In this IBDP Biology Blog, we will learn the important components of:
- Systole and Diastole aka Cardiac Cycle
- Coronary Artery Disease
The Cardiac Cycle
Systole: A period of contraction
Diastole: A period of relaxation
- Diastole is normally longer than Systole
- Blood moves through the heart due to differences in pressure
Atria Systole
- Atria walls
contract
- Blood
pressure is higher in atria than ventricles
- Blood passes from atria to ventricles through the atrio-ventricular valves which are open
- The semilunar valves are closed
Ventricular Systole
- Ventricle walls
contract and blood pressure rises within them
- Forces the atrio-ventricular
valves to close - to prevent blood backflow into atria
- Semilunar valves open
- Blood
pumped out into arteries
- Artia are
relaxed (collect blood from veins)
Diastole
- The ventricles
relax
- Pressure in the ventricles falls below that of the artia
- Semilunar valves close - prevent
backflow [produces dub]
- When ventricle pressure falls below that of atria the atrio-ventricular valves open
- Blood enters from veins into atria and flows to ventricles
- The next cardiac cycle begins when the atrial walls contract again
Coronary Arteries
Feed the heart and brings oxygen and nutrients to cardiac cells for aerobic respiration
Coronary Artery Disease
Fatty plaque builds up in the inner lining of coronary ateries - narrowing it (occlusion)
Blood flows is restricted which causes chest pain
Factors likely causing Coronary Artery Disease
- High blood cholesterol
- Smoking
- High blood
pressure (hypertension)
- High blood sugar
level (diabetes)
- Genetic
Atherosclerosis: Cholesterol builds up in damaged areas. This eventually forms plaque and the artery will lose its elasticity the lumen narrows restricting blood flow Cornary thrombosis: If the plaque raptures blood clotting is triggered. Blood clots are known as Cornary thrombosis
Athersclerosis can lead to blood clots. If these clots occur in myocardial tissue it is called Coronary Heart Disease
A myocardial infection (heart attack) occurs if the coronary artery becomes completely blocked
Coronary muscle tissue dies as a result of no oxygen and blood
Risk factors of Coronary Heart Disease:
- Genetic
Some people are predisposed for high cholesterol and blood pressure levels
- Age
Older people are more at risk because of less elasticity in arteries
- Sex
Males are at greater risk than females
- Smoking
Constricts blood vessels with increased blood pressure more platelets lead to more clotting
- Exercise
Lack of exercise increases risk because of weakened circulation
- Stress
Linked to increased cholesterol hormones in blood causing increased atherosclerosis
That's all, well done!
Drafted by Venetia (Biology)
References:
- https://www.google.com/url?sa=i&url=https%3A%2F%2Fmed.stanford.edu%2Fnews%2Fall-news%2F2020%2F06%2Funregulated-artery-cell-growth-may-drive-atherosclerosis.html&psig=AOvVaw36hyunli3v8yA7J29UXLFo&ust=1625665741808000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCKjoqvvKzvECFQAAAAAdAAAAABAU