The Heart 1.5 Flashcards
What is the equation for cardiac output?
Cardiac output= stroke volume x heart rate
What is the heart rate?
The number of heartbeats per minute.
What is stroke volume?
The volume of blood pumped during each heartbeat ( cm^3)
Cardiac muscle is said to be myogenic, what does this mean?
This means that it can contract and relax without receiving signals from nerves.
Outline the first step of the cardiac cycle in terms of pressure and volume.
Ventricles are relaxed. The atria contract, decreasing the volume of a chamber and increasing the pressure inside the chamber. This pushes the blood into the ventricles. There’s a sight increase in ventricular pressure and chamber volume as the ventricles receive the blood.
Outline the second step of the cardiac cycle in terms of volume and pressure.
The atria relax. The ventricles contract (decreasing their volume), increasing their pressure. The pressure becomes higher in the ventricles than the atria, which forces the AV valves to shut to prevent back flow. The pressure in the ventricles is also higher than in the aorta and the pulmonary artery which forces the SL valves to open.
Outline the third and final step of the cardiac cycle in terms of pressure and volume.
The ventricles and the atria both relax. The high pressure in the arteries means that the SL valves shut. The atria start to fill again due to the high pressure in the vena cava and pulmonary vein. This starts to increase the pressure in the atria, so the AL valves open again, which allows blood to flow passively to the ventricles without contraction.
What is an Atheroma and how does it form?
When damage occurs to the endothelium (by high blood pressure) white blood cells and lipids from the blood, clump together under the lining to form fatty streaks. Over time more build up to form fibrous plaque, Atheroma.
How do Atheroma’s increase the risk of an aneurysm?
An aneurysm is a balloon like swelling.
Atheroma plaques damage and weaken arteries. They narrow them increasing blood pressure. When blood travels through a weakened artery at high pressure, it may push the inner layers of the artery through the outer elastic layer, forming a balloon like swelling.
How do Atheroma’s increase the risk of thrombosis?
Thrombosis is the formation of a blood clot.
An Atheroma plaque damages the artery wall and leave a rough surface. Platelets and fibrin accumulate at the site of damage and form a blood clot. This can cause a complete blockage of the artery. Debris from the rupture can cause another blood clot to form further down.
Name three factors associated with coronary heart disease.
High blood cholesterol, poor diet
Cigarette smoking
High blood pressure
Name one factor of CHD that can’t be controlled.
A genetic predisposition to coronary heart disease
Having unnaturally high blood pressure as a result of another disease.
How does cigarette smoking effect the risk of CHD?
The carbon monoxide from cigarette smoking binds with haemoglobin instead of O2 so reduces the amount of oxygen transported around the body.
