The Heart - A4 Flashcards
What type of system is the heart in mammels?
Double circulatory system
What is the first of the two circulatory systems?
Deox. blood moves through the heart and is pumped to the lungs, returning back to the heart (pulmonary circulation)
What is the second of the two circulatory systems?
Blood returns to the heart(the blood is repressurised) and pumped round the body organs before returning to the heart (systematic circulation)
Where does deoxygenated blood enter the heart from?
Enters through right atrium so would come from body going to the lungs.
Where are the atrio-ventricular valves?
Between the right atrium and right ventricle (same on the left)
Where are the semi-lunar valves?
Between the ventricles and arteries
How have the ventricles been adapted?
Thicker muscular wall than atria so can push blood out of the heart(atria push blood to the ventricles)
How has the left ventricle been adapted?
Thicker, more muscular wall than right. Provides more powerful contraction and pump blood all around the body (right only pumps into lungs)
What is the function of the atrioventricular(AV) valves?
Stop blood flowing from the ventricles back into the atria
What is the function of the semi-lunar valves?
Stop blood flowing back into the ventricles after they have contracted
What is the function of the cords?
They attach the AV valves to the ventricles to stop them being forced up into the atria when the ventricles contract
What is the function of heart valves in general?
-ensure that the blood flows in one direction only through the heart
-these valves will only open in one direction
-they open and close due to pressure differences on either side of the valves
What is the cardiac cycle?
An ongoing sequence of contraction(systole) and relaxation(diastole) of the atria and ventricles - 3 stages
What is Atrial systole (stage 1 of the cardias cycle)?
-atrial muscle wall contracts
-decreases volume of the atria
-pressure of the blood is higher in the atria then the ventricles
-blood is forced from the atria into the ventricles via pressure gradient
-atrio-ventricular valves opens to allow blood through
What is ventricular systole( stage 2 of the cardiac cycle)?
-ventricular muscle wall contracts( atria muscles relax)
-decreases volume in the ventricle
-blood pressure in the ventricle is higher than in the arteries
-blood forced from the ventricles into the arteries via the pressure gradient
-semilunar valves open to allow blood into the arteries
-atrioventricular valves shut to prevent backflow into the atria
What is diastole(stage 3 of the cardiac cycle)?
-both atria and ventricular muscles relax
-volume of ventricle increases so pressure decreases
-semilunar valves shut to prevent backflow
-atria fill again due to higher pressure in vena cava and pulmonary vein
-pressure in ventricles fall below the atria causing blood to flow passively through the AV valve into the ventricle
How do you calculate cardiac output?
cardiac output=stroke volume x heart rate
What is heart rate?
The no. of beats per minute (bpm)
What is stroke volume?
The volume of blood pumped during each heartbeat, measured in cm^3
What is cardiovascular disease?
-a general term used to describe disease associated with the heart and blood vessels
What are some examples of cardiovascular diseases?
aneurysms, thrombosis, myocardial infarction, and coronary heart disease
What do most cardiovascular diseases start with?
Most start with an atheroma
What is an atheroma?
fatty material under the endothelium lining of the artery. It is a fibrous plaque.
How do atheromas form?
-If the endothelium is broken(high blood pressure), cholesterol and fatty material clumped together under endothelium lining of an artery start to form fatty streaks
-over time this builds up continues and forms a fibrous plaque called an atheroma
-atheromas partially block the lumen and restrict blood flow(BP increases)
What causes thrombosis?
-formation of a blood clot and starts with the formation of an atheroma
-atheroma plaque ruptures the endothelium, leaving a rough surface
-platelets and fibrin accumulate on the rough surface and form a blood clot(thrombosis)
-this can cause a complete blockage of the artery and block a blood vessel elsewhere
What causes an aneurysm?
-when arteries become narrow or blocked, blood pressure increases
-when blood at high pressure travels through a weakened artery, the blood can push the inner layer through outer elastic layer
-aneurysms may burst, causing haemorrhage
What is myocardial infarction and how is it caused?
-Heart muscle is supplied with blood by the coronary arteries(stress more)
-if the artery becomes blocked(by a thrombosis/atheroma), oxygen needed by the heart muscle will not be delivered
-heart muscle cells will mot be able to respire aerobically and ultimately die- causing a myocardial infarction
What is the purpose of the coronary arteries?
Supply glucose and oxygen to heart muscles through the blood
What happens if there is a partial blockage in the blood vessels?
(angina)
partial blockage>muscle cells deprived of sufficient oxygen>the cells respire anaerobically>produce lactic acid>angina
What are the three risk factors for CVD?
high blood pressure, high blood cholesterol and poor diet, cigarette smoking
What is the risk factor of high blood pressure?
not exercising, overweight> high BP> atheroma formation>blood clots>myocardial infarction
What is the risk factor of high blood cholesterol and poor diet?
1) diet high in saturated fat>high blood cholesterol>atheroma formation>blood clots>myocardial infarction
2)diet high in salt>high blood pressure>atheroma formation>blood clots>myocardial infarction
What is the risk factor of cigarrette smoking?
1)smoking>carbon monoxide>less oxygen in blood>less oxygen to tissue>myocardial infarction
2)smoking>fewer antioxidants>damage to coronary artery walls>atheroma formation>myocardial infarction
