Example 1
Blood glucose rises after a meal. Which hormone response opposes the change?
Insulin release increases. Target tissues take up and store more glucose, bringing blood glucose back towards its regulated range.
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Year 9
Hormones and blood-glucose control
Compare hormone and nerve signals and apply the insulin–glucagon feedback pattern.
Method and worked examples
Endocrine glands release hormones into the bloodstream. A hormone reaches many places, but only target cells with suitable receptors respond. Hormonal responses are often slower and longer-lasting than nerve impulses. Nervous and endocrine systems cooperate rather than functioning as isolated alternatives. Blood transport allows a gland to influence distant target organs without a direct nerve connection to each target cell.
When blood glucose rises, pancreatic cells release insulin, promoting glucose uptake and storage, which lowers blood glucose towards its usual range. When glucose falls, other pancreatic cells release glucagon, promoting glucose release from liver stores. These are negative feedback responses: the response opposes the original change. Insulin does not add glucose to blood, and glucagon does not simply turn into glucose.
Example 1
Example 2
A signal travels in blood but only some cells respond. Explain why.
The signal can be a hormone. Target cells have suitable receptors; cells without those receptors do not produce that hormone-specific response.
Watch out: Negative feedback counteracts a deviation. A rise triggers responses tending to lower the regulated variable.