B2 Keeping Healthy REVISION

How do our bodies resist infection? Harmful microorganisms reproduce quickly inside the body, because it is w______ and they have enough f_____ and w_____ They cause disease symptoms if they DAMAGE CELLS or MAKE POISONS that damage cells.

Microbes: our defence against them Our bodies have four major defence mechanisms against invading microbes: If our skin is cut platelets seal the wound by clotting The breathing organs produce mucus to cover the lining of these organs and trap the microbes The skin acts as a barrier Our blood contains white blood cells

How do our bodies resist infection? Micro-organisms …… pathogens Skin Stomach acid Cilia White blood cells

Fighting disease If microbes enter our body they need to be neutralised or killed. This is done by WHITE BLOOD CELLS: White blood cells do 3 things: 1)They eat the microbe 2)They produce antibodies to neutralise the microbe 3)The produce antitoxins to neutralise the poisons produced by microbes

Producing antibodies Step 1: The white blood cell “sees” the antigen (microbe) Step 2: The cell produces antibodies to “fit” the antigen Step 3: The antibodies fit onto the antigens and cause them to “clump” Step 4: The antigens are “eaten” by the white blood cells You’re going down

Remember Your body makes a different antibody to recognize every type of MO that enters it. Some of the white blood cells that make each antibody stay in your body. When the MO invades your body again your body quickly makes the correct antibody.

Vaccines Vaccine contains dead or inactive parts of the MO White blood cells make antibodies against the MO Antibodies are made quickly if the dangerous MO enters your body at a later date You are now IMMUNE

Should we vaccinate everyone? Vaccines can have side effects But for society as a whole vaccination is the best choice, A high percentage of the population need to be vaccinated to prevent epidemics of infection

Why is it hard to vaccinate against some diseases? The flu virus changes quickly – costly The HIV virus changes quickly in the body. It damages the immune system. So there is no effective vaccine. Can’t stop me!

Antibiotics can destroy invading bacteria or fungi First Prize For becoming resistant to antibiotics By Mutating!

Developing and Testing Drugs A new drug is tested for safety and effectiveness on lab grown human cells and animals The drug is tested on healthy volunteers to test for safety The drug is tested with the illness to test for effectiveness and safety

Making Drug Trials ‘fair’ One group of ill people takes the new drug One group of people takes the existing treatment for the illness. Placebos look like the treatment but have no drug in them. They are not used in human trials. Some trials are double blind – no one knows who takes what. Some trials as blind – doctors know but patients don’t.

The heart pumps blood around the body so it needs a continuous supply of energy I get my energy from respiration. Respiration uses oxygen and glucose. I need blood to supply these. The coronary arteries supply blood to the heart

Arteries, veins and capillaries Arteries carry high pressure blood away from the heart. They have smaller lumen and no valves. Veins carry low pressure blood back to the heart. They have thinner, less elastic walls and have valves to prevent backflow of blood. Capillaries have thin walls (one cell thick) to allow glucose and oxygen to pass through. Also used to connect arteries to veins. “Lumen”

Heart Attack! Fat builds up in the coronary artery walls A blood clot may form on this fat The clot can block the artery The blockage stops oxygen getting to the heart muscle Heart cells die, and the heart is permanently damaged

Risk Factors Smoking Poor diet Excess alcohol Stress Lack of exercise