simple sugar known as
“blood sugar”
• Glucose is required for brain function –
the brain cannot use any other energy
source
• A healthy body maintains a blood sugar
level of between 80 mg/dL and 110
mg/dL (slightly higher right after
meals)
The Role of Hormones
When blood glucose levels are low, the hormone
glucagon stimulates the conversion of glycogen
in the liver to glucose
Glucagon is a peptide hormone made of 29
amino acids. It is produced in the alpha cells of
the (α-cells) of the islets of Langerhans, which
are located in the pancreas.
The Role of Hormones
When blood glucose levels are high, the
hormone insulin stimulates the conversion of
glucose to stored glycogen in the liver.
Insulin is a peptide hormone made of 51 amino
acids. It is produced in the beta cells of the
(β-cells) of the islets of Langerhans, which are
located in the pancreas.
Type I Diabetes
• Autoimmune disease destroys the beta
cells of the pancreas
• Diabetic is dependent on exogenous
insulin
• There is currently no cure, though
there many approaches under research
• In North America, 5 – 10% of diabetics
are Type I
Type II Diabetes
• A metabolic disorder due to insulin
resistance (the cells are insensitive to
the insulin that is present)
• Onset of disease can be postponed by
proper nutrition and exercise
• 90 – 95% of North American diabetics
are Type II.
• 20% of the population over age 60 are
Type II
Blood Calcium: Example #2
• Ca2+ ion is essential to organisms. It is
functions include:
– A component of bone
– Neurotransmission and muscle contraction
– Fertilization
– As a cofactor in processes such as blood
clotting
Calcium Homeostasis
When blood calcium levels are low, the hormone
parathyroid hormone, produced in the
parathyroid glands, promotes
 absorption of calcium in the intestine
 conservation of calcium by the kidneys
 release of calcium from bone tissue
Calcium Homeostasis
When blood calcium levels are high, the
hormone calcitonin, produced in the thyroid
gland, promotes
 elimination of calcium by the kidneys
 storage of calcium in bone tissue