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Blood Glucose Regulation: Insulin and Glucagon Maintain Balance

Blood glucose levels must be carefully regulated to maintain homeostasis.
Two hormones, insulin and glucagon, work in opposition to keep blood glucose levels within a narrow, healthy range.
These hormones are produced by the pancreas and act on target cells throughout the body.

The Pancreas Detects and Responds to Glucose Changes

The pancreas serves as both a sensor and responder in regulating blood glucose.
Dual Function of the Pancreas:
1. Exocrine Function: Produces digestive enzymes to aid in digestion.
2. Endocrine Function: Contains islets of Langerhans, which house two types of cells:
  1. Alpha Cells: which secrete glucagon to increase blood glucose.
  2. Beta Cells: which secrete insulin to decrease blood glucose.

Negative Feedback Loop Maintains Balance

Blood glucose regulation relies on negative feedback to maintain homeostasis.

High Blood Glucose (after eating):
1. Beta cells detect high glucose and secrete insulin.
2. Insulin causes cells to absorb glucose and the liver to store glucose as glycogen.
3. Blood glucose levels decrease.
4. As glucose returns to normal, insulin secretion stops (negative feedback).
Low Blood Glucose (between meals):
1. Alpha cells detect low glucose and secrete glucagon.
2. Glucagon causes the liver to break down glycogen and produce glucose.
3. Blood glucose levels increase.
4. As glucose returns to normal, glucagon secretion stops (negative feedback).

Tip

Insulin and glucagon work in opposition to maintain blood glucose balance.
Insulin lowers it, glucagon raises it.

What happens to glucose in the liver and muscles when insulin is released?

Blood glucose concentration must stay within a narrow range for homeostasis. When conditions change (like eating or exercising), the body uses control systems to keep internal conditions stable enough for cells to function properly.

If blood glucose moves outside its healthy range, there are important consequences:

Too low: brain cells have too little fuel for respiration.
Too high: can damage tissues over time and disrupt water balance.

DefinitionhomeostasisMaintenance of a stable internal environment (within limits) despite external changes.

Analogy

Think of blood glucose like the temperature in a house: it can rise after “input” (a meal) or fall when fuel is used up, but control systems keep it near a set range.

Common Mistake

Students often think “homeostasis means constant.” It actually means “kept within limits,” not perfectly constant.

Written by official IB examiners

Blood Glucose Regulation: Insulin and Glucagon Maintain Balance

Blood glucose levels must be carefully regulated to maintain homeostasis.
Two hormones, insulin and glucagon, work in opposition to keep blood glucose levels within a narrow, healthy range.
These hormones are produced by the pancreas and act on target cells throughout the body.

The Pancreas Detects and Responds to Glucose Changes

The pancreas serves as both a sensor and responder in regulating blood glucose.
Dual Function of the Pancreas:
1. Exocrine Function: Produces digestive enzymes to aid in digestion.
2. Endocrine Function: Contains islets of Langerhans, which house two types of cells:
  1. Alpha Cells: which secrete glucagon to increase blood glucose.
  2. Beta Cells: which secrete insulin to decrease blood glucose.

Negative Feedback Loop Maintains Balance

Blood glucose regulation relies on negative feedback to maintain homeostasis.

High Blood Glucose (after eating):
1. Beta cells detect high glucose and secrete insulin.
2. Insulin causes cells to absorb glucose and the liver to store glucose as glycogen.
3. Blood glucose levels decrease.
4. As glucose returns to normal, insulin secretion stops (negative feedback).
Low Blood Glucose (between meals):
1. Alpha cells detect low glucose and secrete glucagon.
2. Glucagon causes the liver to break down glycogen and produce glucose.
3. Blood glucose levels increase.
4. As glucose returns to normal, glucagon secretion stops (negative feedback).

Tip

Insulin and glucagon work in opposition to maintain blood glucose balance.
Insulin lowers it, glucagon raises it.

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What happens to glucose in the liver and muscles when insulin is released?

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If blood glucose moves outside its healthy range, there are important consequences:

Too low: brain cells have too little fuel for respiration.
Too high: can damage tissues over time and disrupt water balance.

DefinitionhomeostasisMaintenance of a stable internal environment (within limits) despite external changes.

Analogy

Think of blood glucose like the temperature in a house: it can rise after “input” (a meal) or fall when fuel is used up, but control systems keep it near a set range.

Common Mistake

Students often think “homeostasis means constant.” It actually means “kept within limits,” not perfectly constant.

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

D3.3.3 Regulation of blood glucose as an example of the role of hormones in homeostasis Notes

Blood Glucose Regulation: Insulin and Glucagon Maintain Balance

The Pancreas Detects and Responds to Glucose Changes

Negative Feedback Loop Maintains Balance

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A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Blood Glucose Regulation: Insulin and Glucagon Maintain Balance

The Pancreas Detects and Responds to Glucose Changes

Negative Feedback Loop Maintains Balance

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