CVS Session 6 (Lecture 6.1) Flashcards
What factors increase arterial pressure and determine it?
Increased cardiac output and increased TPR
What factors determine pressure in veins?
Rate at which blood enters and rate at which heart pumps it out
What occurs if CO remains constant and TPR falls to arterial and venous pressure?
AP - Falls
VP - Increases
What occurs if CO remains constant and TPR rises to arterial and venous pressure?
AP - Increases
VP - Falls
What occurs if TPR remains constant and CO rises to arterial and venous pressure?
AP - Increases
VP - Falls
What occurs if TPR remains constant and CO falls to arterial and venous pressure?
AP - Falls
VP - Increases
What is TPR inversely proportional to?
Body demand for blood
What is meant by demand-led pumping? How is it expressed?
If the body needs more blood, the heart pumps more to meet the demand.
Expressed as changes in arterial and venous pressure
What is stroke volume the difference between?
End diastolic volume - End systolic volume
remember heart fills in diastole
What is the intra-ventricular pressure equal to? Explain?
Equal to venous pressure as during diastole the ventricles fill, so are reliant on the venous pressure. The higher the venous pressure the more the heart fills.
Describe the ventricular compliance curve? Draw it out.
Relationship between venous pressure and ventricular volume.
What is Starling’s law?
The more the heart fills in diastole, the harder it contracts so the bigger the SV as the ventricular walls are stretched.
Rises in VP lead to increased SV
What is the Starling curve? Draw it
Relates SV to venous pressure
Slope is the contractility of the ventricle (not same as FOC)
What occurs at the top, flat portion of the graph?
Heart cannot stretch anymore due to pericardium holding the heart in place. This decreases the FOC
What affects the end systolic volume?
How hard the heart contracts
How hard it is to eject
What determines the FOC? How is contractility increased?
End diastolic volume and contractility
Increased by sympathetic activity
If it is harder to eject blood into the arteries what will the AP do?
Rise
If it easier to eject blood in systole, what occurs to AP, ESV and SV
AP - falls
ESV - falls (systolic volume)
SV - increases
What occurs to SV if VP rises or AP falls?
Increases (VP is the dominant variable)
Where is the carotid sinus? What exists there and where does it sends signals to?
At the bifurcation between the internal and external carotid arteries.
Baroreceptors to medulla controlling HR
If arterial pressure falls how does the carotid sinus respond?
Senses fall in AP therefore increases HR by increasing sympathetic and decreasing parasympathetic sactivity to the heart.
Increases contractility by increasing sympathetic activity.
If venous pressure falls how does the heart respond?
Increased VP Sensed in RA Lead to reduced PS activity Rise in HR Bainbridge reflex
