Hello Future Biologists! Welcome to Health and Diseases
Ever wondered why you catch a cold, or why some people need to be careful about what they eat? This chapter is all about understanding our health, the diseases that can affect us, and the amazing ways our bodies fight back. It's super important because knowing this stuff helps us make smarter choices to stay healthy and protect our community. Let's get started!
Section 1: So, What Does 'Healthy' Actually Mean?
Being healthy isn't just about not being sick. The World Health Organization (WHO) defines health as a state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity. It’s a three-part package deal!
• Physical well-being: Your body is working properly, you have energy, and you're free from pain.
• Mental well-being: You feel good about yourself, can cope with stress, and handle life's ups and downs.
• Social well-being: You have good relationships with others and feel like part of a community.
A disease is the opposite – it's a condition that impairs the normal functioning of the body and is usually shown by specific signs and symptoms.
Key Takeaway
Health is a balance of physical, mental, and social wellness. A disease is any condition that disrupts this balance.
Section 2: The Two Main Types of Diseases
We can sort most diseases into two big groups: infectious and non-infectious. It's really important to know the difference!
Infectious Diseases
• These are caused by tiny invading organisms called pathogens (like bacteria or viruses).
• They can be passed or 'transmitted' from one person to another.
• Examples: Influenza (the flu), Cholera, Tuberculosis.
Non-infectious Diseases
• These are NOT caused by pathogens and cannot be spread from person to person.
• They are often caused by a mix of genetics, lifestyle choices (like diet and exercise), and environmental factors.
• Examples: Diabetes, Coronary Heart Disease, Cancer.
Key Takeaway
Think of it like this: You can 'catch' an infectious disease, but you can't 'catch' a non-infectious one. The key difference is the cause: pathogens vs. lifestyle/genetics.
Section 3: Infectious Diseases - The Invaders
Let's take a closer look at the diseases caused by those pesky pathogens.
What Causes Them?
Pathogens are microorganisms that cause disease. The main types are bacteria, viruses, fungi, and protists. For your exams, you'll need to know about the diseases they cause, not necessarily the details of each pathogen type.
How Do They Spread? (Ways of Transmission)
Pathogens are sneaky and have many ways to get from one person to another. Knowing these helps us stop them!
• By Water: Drinking contaminated water. Example: Cholera.
• By Air / Droplets: When someone coughs or sneezes, they release tiny droplets full of pathogens. Examples: Influenza, Tuberculosis.
• By Food: Eating contaminated food.
• By Body Fluids: Through contact with infected blood or other fluids. Example: Hepatitis B.
• By Vectors: An animal (usually an insect) carries the pathogen from person to person without getting sick itself. Example: Mosquitoes spreading Dengue Fever.
• By Direct Contact: Touching an infected person or a surface they've touched.
How Do We Fight Back? - Treatment
When we get a bacterial infection, doctors often prescribe antibiotics.
• Action of antibiotics: These are powerful drugs that kill bacteria or stop them from reproducing. They often work by damaging the bacterial cell wall, which our human cells don't have. This is why they don't harm our own cells!
• Indiscriminate use of antibiotics: This is a HUGE problem. If we use antibiotics too often, or don't finish the full course, some bacteria might survive. These survivors can become 'resistant' to the antibiotic. This leads to the creation of "superbugs" that are very difficult to treat.
Quick Review: Common Mistakes
Never use antibiotics for a viral infection like the flu! Antibiotics ONLY work on bacteria. Using them for a virus is useless and contributes to antibiotic resistance. It's like using a key for the wrong lock.
There are also other drugs like sulpha drugs (another type of antibacterial) and antiviral drugs for treating specific diseases.
Key Takeaway
Infectious diseases are spread in various ways, from the air we breathe to the water we drink. We can treat bacterial infections with antibiotics, but we must use them wisely to prevent the rise of resistant bacteria.
Section 4: Non-Infectious Diseases - When Things Go Wrong Inside
These diseases aren't contagious. They are often chronic (long-lasting) and are closely linked to our lifestyle and genes.
Cardiovascular Diseases
These are diseases of the heart and blood vessels. A common one is coronary heart disease. This happens when the arteries supplying blood to the heart muscle get blocked, often by fatty deposits. This is strongly linked to lifestyles with high-fat diets, lack of exercise, and smoking.
Cancer
Cancer is a disease where the body's cells grow and divide uncontrollably, forming lumps called tumours. These cells can invade surrounding tissues. While there are many causes, lifestyle factors like smoking, poor diet, and sun exposure can increase the risk.
Diabetes Mellitus
This is a condition where the body cannot control its blood glucose level properly. Don't worry if this sounds tricky, here's a simple breakdown:
• Insulin-dependent diabetes (Type 1): The body's immune system attacks the pancreas, so it cannot produce insulin. Insulin is the hormone that tells cells to take up glucose from the blood. Without it, blood glucose levels get dangerously high.
