Biology - Regulatory Mechanisms in Animals
Regulatory Mechanisms in Animals
This resource explores regulatory mechanisms in animals including: the
regulation of glucose levels, thermoregulation, osmoregulatory mechanisms
and countercurrent heat exchange systems.
The normal concentration of glucose in human blood is about
90mg/100cm3. It is important that the level of glucose is maintained
between fairly narrow limits. Levels normally increase after meals, but
continuously high levels, as in the disorder diabetes, result in
hyperglycaemia, which leads to dehydration and diabetic coma. Excess
glucose is normally converted to glycogen  (animal starch) or fats, and
stored. A low level of glucose results in hypoglycemia, leading to
convulsions and coma.
two hormones  control or regulate the level of blood glucose
* insulin (produced by cells of the pancreas) acts to lower blood glucose
by increasing the uptake of glucose by cells; too little insulin, as in
diabetes, results in hyperglycaemia; too much insulin results in
* glucagon  (produced by a cells of pancreas) acts to raise the level
of glucose by causing glycagon in the liver to be broken down to glucose,
which is released
Regulation operates in response to the negative feedback mechanism.
As blood glucose levels drop, or in situations of fright or flight
emergency, nerve stimulation of the adrenal gland results in the rapid
production of adrenalin, which acts on liver cells to cause the breakdown
of glycogen to glucose. More glucose is made available for cellular
respiration in preparation for release of energy if action is required.
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