Homeostasis: Blood Glucose

See how negative feedback keeps conditions in the body stable, using temperature and blood glucose as examples.

About 3 min read
  • Define homeostasis
  • Explain negative feedback
  • Describe control of body temperature
  • Describe control of blood glucose
Before you start

You know that enzymes need suitable conditions, and that hormones and nerves carry signals around the body.

Keeping conditions stable

Cells work best when their surroundings stay within narrow limits. Homeostasis maintains conditions such as temperature, water balance and blood glucose. Receptors detect a change, a control centre processes the information, and effectors respond to return the condition towards normal.

Definition: homeostasis

The maintenance of a stable internal environment.

Definition: negative feedback

A control process in which a change triggers a response that reverses the change.

Body temperature

The hypothalamus monitors blood temperature. When you are too hot, skin arterioles widen and sweat evaporates to transfer heat away. When you are too cold, arterioles narrow, muscles shiver and metabolism increases.

Blood glucose

After a meal, blood glucose rises. The pancreas secretes insulin, and liver and muscle cells take in glucose and store it as glycogen. If glucose falls, the pancreas secretes glucagon and the liver breaks glycogen down into glucose.

Trace a feedback loop

Describe what happens after blood glucose rises.

Pancreatic cells detect the rise and secrete insulin.

Insulin makes target cells absorb glucose and convert it to glycogen.

Blood glucose falls back towards normal, so insulin release decreases.

Answer: The response reverses the original rise.

Spell the hormones carefully

Glucagon is a hormone. Glycogen is the storage carbohydrate. Glucose is the blood sugar.

Exam focus
Say it like this“Arterioles near the skin dilate, so more blood flows near the surface.”
Not like this“Blood vessels move closer to the skin.” — Vessels widen. They do not move.
Common mistakeMixing up glucagon, glycogen and glucose in written answers.

Practice

Which organ secretes insulin?
The pancreas.
Which part of the brain monitors blood temperature?
The hypothalamus.
State one response to being too hot.
Sweating or vasodilation of skin arterioles.
Going further
Explain why type 1 diabetes causes blood glucose to rise after a meal.
The pancreas produces little or no insulin, so cells do not take in enough glucose and less is stored as glycogen.

Quick check

Homeostasis quick check

What is negative feedback?

It brings a condition back towards its normal range after it moves away.

Which hormone lowers blood glucose?

It causes cells to take in sugar and the liver to store it.

What happens to skin arterioles when you are cold?

Narrowing reduces blood flow near the surface, so less heat is lost.
Key takeaways
  • Homeostasis keeps internal conditions stable.
  • Negative feedback reverses a change.
  • The hypothalamus controls body temperature.
  • Insulin and glucagon control blood glucose.
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