Overview of CV System and Cardiac Cycle Flashcards
What is diastolic pressure?
The lowest arterial pressure during ventricular diastole
What are the 3 primary components of the CV system?
Pump (heart)
Pipes (vasculature)
Fluid (blood)
Why is velocity low in the capillaries?
Favors exchange of diffusible substances between tissues and blood
- What are the 2 main circuits that are in series in the cardiovascular system?
- What is the type of flow in these circuits?
- The systemic circulation and the pulmonary circulation
- Pulsatile flow
The cardiovascular system can be simplified to be modeled as 2 pumps in [series or parallel].
Series
What is stroke volume?
The stroke volume is the total volume of blood ejected during systole. The volume in the heart is highest at the end of diastole and lowest at the end of systole. Thus, the stroke volume can be calculated as:
SV = End Diastolic Volume - End Systolic Volume
Why do we see a change from pulsatile flow to constant flow as we move from large to small vessels?
Pulsatile arterial blood flow and pressure changes, caused by the intermittent ejection of blood from the heart, are accommodated by the large elastic vessels and damped by a combination of two factors: distensibility of the large arteries and frictional resistance in the small arteries and arterioles
What are normal values for:
- Heart rate
- Stroke volume
- Cardiac output
- 60 - 90 bpm
- 70mL
- 5L / min
What role does resistance play in the CV system?
The CV system changes local resistances in order to control blood flow distribution
Systole begins with the […] of the […] valve and ends with the […] of the […] valve
Closing; AV valves
Closing; semilunar valves
Regions b and c on graph below
What is the EDV?
End diastolic volume - volume of blood in ventricle at end of diastole
How does Ohm’s law (V=IR) apply to the cardiovascular system?
What is the 2nd heart sound that is heard?
Dub –> closing of semilunar valves
What is the ESV?
End systolic volume - volume of blood remaining in the ventricle at the end of systole
During diastole the […] valves are open and the […] valves are shut.
Atrioventricular
Semilunar
In what order do electrical and mechanical events occur in the heart?
Electrical preceeds mechanical
What is the pulse pressure?
SBP - DBP
What is systolic pressure?
Usually referes to the highest arterial pressure during ventricular systole
In simple terms, how does the structure of large arteries differ from that of smaller arteries?
Larger = more elastic to accomodate pulsatile flow
Smaller = less elastic, more muscular, less compliant to regulate flow
Capillaries are a rolled tube of single cell endothelium –> needs to be thin to facilitate gas exchange
What is a normal ejection fraction?
55% - 70%
What is the EDP and ESP?
End diastolic pressure
End systolic pressure
The cardiovascular system allows for redistribution of […] volume of blood to different areas based on […]
Constant
Need
What is systole?
The contracting phase of the heart muscle. Begins when the atrioventricular valves close, which leads to isovolumic increase in pressure, followed by contraction
Describe the steps in the cardiac cycle from a mechanical perspective (not talking about electrical signals) for the left side of the heart.
Beginning of diastole:
Oxygenated blood from the pulmonary veins flow into the left atrium. Once the pressure in the left atrium exceeds that of the left ventricle, the bicuspid valve will open and blood will flow rapidly into the left ventricle during the rapid filling phase. During diastasis, blood flows more slowly from the pulmonary vein through the atrium into the ventricle resulting in an increase in pressure in the ventricle, atrium and veins. Finally, during atrial systole, the left atrium contracts to push the final amount of blood into the left ventricle (atrial kick). At this point, the left ventricle has reached EDV.
Beginning of systole:
At this point, rising pressure causes the bicuspid valve to close and the ventricle will experience an increase in pressure without an increase in volume (isovolumic contraction). This is driven by the muscle activation that is occuring due to electrical signaling. Ejection occurs when this increasing pressure in the left ventricle exceeds that of the pressure in the aorta, the aortic valve will open, the ventricle will contract, and the blood will be pushed from the left ventricle into the systemic circulation. The papillary muscles contract first during ventricular contraction to pull on the chordae tendinae to prevent bicuspid valve prolapse and back flow.
