T3 L9: The cardiac pressure-volume cycle Flashcards
What is the circle of Willis?
Arteries on the inferior brain organised in a circle that provide a redundancy of blood flow
What % of cardiac output goes to the kidenys?
20-25%
Which organ produces ACE, Erythropoietin, and Renin?
The kidneys
What does adrenergic input do to skeletal muscle circulation?
Vasodilatation because muscles are associated with the fight or flight response
What are the 4 sequential events of the cardiac cycle?
- Ventricular filling
- Isovolumic ventricular contraction (Pressure is created but there is no actual contraction)
- Ejection (actual contraction)
- Isovolumic ventricular relaxation
What is a Wiggers diagram?
A cardiac diagram used to teach physiology
What is the Dicrotic notch?
A dip in a cardiac diagram indicating the closure of the aortic valve. It happens after ejection
What is S1 on a cardiac diagram?
The Lup sound. It indicated the mitral valve closing during isovolumic contraction
What is S2 on a cardiac diagram?
The dub sound. Isovolumic relaxation
When does the aortic valve open?
After isovolumic contraction (when the heart fills up). With a health heart, there wont be a sound made
When does the mitral valve open?
At the end of isovolumic relaxation (when the heart is empty)
When does the P wave occur?
Right before the heart starts filling
On a pressure-volume loop, describe where Ejection, Isovolumic relaxation, Isovolumic contraction and Filling are
IVR, ejection, IVC and filling in a clockwise direction
What does a pressure-volume loop look like with mitral stenosis?
Decreased preload and decreased afterload. The whole loop will be to the left because there is a lower volume of blood.
What is mitral stenosis?
A narrowing of the mitral valve opening
What does a pressure-volume loop look like with aortic stenosis?
Increased afterload. The aortic valve is partially closed so its much harder to pump blood out therefore the left ventricular pressure is great
What is aortic stenosis?
A narrowing of the aortic valve opening
What does a pressure-volume loop look like with mitral regurgetation?
High preload and decreased afterload. The is never a point when the mitral and aortic valves are fully closed so the whole diagram looks like a side ways oval
What is mitral regurgitation?
The mitral valve doesn’t close
What does a pressure-volume loop look like with aortic regurgitation?
Increased preload. The diagram is liver shaped.
What is aortic regurgitation?
The aortic valve doesn’t close
What is a phonocradiagram?
The heart sounds
Which of the 2 heart sounds is louder?
The first (S1)
What causes a murmer?
Turbulence
What causes a systolic murmur?
Fluid leaving the ventricle. Eg. during AV regurgitation or SL stenosis
What causes a diastolic murmur?
Fluid entering the ventricle. Eg, during AV stenosis or SL regurgitation
What is the think filament made out of?
Actin
What is the thick filament made out of?
Myosin
Why is the cardiac action potential longer?
Because Ca2+ and K+ flow during the plateau phase and this doesn’t happen in neural action potentials
What are nodal action potentials based on?
Flow of Ca2+
How do delayed rectifier K+ channels work?
They open when the membrane depolarises but gating happens after a delay
How do inward rectifier K+ channels work?
They open when the Vm gets below -60 mV( most cells open at rest). They clamp the membrane firmly at rest and allow repolarisation
At what mV does a cell normally rest?
-70 mV
What happens during depolarisation?
The cell becomes less negative (more positive)
