2000 : Pathophysiology Flashcards
What is the first phase of the cardiac cycle?
Atrial contraction :
When oxygenated blood enters the left atria (LA), passes through the mitral value and into the left ventricle (LV)
- the pressure in the LA is greater than the LV hence blood flows nicely into LV to reach 80 % pressure filling.
- aortic valve is closed
What is the second phase of the cardiac cycle?
Isovolumetric contraction
- once the pressure in the LV exceeds the pressure of the LA the mitral valve closes
- this triggers the LV to being to contract lifting the LV pressure to 79 %
- the LA is still being filled with oxygenated blood
What is the third phase of the cardiac cycle ?
Rapid ejection
- LV contracts beyond the pressure of the aorta forcing the aortic valve to be opened (79 - 120 )
- the pressure within goth LV then translates to the aorta
- in the beginning of this phase the aorta expands slightly due to the rapid ejection of the blood within the LV
What is the fourth phase of the cardiac cycle ?
Slow ventricular ejection
- the LV is beginning to relax hence blood flow is at a slow pace entering the aorta via the aortic valve
What is the fifth phase of the cardiac cycle ?
Isovolumetric relaxation
- LV is relaxed and into a diastole phase
- LV pressure is lower than aortic pressure hence aortic valve closes
- LV pressure is still above LA pressure hence mitral valve is still closed
What is phase six of the cardiac cycle
Rapid passive ventricular filling
- pressure in the LV has gone below the pressure in the LA
- mitral valve is open
- oxygenated blood rapidly fills the LV with 80% pressure
What is phase 7 of the cardiac cycle ?
Slow passive ventricular filling
- blood is slowing filling the LV from the LA
- aortic valve is still shut
- LA contraction occurs to gain the last 2 % of oxygenated blood from the LA
What is EDV
The blood left in the heart after relaxation
What is ESV ?
The blood remaining in the heart after contraction
Draw a diagram to describe the flow of blood through the heart
SVC + IVC -> RA (tricuspid valve) RV (pulmonary valve) lungs -> LA (mitral valve) LV (aortic valve) aorta
What is an ejection fraction? And what is the normal functioning capacity ?
The percentage of the total amount of blood that is pumped out in each heartbeat
65%
Ejection fraction equation
EF = SV
——-
EDV
Define
- Inotropic
- Chronotropic
- Dromotropic
Inotropic - increasing the force on contractions
Chronotropic - increasing heart rate
Dromotropic - increasing the speed of conduction
Why is cardiac output equal on both side but there is a pressure difference for both left and right sides of the heart
When cardiac output is equal on both sides of the heart the pressure of each side is not equal because the right side has to overcome the pressure of the lungs and the left side needs to supply the rest of the body with blood hence pressure is different. Therefore Cardiac workload is not equal in equal sides if the heart
What is preload and what can influence it ?
the amount of blood returning to the atria
Influenced by ; GTN, anaphylaxis, dehydration, posture, haemorrhage decrease preload
What is afterload and what can it be influenced by ?
pressure the heart has to pump against to get blood back out into the body
Influenced by ; Vasoconstriction, adrenaline, aortic stinosis (thick aorta) will increase after-load
The main reason myocardial contractile cells can stimulate depolarization of adjoining cells is via what mechanism?
Gap junctions are bridges between the cell membranes
What area of the body does blood flow through ?
Blood flows from areas of high pressure to areas of low pressure
What effect would a positive inotrope have on the heart?
It would increase the stroke volume
A patient has a heart rate of 150bpm. What effect would a positive chronotrope have?
Reduced preload due to reduced ventricular filling time
During isovolumetric contraction the atria are in diastole and the ventricles are in systole
True or False
TRUE
How do cells become excitable?
Cells become excitable by the feature that the gap junctions relay allowing the leakage of sodium through one cell into another and so on therefore creating a large cell stimulus.
ONLY IN DEPOL
REPOL DOES NOT HAVE GAP JUNCTIONS
they flow like a river from the epicardial surface of the myocardium towards the endocardial surface. What are these rivers called ?
Coronary arteries
When will the aortic valve open
The pressure within the left ventricle exceeds the pressure within the aorta
Name the four coronary arteries
- Left coronary artery
- Circumflex artery
- Left anterior descending artery
- Right coronary artery
What is cardiac ischaemia ?
It is the lack of blood supply to a certain area, causing the delay in the depolarisation and depolarisation of the cardiac cells.
Can be detected through ST depression and inverted T waves
What is cellular infarct ?
Irreversible injury cause it cell death
Can be detected through ST depression and T wave inversion
