OCR AS Bio Chapter 11: Health and Disease (P192-196)

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Smoking and the cardiovascular system

Smoking increases the risk of developing CHD (coronary heart disease). Nearly everyone who develops CHD in their early 30s/40s is a smoker. Smoking can cause high blood pressure. A smoker with high blood pressure has 20X greater risk of stroke than a non-smoker without high blood pressure.

Nicotine

This is one of the causes of high b.p. Nicotine in cigarettes is a neurotoxin (chemical that damages the nervous system). It is used as an insecticide. Nicotine is addictive making it hard for smokers to stop.

Nicotine molecules are relatively small so can pass easily out of the blood and into every part of the body (including the brain). Nicotine increases the levels of dopamine (a transmitter substance) in parts of the brain known as 'reward circuits'. Activation of these circuits gives a feeling of pleasure which causes enjoyment when smoking.

Nicotine is also the cause of releasing adrenaline into the blood. Adrenaline increases the rate of heart beat, blood pressure and breathing rate.

Carbon Monoxide

This diffuses from the alveoli into the blood in lung capillaries. Here it combines with haemoglobin, forming a bright red compound called carboxyhaemoglobin. The compound is held together tightly as haemoglobin has a very high affinity for carbon monoxide. When haemoglobin forms this compound less is available to transport oxygen. Therefore, smoking reduces the delivery of oxygen to the tissues, including the heart muscle. There is less energy available to smoker's muscles when they exercise.

Hypertension, CHD and stroke

Nicotine increases blood pressure increasing the risk of developing atherosclerosis and CHD (Chapter 10) But it isn't just the coronary arteries that are affected- atherosclerosis can develop in any of the body's arteries. Smokers again run a higher risk than non-smokers of atherosclerosis developing in blood vessels which lead to the brain.

If a clot develops in one of these blood vessels it will starve the brain of oxygen. Brain cells have a…

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