Control of Cardiac Output in Systemic Circulation Flashcards
What happens to arterial and venous pressure when total peripheral resistance is decreased with no change to cardiac output?
Arterial decreases
Venous increases
What happens to arterial and venous pressure when total peripheral resistance is increased with no change to cardiac output?
Arterial increases
Venous decreases
What happens to arterial and venous pressure when cardiac output is decreased with no change to total peripheral resistance?
Arterial increases
Venous decreases
What happens to arterial and venous pressure when cardiac output is increased with no change to total peripheral resistance?
Arterial decreases
Venous decreases
Describe demand-led pumping
The heart responds to changes in arterial/venous pressure (key signals) which indicate the body’s need for blood.
Describe stroke volume
The difference between end diastolic volume and end systolic volume
How does vein pressure determine the end diastolic volume?
The pressure in the veins determines atrial pressure as there is no valve.
Blood passes from the atria to ventricles, causing the walls to stretch and pressure to rise.
Filling of the ventricles continues until the interventricular pressure is equal to that in the atria.
What is Starlings law of the heart?
Stroke volume is proportional to ventricular pressure, until the pericardium restricts filling.
What does the end systolic volume depend on?
Force of contraction
How hard it is to eject blood
What effect does noradrenaline have on the Starlings curve?
It will steepen the gradient as it improves contractility
Describe what is meant by contractility of the heart
It’s intrinsic ability to contract.
Changes in ability to produce force of contraction result from incremental degrees of binding between actin and myosin filaments.
What is ease of ejection of blood from the heart dependent on?
Aortic impedance (sum of external factors that oppose ventricular ejection) Total peripheral resistance (small effect)
Describe the Bainbridge reflex
High ventricular pressure sensed in the right atrium. Low parasympathetic activity increases heart rate but has no effect on force of contraction.
Describe pressure changes caused by eating a meal and how they are then returned to normal.
Increased activity of gut causes local vasodilation
TPR decreases causing venous pressure to increase and arterial pressure to decrease.
VP increasing causes CO to rise, and AP decreases causes increased heart rate and therefore CO.
Ventricular pressure reduced by extra pumping of the heart which increases atrial pressure.
If the heart rate alone was increased, describe the changes that occur.
CO increase, TPR remains the same
High CO decreases venous pressure and therefore stroke volume. CO returns to original value.