Cardio 7 Flashcards
Different cardiac ____ have different ____ at different _____
cells
permeabilities
times in the heart cycle
What drives a slow action potential (SA and AV node)?
The calcium gradient
In a fast AP, K+ is permeable during:
Options: resting potential, upstroke, plateau, repolarization
the resting potential
upstroke
repolarization
In a fast AP Na+ is permeable during:
Options: resting potential, upstroke, plateau, repolarization
Upstroke
In a fast AP Ca+ is permeable during:
Options: resting potential, upstroke, plateau, repolarization
Plateau
In a slow AP K+ is permeable during:
Options: pacemaking, upstroke, plateau, repolarisation
pacemaking
repolarization
In a slow AP Na+ is permeable during:
Options: pacemaking, upstroke, plateau, repolarisation
a bit in the pacemaking
In a slow AP Ca+ is permeable during:
Options: pacemaking, upstroke, plateau, repolarisation
upstroke
plateau
Starting from the atrial and ventricular diastole, what are the steps of a cardiac cycle? (5)
- Atrial and ventricular diastole
- Atrial systole
- Isovolumic ventricular contraction (AV valve closes)
- VEntricular systole
- Isovolumic ventricular relaxation
What happens to ventricular volume during atrial systole? What about ventricular pressure?
Volume increases since blood is being pushed from the atria into the ventricles
Pressure increases with the atrial pressure while staying below it to maintain a pressure gradient towards the ventricle
What happens to ventricular volume during isovolumic ventricular contraction? What about ventricular pressure?
It stays the same, the AV valve is simply closing
As the AV valve shuts, the ventricular pressure increases drastically because the heart contracts, but both valves are closed
What happens to ventricular volume during ventricular systole? What about ventricular pressure?
It decreases to reach the aorta or pulmonary trunk.
Pressure increases until it is greater than in the great vessel. The semilunar valve opens, the ventricular pressure stays over aortic pressure to have a pressure gradient towards the aorta, the aortic pressure starts tracking ventricular until ventricular drops drastically
What happens to ventricular volume during early ventricular diastole? What about aortic pressure?
The semilunar valves close. The atrias have been slowly filling, the AV valves open, and there is a small amount of blood that enters the ventricle.
The aortic pressure stays the same thanks to the Windkessel effect
What happens to ventricular volume during late diastole? What about ventricular pressure?
There is a slow increase to reach the atrial systole volume
Ventricular pressure will remain under atrial pressure to have a pressure gradient
When will the aortic and pulmonary valves close? why?
They will close as soon as ventricular pressure drops under aortic/ pulmonary pressure to ensure that there is no back flow due to an inverse pressure gradient
What is pulse pressure?
The difference in maximum and minimal pressure in the aorta
What explains that the aortic pressure never drops to zero even if there isn’t always blood being pumped by the ventricles?
The Windkessel effect: maintaining the pressure in the systemic circulation during the relaxation phase
Explain how the Windkesel effect works in the heart
When the aorta expands during a heartbeat, the elastic walls allow energy storage. When the ventricles stop pumping blood and the aortic valve shuts, the aortic walls release the stored energy (recoil) to keep a continuous flow
What would be the consequences of blood vessels losing their recoil property?
The systole pressure would increase, and the diastole pressure would decrease, resulting in a bigger pulse pressure. This can increase CV risk, and the heart has to work harder (can hypertrophy left ventricle (not good))
Try thinking of all the pressure and volume changes as they relate to an ECG reading.
see slide 29 of L7 if needed
What are the 3 indirect methods of measuring blood pressure?
Palpitation
Auscultation
Oscillation
What are the main features of the cuffs used in all indirect methods of measuring blood pressure?
They can be inflated around an arm to the point where blood flow is obstructed. These cuffs have a measurement mechanism attached that gives a reading of the pressure in the cuff and a valve that allows for controlled, slow reduction in cuff pressure.
What is palpitation blood pressure measurement?
Measure the presence of a pulse at the wrist using your fingers. A cuff is inflated until the pulse can no longer be felt. At this point, the pressure in the cuff exceeds that of the radial artery. The pressure in the valve is slowly released. As soon as the pulse is felt, this gives a measure of the systolic pressure.
What is useful during auscultation blood pressure measurement?
the transition from laminar to turbulent flow.
What is auscultation blood pressure measurement?
The cuff constricts the artery, so there is a sudden expansion just after the cuff where turbulent flow occurs. This turbulent flow can be heard using a stethoscope (systolic pressure). You can hear these sounds until flow becomes laminar again, indicating a measure of the diastolic pressure
What is the sound made by turbulent flow?
These sounds are called Korotkoff sounds after Nikoli Korotkov
Why can we say that laminar flow (no more sound heard) after the cuff constriction indicates diastolic pressure?
the pressure in the artery is now always high enough to ensure laminar flow, even at the lowest pressure point in the cardiac cycle.
What is oscillometry blood pressure measurement?
This is what all automated blood pressure machines use, with the same principles as the other indirect methods.
