The immune system is your body's defence network against pathogens — bacteria, viruses, fungi, and parasites. It operates on two levels: innate immunity (fast, non-specific) and adaptive immunity (slower, highly specific).
The innate system responds immediately to anything recognised as foreign. Skin is the first barrier. If pathogens breach it, immune cells like neutrophils and macrophages attack using inflammation — redness, swelling, and heat are signs of this response working.
The adaptive system is slower but devastatingly precise. When the innate system flags a threat, specialised white blood cells called T cells and B cells are activated. B cells produce antibodies — proteins specifically shaped to bind to that particular pathogen and neutralise it. T cells directly destroy infected cells.
Memory cells remain after infection resolves, enabling faster response to the same pathogen years later. This is how vaccines work — they trigger this memory formation without causing the disease itself.
Autoimmune diseases occur when the immune system mistakenly attacks the body's own tissues — conditions like rheumatoid arthritis, lupus, and type 1 diabetes.
by yareddesta81071
· 6 upvotes
Earthquakes occur when stress accumulated along geological fault lines is suddenly released. Tectonic plates — the massive sections of Earth's crust — are constantly moving, typically a few centimetres per year. Where plates meet, they grind against each other. Friction prevents smooth sliding, so stress builds up over decades or centuries until it releases catastrophically.
The point underground where the earthquake originates is the hypocentre (or focus). The point on the surface directly above is the epicentre, which is what news reports refer to. Seismic waves radiate outward in all directions from the hypocentre.
The Richter scale and more modern moment magnitude scale measure energy released. The scale is logarithmic — a magnitude 7 is about 32 times more energy than a magnitude 6. A magnitude 9 releases about 1,000 times more energy than a magnitude 7.
Earthquakes are concentrated along plate boundaries: the Pacific Ring of Fire (Japan, Indonesia, Chile), the Alpine-Himalayan belt, and mid-ocean ridges. But intraplate earthquakes can occur far from boundaries and are often harder to predict.
by lekefashola34415