Control Of Cardiac Output Flashcards
What happens if total peripheral resistance rises and cardiac output remains constant?
The arterial pressure will rise and the venous pressure will fall
What happens if cardiac output rises and the total periphral resistance remains constant?
Atreial pressure will rise and the venous pressure will fall
What happens if the cardiac output fall and the total peripheral resistance remains constant?
Atreial pressure will fall and the venous pressure will remain constant
How are changes in demand for blood met after a meal?
The gut needs more blood, so local vasodilators dilate the arterioles and the total peripheral resistance falls
Describe the proccess of demand led pumping.
If the body needs more blood, the heart needs to pump more
What is starlings law of the heart?
If the ventricle is stretched before contracting the heart contracts harder
How does starlings law happen?
Rises in venous pressure leads to a rise in stroke volume, and this fills the ventricles, causing them to stretch and therefore contract harder
Describe some of the features of the starling curve
Relates the stroke volume to the venous pressure, the slope is known as the contractility of the ventricle
What does how much the ventricle empty depend on?
How hard it contracts and how hard it is to eject blood
What determines the force of contraction?
The end distoolic volume and the contractility
How do you increase contractility?
Sympatheic activity to the heart
What is preload?
The volume of blood in the ventricles at the end of diastole
What is afterload?
The resistance the left ventricle must overcome to pump blood
How is the heart rate controlled?
The autonomic outflow is controlled by signals from the baroreceptors, and the carotid sinus sense the Aterial pressure, sends signals to the medulla which controls the heart.
What happens if there is a rise in venous pressure?
It is sensed in the right atrium, leading to reduced parasympatheic activity and a raise in the heart rate known as the Bainbridge reflex
How is a fall in aterial pressure contered?
Increase in heart rate by increasing the Sympatheic activity, and a increase in contractility by increasing the Sympatheic activity
What happens if total peripheral resistance falls and the cardiac output remains constant?
Aterial presure will fall and venous pressure will rise
What is the normal cardiac output of the heart and the output during excercise?
At rest, 5l/min, from 5-15 during excericse.
What are the different groups of baroreceptors found in the body?
The aortic arch, and the carotid body
What are the baroreceptors?
The major blood pressure sensors
What pressures of increase firing of the aortic arch?
Pressures> 100mmHg
What pressures increase firing of the cartoid body increase firing?
Pressures > 50mmHg
What is the normal blood pressure and what are the important features of the blood pressure?
It is 95mmHg, and this provides adequate pressure to perfuse and drive blood throug the CVS, there is a significant functional resevere available with many capillary beds not fully perfused, and if the blood presusre goes below 60 mmHg this can be singificaantly damaging to the CVS
What is the acute effect of standing up on the CVS?
Mean arterial pressure falls by 20-25mmHg by starlings law, with both the arterial and venous pressure falling acutely, and tis causes RA filling to drop which reduces the stroke volume of the heart.
