B2 - Keeping healthy

Microorganisms cause disease symptoms if they damage cells or make poisons that damage cells.

white blood cells make antibodies. some of the white blood cells that make each antibody stays in your blood so if invaded another time, can quickly produce antibodies to kill the microorganism.

Flu virus changes quickly. new vaccine needed each year.
HIV virus that causes AIDS mutates quickly inside the body. virus damages immune system. no effective vaccine.

antibiotics kill fungi and bacteria. must only take antibiotics when necessary because some bacteria and fungi can become resistant to antibiotics. Must finish all the tablets even if you feel better. mutation in bacteria and fungi genes can make varieties that are less affected by antibiotics. some of the new varities can survive the antibiotics.

• New drug is tested for safety and effectiveness on lab-grown human cells or animals.
• Healthy volunteers to test for safety
• people with illness to test for effectiveness and safety

in most human trials on ill people, one group of patients takes the new drug. Another group of patients are controls. The controls take either the existing treatment for the illness, or a placebo.

A Placebo looks like the new treatment but has no drugs in it. not often used because people who take them miss out on benefits of both new and existing treatments.

Human trials are blind or double-blind.

Double-blind trials - neither patient nor doctors know who is in  which group.
Blind trials trials - doctors know who is in which group but patients do not.

Your heart pumps blood around the body, so heart muscle cells need a continuous supply of energy. This energy come from respiration. Respiriation is a chemical reaction in cells. The reactions uses glucose and oxygen. Energy is released. Blood brings glucose and oxygen to the heart so that the heart needs its own blood supply. Coronary arteries supply blood to the heart.

Most arteries carry blood away from your heart. most veins carry blood towards your heart.

Artery: Thick, elastic muscular wall. Thin space for blood to flow through.
Vein: Thin outer wall. Wider space for blood to flow through.

Coronary arteries carry oxygenated blood to the heart. Fat can build up on the atery walls. Blood clot may form on this fat, blocking ateries. Blockage stops oxygen getting to the heart muscle. Heart cells die and the heart is permanently damaged. this is a heart attack. caused by poor diet, smoking, excess alcohol, stress. regular exercise reduces the risk of heart disease.