Coronary Heart Disease (CHD)

Heart diseases are often diet related.

- high levels of salt

- high saturated fat

- stress

- not enough exercise

- smoking

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Atherosclerosis

Build up of fatty deposits in the walls of arteries - atheroma

Atheroma causes the the artery walls to thicken and narrow - reducing blood flow; oxygen and glucose to cells

Layer of cells lining artery become damaged -> triggers and inflammatory response, white blood cells accumulate cholesterol (atheroma)

Calcium salts and fibrous tissues build up causing swelling on the inner wall - plaques - ARTERY LOSES ELASTISITY

Plaque causes artery lumen to narrow -> increases blood pressure

Plaques lead to raised blood pressure, which lead to more plaques - positive feedback

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LDLs and HDLs

LDLs - (Low Density Lipoprotein)

note: lipoproteins are complex substances containing both fatty (triglycerides and cholesterol) and protein componenrs and are made in the liver

note: cholesterol is essential for the formation of cell membranes and some hormones

- involved in the formation of atheroma

- transport cholesterol from the liver to the tissues, including artery walls

These are bad

HDLs - (High Density Lipoprotein)

- remove cholesterol from the tissues and transport it to the liver where it is removed/ excreted 

These are good

When a diet contains excess fats, particularly saturated fats, the quantity of LDLs rises - increasing the risk of Coronary Heart Disease

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Thrombosis

Atheromas restrict blood flow and increase the chance of blood clots.

Thrombus: stationary blood clot

Embolism: moving blood clot

Blood clots prevent the supply of blood to the tissues beyond the clot - the cells are deprived of oxygen and glucose and will die.

note: it is the cells that die and not e.g. the heart

Blood clot in the coronary artery - coronary thrombosis

Bits of the clot may break off and cut off the blood supply in smaller arteries, possibly causing a heart attack (or just damages heart tissue)

Blood clots grow, blocking off the lumen causing a heart attack

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Aneurysm

Damage to artery walls may start to bulge due to increased blood pressure.

This swelling is called an aneurysm.

Artery walls are damaged by: high blood pressure and toxins from cigarette smoke

The swelling can burst, causing internal bleeding, depriving the cells of oxygen and glucose

Aneurysms occur in the coronary arteries (heart) and cerebral arteries (brain) and are the main cause of strokes

Strokes can damage and kill cells; symptoms include paralysis, loss of speech and blurred vision

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Myocardial Infarction (Heart Attack)

An indicator of atheroma is angina

Sympotms of angina: pain in the centre of the chest, difficulty breathing, dizziness

(particularly during exercise) -> area of heart muscle starved of oxygen, heart muscle cells respire anaerobically, lactic acid builds up which causes pain

Most heart attacks are caused by blood clots in the coronary arteries

- Heart muscle deprived of oxygen and the muscle cells die -> heart muscle can no longer contract

Symptoms of a heart attack: crushing chest pain radiating to neck, jaw and arms; breathlessness; weak pulse

Severe damage to heart muscle can result in reduced cardiac output 

cardiac output = stroke volume x heart rate

SV - the volume of blood pumped out in 1 beat (cm^3)

HR - the number of beats per minute

unit of CO - cm^3min^-1

This results in less blood pumped out in a given time

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Risk Factors for CHD

Age and sex - risk increases with age (atheromas develop slowly over time; increasing over time);      men more at risk (females produce more oestrogen)

Genetic factors - CHD tends to run in families; lifestyle does play a part, though

Carbon monoxide - combines with haemoglobin in red blood cells, forming carboxyhaemoglobin ->     reduces oxygen carrying capacity in the blood; raised blood pressure (causing     atheroma); chest pain.

     meaning the heart must work harder to supply the same volume of blood

Nicotine - stimulates the production of adrenaline -> increasing blood pressure and heart rate; makes       the platelets 'sticky' leading to thrombosis

High blood pressure - affected by lifestyle factors; high pressure means the heart must work harder                and is more prone to failure; artery wall damage (aneurysm and bursting);        arteries may thicken and harden, reducing blood flow

Blood cholesterol - HDLs, remove cholesterol from tissues for excretion (helps protect arteries from    heart disease); LDLs, transport cholesterol from liver to tissues leading to heart    disease

Diet - high levels of salt (increases blood pressure); high levels of sat fat (increases the LDL density)

Antioxidants - reduces risk of heart disease

Non-starch polysaccharides - reduce risk because they absorb lipids e.g. fibre/cellulose

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