10. Diseases and Immunity (Cambridge IGCSE Biology 0610 for exams in 2023, 2024 and 2025)

Summary

This video from IGCSE Study Buddy covers Chapter 10 on diseases and immunity. It explains how pathogens cause diseases, their transmission methods, and the body's defense mechanisms like skin, mucus, stomach acid, and white blood cells. It also delves into active immunity through infection or vaccination, passive immunity from mothers to infants, and the importance of vaccination in controlling disease spread. The video concludes with a discussion on cholera, its transmission, and treatment.

Takeaways

• 🦠 A pathogen is an organism that causes disease and can be transmitted directly through contact or indirectly through various means.
• 🤧 Direct contact transmission includes blood, body fluids, and skin-to-skin contact, such as with chickenpox or HIV.
• 🌀 Indirect contact transmission occurs through contaminated surfaces, food, animals, or air, like through eating contaminated food or mosquito bites.
• 🛡️ The body defends against pathogens with physical barriers like skin and mucus, chemical barriers like stomach acid, and immune cells like white blood cells.
• 🔬 White blood cells, specifically phagocytes and lymphocytes, play crucial roles in the immune response through phagocytosis and antibody production.
• 🧼 Preventing disease involves maintaining a clean water supply, hygienic food preparation, good personal hygiene, proper waste disposal, and sewage treatment.
• 💉 Active immunity is achieved through antibody production in the body following infection or vaccination, providing long-term protection against specific pathogens.
• 🛡️ Antigens on pathogens have unique shapes that antibodies, produced by lymphocytes, can specifically target for destruction or marking for phagocytic destruction.
• 🧬 Memory cells, produced during an immune response, provide long-term immunity by quickly producing antibodies if the same pathogen is encountered again.
• 💊 Vaccination introduces weakened pathogens or their antigens to stimulate an immune response, creating memory cells for future protection without causing illness.
• 🌐 Herd immunity is achieved when a significant proportion of a population is vaccinated, disrupting the chain of infection and preventing disease spread.
• 🍼 Passive immunity is a short-term defense where antibodies are acquired from another individual, such as from mother to child through the placenta or breast milk.
• 🤒 Cholera is a disease caused by a bacterium in contaminated water, leading to severe diarrhea and dehydration, which can be treated with oral rehydration therapy.

Q & A

What is a pathogen?

A pathogen is a disease-causing organism that can be transmitted from one host to another.

How can a transmissible disease be spread?

A transmissible disease can be spread through direct contact, including through blood and other body fluids, or indirectly through contaminated surfaces, food, animals, and air.

What are some examples of direct and indirect transmission of pathogens?

Direct transmission examples include chickenpox, which can spread by touching, and HIV, which requires sexual contact. Indirect transmission examples include eating contaminated food, being bitten by a mosquito carrying a pathogen, or inhaling droplets from an infected person's coughs or sneezes.

How does the body defend itself against pathogens?

The body defends itself through various means such as the skin acting as a physical barrier, nose hairs and mucus filtering pathogens from the air, stomach acid killing ingested pathogens, and white blood cells fighting infections through phagocytosis and antibody production.

What are the two main types of white blood cells involved in the immune response?

The two main types of white blood cells involved in the immune response are phagocytes, which engulf and digest pathogens, and lymphocytes, which produce antibodies.

How can diseases be prevented by simple measures?

Diseases can be prevented by ensuring a clean water supply, hygienic food preparation, good personal hygiene, proper waste disposal, and sewage treatment.

What is active immunity and how is it gained?

Active immunity is a defense against a pathogen by antibody production in the body. It is gained after an infection by a pathogen or through vaccination.

What are antigens and how do they relate to antibodies?

Antigens are uniquely shaped markers on the surface of pathogens' membranes. Antibodies are proteins produced by lymphocytes that have a complementary shape to the antigens, allowing them to bind to and neutralize the pathogens.

What is the role of memory cells in immunity?

Memory cells are produced by lymphocytes that have made antibodies for a particular pathogen. They remain in the blood and can quickly produce the original antibodies if the same pathogen is encountered again, providing long-term immunity.

How does vaccination protect the body against diseases?

Vaccination introduces weakened pathogens or their antigens into the body to stimulate an immune response without causing illness. This leads to the production of antibodies and memory cells, which provide long-term immunity against the disease.

What is herd immunity and how does vaccination contribute to it?

Herd immunity occurs when the majority of a population is vaccinated against a pathogen, breaking the chain of infection and preventing the disease from spreading effectively.

What is passive immunity and how is it acquired?

Passive immunity is a short-term defense against a pathogen by antibodies acquired from another individual, such as from a mother to her unborn baby through the placenta or in breast milk.

How is cholera transmitted and what are its symptoms?

Cholera is transmitted through contaminated water and causes symptoms like diarrhea, which is the loss of watery feces from the anus due to the cholera bacteria producing a toxin that affects the small intestine.

How can cholera-induced diarrhea be treated?

Diarrhea caused by cholera can be effectively treated by Oral Rehydration Therapy, which involves drinking a solution with a small amount of salt and sugar to replace lost fluids and electrolytes.