Environment: Control of Blood Glucose

Blood glucose level in organisms is controlled by two types of hormones, insulin and glucagon. This system of regulation helps to maintain a stable internal environment, which is essential for survival of organisms.

Basics of Blood Glucose Regulation

Glucose is a type of sugar that provides energy for various cellular functions. It is derived from carbohydrate-rich foods such as bread, pasta, and sugar.
Blood glucose refers to the concentration of glucose in the bloodstream.
The body strives to maintain blood glucose levels within a narrow optimal range - usually between 4 and 7 mmol/L.

Role of the Liver

The liver plays a crucial role in blood glucose regulation by storing excess glucose in the form of glycogen after a meal when blood glucose levels are high.
When blood glucose levels are low, the liver can convert stored glycogen back into glucose and release it into the bloodstream.

Role of Insulin

Insulin is a hormone produced by β-cells of the islets of Langerhans in the pancreas.
When blood glucose levels are high, for example after eating, insulin is released into the bloodstream.
Insulin promotes the uptake of glucose by cells, stimulating them to convert glucose into energy or store it as glycogen, thereby reducing the blood glucose levels.

Role of Glucagon

Glucagon is a hormone produced by α-cells of the islets of Langerhans in the pancreas.
When blood glucose levels are low, for example, during fasting, glucagon is released into the bloodstream.
Glucagon stimulates the liver to convert stored glycogen into glucose and release it into the bloodstream, thereby increasing the blood glucose levels.

Role of Adrenaline

Adrenaline is often known as the ‘fight or flight’ hormone and is released during times of stress.
Adrenaline also raises blood glucose levels by stimulating the breakdown of glycogen into glucose.

Diabetes - Disruption in Blood Glucose Regulation

Diabetes is a disease characterised by a disruption in the regulation of blood glucose levels.
In Type 1 diabetes, the body does not produce insulin, leading to high blood glucose levels that can be controlled through regular insulin injections.
In Type 2 diabetes, the body’s cells become resistant to insulin, leading to high blood glucose levels that can be controlled through diet, exercise, and medication.

Understand that maintaining blood glucose levels in the body involves a complex interplay between different organs and hormones. Recognise the potential health implications when these control systems malfunction.