POINT!

When blood glucose is decreased, negative feedback inhibits insulin (synthesis, secretion, and concentration in blood).

(Synthesis, secretion, and concentration in blood of) insulin decreases blood glucose. Before fast, insulin has certain levels of synthesis, secretion, concentration in blood, and blood glucose-decreasing effect.

① Subject had fasted. Blood glucose is decreased due to the fasting. Insulin (synthesis, secretion, and concentration in blood) decreases blood glucose. These are in the same direction (red).

② Since these are in the same direction (red), negative feedback inhibits (blue) insulin (synthesis, secretion, and concentration in blood). Because of this, the blood glucose-decreasing effect of glucagon weakens, and the decrease in blood glucose (blue downward unfilled arrow) disappears (decreased blood glucose increases to the baseline).

Like, when room temperature is decreased (winter), cooler (function) is decreased, this is also red→blue negative feedback.

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