Control Of Cardiac Output (6) Flashcards
What are the four main components of the cardiac pressure system?
- Cardiac output
- Total peripheral resistance (TPR)
- Arterial pressure
- Venous pressure
How is venous pressure determined?
- Rate at which blood enters the veins
- Rate at which heat pumps blood out
What would happen to the arterial and venous pressure in the following cases?
- TPR increase, cardiac constant
- TPR decrease, cardiac constant
- Cardiac increase, TPR constant
- Cardiac decrease, TPR constant
- Arterial decrease, venous increase
- Arterial increase, venous decrease
- Arterial increase, venous decrease
- Arterial decrease, venous increase
What is TPR’s relation to the body’s need for blood?
- TPR is inversely proportional to the need for blood.
What is stroke volume?
- Difference between end diastolic and end systolic volume.
How does venous pressure effect the compartments of the heart?
- Ventricle fills until the wall stretched to the same extent as the venous pressure to create an equal intra-ventricular pressure.
What effect does venous pressure have on the heart’s volume?
- Higher the venous pressure the more the hart fills during diastole
- Ventricular compliance curve.
What is Starling’s law?
- The more the heart fills the greater the force of contraction (up to a limit)
- Harder the contraction, the greater the stroke volume
- So an increase in venous pressure will increase the stoke volume.
Describe the sterling graph.
- Y axis: stroke volume
- X axis: venous pressure
- Gradient: contractility
- Line: straight until starts to plateau then dip.
What does the amount of blood emptied out during systole depend on?
- Contractile strength
- How hard it is to eject the blood
What is the force of contraction determined by?
- End diastolic volume
- Contractility (increased by sympathetic activity)
What is aortic impedance?
- The harder it is to eject blood the higher the pressure rises in the arteries
What does aortic impedance depend on?
- Mainly TPR.
What change in arterial and venous pressure would result in an increase in stroke volume?
- Increased venous pressure
- Decreased arterial pressure
How is the heart rate controlled?
- Autonomic outflow to the heart controlled by signals from baroreceptors
- Carotid sinus senses arterial pressure
- Sends signals to the medulla -> control