• Non-insulin-dependent diabetes (Type 2): The pancreas makes insulin, but the body's cells don't respond to it properly. This is often linked to being overweight and inactive.
Control of insulin-dependent diabetes: People with Type 1 diabetes must regularly monitor their blood glucose levels and take injections of insulin to help their cells absorb glucose, especially after meals.
Did you know?
Before the discovery of insulin as a treatment in the 1920s, getting Type 1 diabetes was a death sentence. The discovery was a massive breakthrough in medicine!
Key Takeaway
Many non-infectious diseases are "lifestyle diseases." This means we can significantly reduce our risk of getting them by making healthy choices like eating a balanced diet, exercising regularly, and not smoking.
Section 5: Our Body's Amazing Defence System
Our body is like a castle, constantly defending against invading pathogens. It has two main levels of defence.
The First Line of Defence: Non-Specific Defences
This is our castle wall. It tries to stop EVERYTHING from getting in, it's not picky!
• Skin: A tough physical barrier.
• Mucus and Cilia: Mucus in our airways traps pathogens, and tiny hairs called cilia sweep the mucus away from our lungs.
• Other Secretions: Tears and saliva contain enzymes that kill bacteria. Stomach acid kills pathogens in our food.
• Blood Clotting: Seals cuts and wounds to prevent pathogens from entering the bloodstream.
• Phagocytes: If a pathogen gets past the barriers, these 'eater' white blood cells find and engulf them. Think of them as the castle guards roaming the halls.
• Inflammatory Response: When you get a cut, the area gets red, swollen, and warm. This is because more blood is flowing to the area, bringing more phagocytes to fight the invaders.
The Special Forces: Specific Defences (The Immune Response)
If pathogens get past the first line, the body launches a highly specific, targeted attack. This is the job of our immune system.
Key Players:
• Antigen: A molecule on the surface of a pathogen that the immune system recognises as 'foreign'. It's like the enemy's uniform.
• Antibody: A protein made by our body that is the perfect shape to lock onto a specific antigen. It's like a guided missile that only targets one type of enemy uniform.
• Lymphocytes: The super-smart white blood cells in charge of this response. There are two main types:
• B cells: When activated, they turn into antibody-producing factories.
• T cells: Some help to activate the B cells, while others directly kill infected body cells.
The Battle Plan: Primary vs. Secondary Response
• Primary Response: The first time you encounter a pathogen. It's slow. It takes time for your lymphocytes to figure out the right antibody to make. While your body is doing this, you get sick. But importantly, your body creates 'memory cells' that remember the antigen.
• Secondary Response: If the same pathogen invades again, the memory cells recognise it instantly. They launch a much faster and stronger response, producing huge amounts of the correct antibody. The pathogens are wiped out before you even feel sick! This is why you usually only get diseases like chickenpox once.
Key Takeaway
Our body has general (non-specific) defences to block all germs and a highly advanced (specific) immune system that learns to recognise and destroy particular pathogens, giving us long-term protection.
Section 6: Prevention is Better Than Cure
We can help our bodies defend against diseases in several ways.
Vaccination: Training Your Immune System
This is one of the greatest inventions in medicine! Here's the principle:
Principle of Vaccination: A vaccine contains a safe version of a pathogen – it might be a dead pathogen, a weakened one, or just the antigens from it. This is injected into the body. It can't make you sick, but it's enough for your immune system to launch a primary response and, crucially, produce memory cells. Now, if you ever encounter the real, dangerous pathogen, your body will immediately launch a powerful secondary response and you won't get ill. Vaccination gives you immunity without having to suffer the disease first.
Advantages: Protects individuals and the community (herd immunity).
Risks: Very rare side effects like allergic reactions can occur.
Active vs. Passive Immunity
This is a really important concept to get right!
• Active Immunity: YOUR body actively produces its own antibodies and memory cells. It's slow to develop but is long-lasting.
How you get it:
- Natural: By getting infected with the disease.
- Artificial: Through vaccination.
• Passive Immunity: You are GIVEN antibodies that were made by another person or animal. It gives immediate protection, but it's temporary because your body didn't make the antibodies or memory cells, so they eventually break down.
How you get it:
- Natural: A baby gets antibodies from its mother through the placenta and breast milk.
- Artificial: An injection of antibodies (e.g., for a snake bite or tetanus).
Memory Aid: Active vs. Passive
Active = Your body Achieves it. It's a long-term achievement.
Passive = The antibodies are Passed to you. It's a short-term present.
Healthy Lifestyle and Community Health
Finally, the simplest things are often the most effective!
• Healthy Lifestyle: A balanced diet, regular exercise, and enough sleep keep your whole body, including your immune system, strong. This helps prevent both infectious and non-infectious diseases.
• Community Health: We all have a personal responsibility to keep our community healthy. This includes good personal hygiene (washing hands!), proper waste disposal, and getting vaccinated to protect those who can't be.
Key Takeaway
We can prevent diseases through powerful tools like vaccination (which builds active immunity) and by making smart daily choices for ourselves and our community.