Cardiovascular System Lecture 4 Flashcards
What leads to the opening and closing of valves?
Changes in pressure in atria, ventricles, and vessels leads to opening and closing of valves
Atrioventricular Valves
Atrioventricular (AV) valves are one-way valves in the heart that separate the atria (upper chambers) from the ventricles (lower chambers) and prevent the backflow of blood from the ventricles into the atria during the cardiac cycle.
There are two main AV valves in the heart: the tricuspid valve, located on the right side of the heart, and the bicuspid or mitral valve, located on the left side of the heart. These valves play a crucial role in maintaining the unidirectional flow of blood through the heart by opening and closing in response to changes in pressure as the heart contracts and relaxes.
Semilunar Valves
Semilunar valves are a pair of one-way valves located in the heart, specifically at the entrances to the main arteries leaving the heart—the aorta and the pulmonary artery.
Aortic Valve:
The aortic valve is situated between the left ventricle and the aorta, the largest artery in the body. It regulates the flow of oxygen-rich blood from the left ventricle into the aorta, which then carries blood to the rest of the body.
Pulmonary Valve:
The pulmonary valve is located between the right ventricle and the pulmonary artery. It controls the flow of oxygen-poor blood from the right ventricle into the pulmonary artery, which carries blood to the lungs for oxygenation.
Semilunar valves open and close in response to changes in pressure within the ventricles. When the ventricles contract (ventricular systole), the pressure inside the ventricles becomes higher than in the aorta or pulmonary artery. This pressure difference causes the semilunar valves to open, allowing blood to be ejected into the respective arteries. After ventricular contraction (ventricular diastole), when the ventricles relax and the pressure inside them decreases, the semilunar valves close to prevent blood from flowing back into the ventricles, maintaining one-way blood flow through the heart and into the circulation.
What is EDV?
End Diastolic Volume
What is ESV?
End Systolic Volume
How does the VENTRICULAR FILLING of the Cardiac Cycle Phase start? (4)
(DIASTOLE)
Phase Start (Left Ventricle Filling):
- The phase begins when the left atrium has a higher pressure than the left ventricle.
- This causes the bicuspid valve to open.
- During this phase, the left atrium contracts (atrial systole), pushing the last bit of blood into the left ventricle.
- At this point, the left ventricle is at its fullest volume, which is called end-diastolic volume (EDV).
How does the VENTRICULAR FILLING phase end?
Phase End (Start of Ventricular Systole):
The phase ends when the left ventricular pressure becomes higher than the left atrial pressure.
This pressure change leads to the closure of the bicuspid valve, which produces the first heart sound (S1 or “lub”)
How does the ISOVOLUMETRIC CONTRACTION of the Cardiac Cycle Phase start? (5)
(SYSTOLE)
Phase Start (Bicuspid Valve Closed):
- This phase begins when the bicuspid valve is closed.
- The left ventricular pressure is higher than the left atrial pressure.
- Simultaneously, the aortic valve is also closed because the left ventricular pressure is lower than the aortic pressure.
- During this phase, the left ventricle contracts (ventricular systole), but there is no change in the left ventricle’s volume.
- There is a rapid increase in left ventricular pressure.
How does the ISOVOLUMETRIC CONTRACTION phase end?
Phase End (Aortic Valve Opens):
This phase concludes when the left ventricular pressure becomes higher than the aortic pressure, causing the aortic valve to open.
How does the VENTRICULAR EJECTION of the Cardiac Cycle Phase start? (2)
(SYSTOLE)
Phase Start (Aortic Valve Opens):
- This phase begins when the aortic valve opens because the left ventricular pressure is higher than the aortic pressure.
- The left ventricle starts ejecting blood into the systemic circulation, initially rapidly and then more slowly.
How does the VENTRICULAR EJECTION Phase end?
Phase End (Aortic Valve Closes):
This phase ends when the left ventricular pressure drops below the aortic pressure.
The aortic valve closes, producing the second heart sound (S2 or “dub”), which is associated with the closure of the aortic valve.
At this point, the left ventricle is at its lowest volume, known as end-systolic volume (ESV)
How is the Ejected Volume Calculated?
(AKA Stroke Volume)
Difference between end-diastolic
and end-systolic volumes:
SV = EDV – ESV
(SV = Stroke Volume)
How does the ISOVOLUMETRIC RELAXATION of the Cardiac Cycle Phase start? (4)
(DIASTOLE)
Phase Start (Aortic Valve Closed):
- Aortic valve is closed because the left ventricular pressure is lower than the aortic pressure.
- Simultaneously, the bicuspid valve is also closed because the left ventricular pressure is higher than the left atrial pressure.
- During this phase, the left ventricle relaxes (ventricular diastole), but there is no change in the left ventricle’s volume.
- There is a rapid decrease in left ventricular pressure.
How does the ISOVOLUMETRIC RELAXATION Phase end? (2)
Phase End (Bicuspid Valve Opens):
- This phase concludes when the left ventricular pressure becomes lower than the left atrial pressure.
- This pressure difference causes bicuspid valve to open.
How does the VENTRICULAR FILLING of the Cardiac Cycle Phase start? (4)
Phase Start (Bicuspid Valve Opens)
- Bicuspid valve opens because the left atrial pressure > left ventricular pressure.
- Blood flows from the left atrium into the left ventricle, (starts rapidly and then more slowly).
- During this phase, the left atrium contracts (atrial systole), pushing the last bit of blood into the left ventricle.
- This marks the start of the next cardiac cycle, continuing the heart’s pumping action.
