| Coronary heart disease (CHD) | - Type of cardiovascular disease
- Occurs when coronary arteries have lots of atheromas in them
- Restricting blood flow to heart
- Can lead to myocardial infarction |
| What is the cardiac cycle | - Heart undergoes a sequence of events that is repeated 70 times each min when at rest
- 2 phases of the beating of heart: contraction (systole) + relaxation (diastole) |
| Contraction of the atria (atrial systole) | - Ventricles relax
- Atria contract
- Decreasing volume of chambers
- Increasing pressure inside chambers
- This pushes blood into ventricles
- Slight increase in ventricular pressure + chamber vol
- AV valves are open
- Semi lunar valves are shut |
| Contraction of the ventricles (ventricular systole) | - Ventricles contract, decreasing their volume, increasing their pressure
- Atria relax
- Blood moves from high to low pressure into
the arteries
- Pressure higher in ventricles than atria, forcing AV valves shut to prevent backflow
- Pressure is also higher in ventricles than aorta + pulmonary artery
- Forces open SL valves + blood forced out into these arteries |
| Relaxation of the heart (diastole) | - Ventricles + atria relax
- Higher pressure in pulmonary artery + aorta closes the SL valves to prevent backflow into ventricles
- Blood returns to heart
- Atria fill again due to higher pressure in vena cava + pulmonary vein
- Increases pressure of atria
- Ventricles continue to relax, pressure falls below pressure of atria
- AV valves open
- Blood flows passively into ventricles from atria
- The atria contract, whole process starts again |
| The opening + closing of the valves | - Valves only open 1 way
- Whether they are open or closed depends on the relative pressure of the heart chambers
- Higher pressure behind valve, forced open
- Higher pressure in front of valve, forced shut
- Meaning blood flows only 1 direction in heart |
| Different types of valves | - Atrioventricular valves (AV)
- Semi-lunar valves (SL)
- Pocket valves |
| Atrioventricular valves (AV) | - Links ventricles + atria (left or right depending)
- Prevents backflow of blood from the ventricles into the atrium |
| Semi-lunar valves (SL) | - Link ventricles + pulmonary artery + aorta (depends)
- Prevents backflow of blood from the aorta or pulmonary artery into the ventricles |
| Pocket valves | - In veins
- Ensures that when veins are squeezed
- Blood flows back towards heart, rather than away |
| Pressure + volume changes of the heart | - Mammals have closed circulatory system
- Allows pressure within vessels to be maintained + regulated |
| Cardiac output (CO) | - Volume of blood pumped by one ventricle of the heart in 1 min
- Measured in dm3 min-1 |
| What cardiac output depends on | - The heart rate (rate at which heart beats)
- The stroke volume (volume of blood pumped out at each beat) |
| Cardiac output calculation | - CO = stroke volume × heart rate |
| Heart rate calculation | 60/1 cardiac cycle
B.P.M |
| Atheroma | - WBC, lipids, connective tissue build up + harden
- Forming fibrous plaque
- Increases risk of aneurysms + thrombosis |
| Cardiovascular disease and the atheroma formation | - Wall of artery has many layers
- Endothelium usually smooth + unbroken
- If damage occurs to endothelium WBC, lipids build up + harden
- Forming fatty streaks
- Atheroma forms
- Plaque partially blocks artery lumen
- Restricts blood flow
- Increasing blood pressure |
| Aneurysms | - Balloon-like swelling in artery
- Atheroma plaques damage + weaken arteries
- Narrows arteries
- Increasing blood pressure
- Blood travels through weakened artery at high pressure, pushes inner layers through outer elastic layer
- Forming swelling
- May burst, causing haemorrhage (bleeding) |
| Thrombosis | - Formation of blood clot
- Atheroma plaque can rupture (burst through) endothelium of artery
- Damages artery wall, leaves rough surface
- Platelets + fibrin (protein) accumulate at site of damage
- Or become dislodged + block blood vessels
- Debris from rupture can cause blood clots elsewhere |
| Myocardial infarction (heart attack) | - Artery becomes completely blocked, e.g. blood clot
- Area of heart muscle totally cut off from blood supply
- Receives no oxygen
- Causes damage + death of heart muscle
- Shortness of breath, chest pain
- Heart failure if large areas of heart are affected |
| Risk factors of cardiovascular disease | - High blood cholesterol and poor diet
- Cigarette smoking
- High blood pressure |
| High blood cholesterol and poor diet | - Cholesterol 1 of main constituents of fatty deposits that form atheromas
- Increasing blood pressure + clots
- Block flow of blood to coronary arteries, cause heart attack
- A diet high in saturated fat + salt increases BCL |
| Cigarette smoking | - Has nicotine + carbon monoxide
- Nicotine increases blood pressure
- Carbon monoxide binds with haemoglobin, takes up the oxygen carrying capacity in the blood
- Less oxygen available for cells
- Can lead to heart attack, if muscle gets less O2
- Smoking decreases amount of antitoxins
- So cell damage in coronary arteries
- Can lead to atheroma formation |
| High blood pressure | - Increases risk of damage to artery walls
- So increased risk of atheroma formation
- Increasing blood pressure + blood clots
- Blocks blood flow to heart muscle, leading to heart attack
- Being overweight, not exercising, excessive alcohol consumption |
| Coordination of heartbeat | - Myogenic – begins in the muscle
- SAN – Initiates the electrical activity - Pace
maker
- AVN – delays the signal – ‘a gate’
- Bundle of His – conducting fibres (muscle)
- Purkinje Fibres – conducting fibres (muscle)
- Wave of excitation |
