The Heart Flashcards
(45 cards)
Name the 3 main stages of the cardiac cycle in order
- Atrial systole
- Ventricular systole
- Diastole
Describe atrial systole
The atria contract creating an increase in pressure and a decrease in volume. Pressure increases above that in the ventricles forcing the AV valves to open and push blood into the ventricles.
Describe ventricular systole
The ventricles contract at the base of the heart, increasing ventricular pressure and decreasing ventricular volume. Pressure increases above that in the atria forcing the AV valves to close to prevent back-flow. The semi-lunar valves open to push blood out of the heart.
Describe diastole
The atria and the ventricles relax. The semi-lunar valves are shut by the pressure in the aorta and pulmonary artery. Blood begins to fill the atria as the pressure here is less than the pressure in the vena cava. Some blood passively flows into the ventricles.
What is the key function of valves in the heart?
To ensure blood flows in the right direction and prevent backflow
Where are the atrioventricular valves located?
Between the atrium and ventricle
Where are the semi-lunar valves located?
Between the atria and the arteries
Describe the opening of the semi-lunar valves
When ventricular systole takes place, the pressure in the ventricle exceeds the pressure in the arteries, causing the semi-lunar valves to be pushed open
Why do humans have a double circulatory system?
It is made of the pulmonary circulation between the lungs and heart, and the systematic circulation between the heart and the rest of the body
What is cardiac output?
The volume of blood pumped by the left ventricle in one minute. I.e, stroke volume X heart rate
Explain three risk factors of CHD
Smoking produces CO which binds irreversibly to haemoglobin, reducing the vol of O2 that can be carried to heart. Nicotine is a vasoconstrictor so increases blood pressure. Tar can increase viscosity of blood. Stress increases blood pressure. High blood pressure leads to hardening of blood vessels as it increases rate at which cholesterol is deposited. Diets high in sat fats increase LDL levels. More plaques
What is the name of the inner lining of blood vessels?
The endothelium
What is the advantage of blood vessels being lined with smooth endothelium?
It reduces friction with moving blood
Moving outwards, describe the structure of a blood vessel
Endothelium, elastic fibres, smooth muscle, collagen
What is the function of the elastic fibres in blood vessels?
To stretch and recoil to provide flexibility
What is the function of the smooth muscle in blood vessels?
To contract and relax to change the size of the lumen
What is the role of collagen in blood vessels?
To provide structural support which maintains the shape and volume of the vessel
Do arteries carry blood away or towards the heart?
Away
Do arteries carry blood at high or low pressures?
High pressures, arteries are thick to withstand this pressure
Do arteries have a wide or narrow lumen and why?
Narrow, to maintain high pressure
Why do arteries have a folded inner wall?
To allow the lumen to expand as blood flow increases
What is the role of elastic fibres in arteries and when do they return to their normal shape?
To stretch and recoil to help maintain blood pressure and they return to their normal shape in between heart contractions
What is the role of smooth muscle in arteries?
To allow vasodilation and vasoconstriction to take place in response to the need for blood in particular organ
What are arterioles?
Small blood vessels that distribute blood from arteries to capillaries
