Human Coordination » Adrenaline and Insulin

What you'll learn this session

Study time: 30 minutes

The role of hormones in human coordination
How adrenaline functions as a fight-or-flight hormone
The structure and function of insulin
How insulin regulates blood glucose levels
The causes and effects of diabetes
How negative feedback systems work in hormone regulation

Hormones in Human Coordination

Our bodies need to respond to changes both outside and inside us. While the nervous system provides rapid responses through electrical signals, hormones offer a slower but longer-lasting form of coordination through chemical messengers.

Key Definitions:

Hormones: Chemical messengers produced by endocrine glands that travel in the bloodstream to target organs.
Endocrine glands: Specialised organs that release hormones directly into the bloodstream.
Target organs: Specific organs that have receptors for particular hormones and respond to them.

📖 Hormone vs Nervous System

Nervous System: Fast responses, short-lasting effects, specific pathways

Hormonal System: Slower responses, longer-lasting effects, widespread distribution via bloodstream

🌐 The Endocrine System

The endocrine system consists of glands that secrete hormones directly into the bloodstream. Major endocrine glands include the pituitary gland, pancreas, adrenal glands, thyroid and ovaries/testes.

Adrenaline: The Fight-or-Flight Hormone

Adrenaline (also called epinephrine) is a hormone released by the adrenal glands in response to stress, fear, excitement, or danger. It prepares the body for immediate action - either to fight or flee from a threat.

How Adrenaline Works

When you face a stressful situation (like seeing a scary dog or before an exam), your adrenal glands release adrenaline into your bloodstream. This hormone quickly travels throughout your body, triggering various responses:

💓 Heart & Lungs

• Increases heart rate
• Raises blood pressure
• Makes breathing faster
• Widens airways

🍜 Digestion & Energy

• Slows digestion
• Releases glucose from liver
• Increases blood glucose
• Redirects blood to muscles

💪 Muscles & Senses

• Dilates pupils
• Heightens alertness
• Increases muscle tension
• Reduces feeling of pain

Real-Life Example: The Adrenaline Rush

Have you ever felt suddenly alert when startled? Maybe your heart raced before a presentation? That's adrenaline at work! Athletes often experience an "adrenaline rush" during competitions, giving them a temporary boost in strength and reaction time. This is why people can sometimes perform extraordinary feats in emergency situations, like a parent lifting a heavy object to save their child.

Insulin: The Blood Sugar Regulator

Insulin is a hormone produced by the pancreas that plays a crucial role in regulating blood glucose levels. It helps cells absorb glucose from the bloodstream, which they need for energy.

How Insulin Regulates Blood Glucose

After we eat carbohydrates, they are broken down into glucose which enters the bloodstream. The pancreas detects this rise in blood glucose and releases insulin in response:

👇 When Blood Glucose Rises

1. Carbohydrates from food are digested into glucose
2. Blood glucose levels increase
3. Beta cells in the pancreas detect high glucose
4. Pancreas releases insulin into bloodstream
5. Insulin helps cells absorb glucose
6. Liver converts excess glucose to glycogen for storage
7. Blood glucose levels decrease

👆 When Blood Glucose Falls

1. Blood glucose levels drop (e.g., between meals)
2. Alpha cells in pancreas detect low glucose
3. Pancreas releases glucagon (not insulin)
4. Glucagon signals liver to convert glycogen back to glucose
5. Liver releases glucose into bloodstream
6. Blood glucose levels increase

Negative Feedback Systems

Both adrenaline and insulin work as part of negative feedback systems. A negative feedback system helps maintain balance (homeostasis) by reversing any change from the normal state.

🔃 How Negative Feedback Works

1. A change occurs in the body (stimulus)
2. Receptors detect the change
3. Information is sent to a control centre
4. The control centre triggers a response
5. The response counteracts the original change
6. The system returns to normal

🗺 Example: Blood Glucose Regulation

When blood glucose rises → insulin is released → glucose is removed from blood → blood glucose falls → insulin secretion stops

When blood glucose falls → glucagon is released → glucose is added to blood → blood glucose rises → glucagon secretion stops

Diabetes: When Insulin Regulation Fails

Diabetes is a condition where the body cannot regulate blood glucose levels properly, either because it doesn't produce enough insulin or because cells don't respond to insulin correctly.

💉 Type 1 Diabetes

Cause: The immune system attacks and destroys insulin-producing cells in the pancreas.

Features:
• Usually develops in childhood or adolescence
• Body produces little or no insulin
• Requires insulin injections
• Not linked to lifestyle factors

🍽 Type 2 Diabetes

Cause: Cells become resistant to insulin and the pancreas can't make enough insulin to overcome this resistance.

Features:
• Usually develops in adults (but increasing in younger people)
• Often linked to obesity and inactivity
• Can often be managed with diet, exercise and medication
• May eventually require insulin

Case Study: Managing Diabetes

Emma was diagnosed with Type 1 diabetes at age 12. She needs to monitor her blood glucose levels regularly and inject insulin before meals. If her blood glucose gets too low (hypoglycaemia), she needs to eat something sugary quickly. If it gets too high (hyperglycaemia), she needs extra insulin. By carefully managing her diet, exercise and insulin doses, Emma can live a normal, healthy life despite having diabetes. Modern technology like continuous glucose monitors and insulin pumps has made management easier for many people with diabetes.

Comparing Adrenaline and Insulin

⚡ Adrenaline

Source: Adrenal glands

Trigger: Stress, danger, excitement

Main function: Prepare body for action

Effects: Increases heart rate, blood pressure and blood glucose; diverts blood to muscles

Duration: Short-term (minutes)

Evolutionary purpose: Survival in dangerous situations

🍰 Insulin

Source: Pancreas (beta cells)

Trigger: High blood glucose

Main function: Lower blood glucose levels

Effects: Promotes glucose uptake by cells, glycogen storage in liver

Duration: Medium-term (hours)

Evolutionary purpose: Energy storage and utilisation

Key Points to Remember

Hormones are chemical messengers that travel in the bloodstream to affect target organs
Adrenaline is released in response to stress and prepares the body for "fight or flight"
Insulin is released when blood glucose levels rise and helps cells absorb glucose
Both hormones are part of negative feedback systems that maintain homeostasis
Diabetes occurs when the body cannot produce enough insulin or respond to it properly
Type 1 diabetes is caused by lack of insulin production, while Type 2 is usually caused by insulin resistance

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