The heart and disease Flashcards
Describe how atheroma may form and lead to a myocardial infarction (6)
Cholesterol deposited in the artery wall This atheroma narrows lumen of the artery This creates turbulence and can damage to lining of artery Turbulence increases risk the of blood clot (thrombus) The blood clot may break off (embolus) And lodge in coronary artery; Reduced blood supply to heart muscle; Reduced oxygen supply; Reduced respiration Leads to death of heart muscle
What is the mechanism of the heart beat? (6)
Cardiac muscle is myogenic The SAN Sends a wave of electrical activity (depolarisation) across the atria This triggers atrial systole The impulse is relayed to the ventricles through the AVN Passing down to the apex of the heart along the bundle of His The impulse spreads along the ventricle walls via the purkyne fibres The ventricles contract from the bottom The AVN delays ventricular systole to allow them to fill up with blood
Why is the wall of the left ventricle thicker than the right?
The left ventricle has a thicker, more muscular wall than the right ventricle as it has to pump blood around the whole body, so must generate a higher pressure.
What is cardiac output?
Cardiac Output: is the amount of blood flowing through the heart each minute. It is calculated as the product of the heart rate and the stroke volume: Cardiac output = heart rate x stroke volume
What is the stroke volume. Can it be varied?
The stroke volume is the volume of blood pumped in each beat. Both the heart rate and the stroke volume can be varied by the body. When the body exercises the cardiac output can increase dramatically so that • Oxygen and glucose can get to the muscles faster • Carbon dioxide and lactate can be carried away from the muscles faster • Heat can be carried away from the muscles faster
When do we hear the familiar lub dup heart beat and why? (4)
When ventricular pressure > atrial pressure (1) the atrioventricular valves shut to prevent backflow, this is the first sound in the heart beat (lub) When the ventricular pressure < arterial pressure (3) the semilunar valves shut, this is the second sound of the heart beat (dup)
What are valves for?
Valves in the heart and blood vessels (mainly veins) prevent back flow
Where are the biscuspid and tricuspid valves? (AV valves)
Tricuspid valve is on the right side of the heart Bicuspid valve is on the left side of the heart
Where do we find the semi-lunar valves?
Semilunar valves are located between the ventricles and the aorta and pulmonary artery. Rare for arteries to have valves
What sort of blood is carried in the pulmonary artery and where does it go?
Pulmonary artery carries deoxygenated blood to the lungs. Rare for arteries to carry deoxygenated blood
What sort of blood is carried in the pulmonary vein and where does it go?
Pulmonary vein carries oxygenated blood to the heart from the lung, rare for vein to have oxygenated blood.
What is double circulation?
Double circulation: blood flows through the heart twice for one circuit of the body, needs re-pumped after losing pressure in the lungs
Where is the SAN?
The wall of the right atrium
What is it called when parts of the heart contract?
Systole
What is it called when parts of the heart relax?
Diastole