Describe the steps in the cardiac cycle from a mechanical perspective (not talking about electrical signals) for the right side of the heart.
Beginning of diastole:
Venous blood from the SVC and IVC flow into the right atrium. Once the pressure in the right atrium exceeds that of the right ventricle, the tricuspid valve will open and blood will flow rapidly into the right ventricle during the rapid filling phase. During diastasis, blood flows more slowly from the venous system through the atrium into the ventricle resulting in an increase in pressure in the ventricle, atrium and veins. Finally, during atrial systole, the right atrium contracts to push the final amount of blood into the right ventricle (atrial kick). At this point, the right ventricle has reached EDV.
Beginning of systole:
At this point, rising pressure causes the tricuspid valve to close and the ventricle will experience an increase in pressure without an increase in volume (isovolumic contraction). This is driven by the muscle activation that is occuring due to electrical signaling. Ejection occurs when this increasing pressure in the right ventricle exceeds that of the pressure in the pulmonary artery, the pulmonary valve will open, the ventricle will contract, and the blood will be pushed from the right ventricle into the pulmonary circulation. The papillary muscles contract first during ventricular contraction to pull on the chordae tendinae to prevent tricuspid valve prolapse and back flow.
How can you distinguish the aortic valve from the pulmonary valve just by looking at the valves themselves?
The aortic valve has two small openings on its lateral surfaces for the LCA and RCA
What is the 4th heart sound? What does it indicate?
Atrial kick
Indicates stiff ventricles, seen in older people and those iwth HTN
How does resistance vary with radius? What is the equation to describe this relationship?
As radius increases, resistance decreases
What is diastole?
Resting phase of heart muscle (usually referring to ventricles). This phase begins immediately following contraction of the ventricles and is the period of relaxation of the heart muscle. The atria and ventricles are filling during diastole.
How much blood is in the following circulatory structures at a given point in time:
- Pulmonary circulation
- Heart
- Systemic
- 9 - 10%
- 7%
- ~84%
- 64% venous
- 20% arterial
During systole, the […] valves are shut and the […] valves are open
Atrioventricular
Semilunar
What is the first heart sound that is heard?
“Lub” –> closing of AV valves
Describe the change in flow and pressure that occurs with transition from the small arteries to the arterioles.
Huge decrease in pressure
Flow becomes constant not pulsatile
How are flow rate, velocity, and cross-sectional area related?
Q = velocity * total cross-sectional area
In this equation, flow (Q) is constant. As such, velocity and cross-sectional area are inversely proportional. It is worth noting that the cross-sectional area referred to in this eqn is TOTAL CROSS-SECTIONAL AREA not cross-sectional area of the vessel (i.e. aorta vs. capillary). That explains why in the graph the cross-sectional area is largest for the capillaries not the aorta.
Diastole begins with the […] of the […] valve and ends with the […] of the […] valve
Closing; semilunar
Closing; AV valves
This is a PV loop for the ventricles. Label the diagram.
What is the mean arterial pressure?
DBP + (SBP - DBP)/3
Normal is between 90 and 93.3
What is the 3rd heart sound?
When can you hear it and its normal?
When can you hear it and its abnormal?
Normal sound heart during diastole after closure of semilunar valves
In people younger than 40
In older people
What are the general functions of the CV system?
- Transport and distribute gases, nutrients, wastes, signaling molecules, immune system components
- Regulate homeostasis (temp, fluid and electrolyte balance, adjust O2 and CO2)
What is the ejection fraction?
Stroke Volume / EDV
Measure of the contractility of the heart, how much total blood can it pump out with each beat relative to its maximum volume
Left ventricular pressure […] during systole and […] during diastole
Left ventricular volume […] during diastole and […] during systole
