Pressure And Flow In Systemic Circulation Flashcards
What is cardiac output?
Stroke volume x heart rate
What is total peripheral resistance?
The resistance of arterioles.
What is the advantage of arteries being distensible?
The stroke volume can pass through vessels during systole as they stretch and diastole as they recoil.
Arterial pressure rises in systole.
True or false?
True. Called systolic pressure.
Arterial pressure decreases in diastole.
True or false?
True. Called diastolic pressure.
What is the systolic pressure in an average male?
120 mmHg
What is the diastolic pressure in an average male?
80 mmHg
What is pulse pressure?
The difference between systolic and diastolic pressures.
What is the average pressure?
Diastolic + 1/3 pulse pressure.
Given an example of a resistance vessel in the cardiovascular system.
Arterioles and precapillary sphincters.
How do resistance vessels increase resistance?
They narrow the lumen of the vessel, restricting blood flow. They do this by contraction of smooth muscle in their walls.
What produces vasomotor tone?
The sympathetic branch of the ANS. Vasomotor tone is an equilibrium between vasodilatation metabolites and the sympathetic influence.
What does vasoconstriction cause?
An increase in resistance.
What does vasodilatation cause?
A lower resistance.
What are vasodilatator metabolite?
Extra point - give an example.
They cause vasodilatation when they are accumulated.
Extra point - H+ K+
What is reactive hyperaemia?
Extra point - give an example where this is normal.
When blood flow is lost, metabolites accumulate. This causes the arteries to expand so when blood flow is returned there is an enormous increase in blood flow for a short time as the resistance of the vessels is low. This causes the metabolites to be taken away with the blood flow so constriction occurs.
Extra point - when using a blood pressure cuff.
What is an advantage of auto regulation?
Tissues that are more metabolically active can personalise their blood flow.
What is auto regulation?
The supply pressure changes, so does the blood flow. This changes the metabolite concentration and therefore the resistance of the arteriole. Blood flow will return to the appropriate level for that tissues level of metabolism.
What conditions does auto regulation need to work?
The supply pressure needs to remain within specific limits so the tissues will take what they need.
What determines venous pressure?
Volume of blood in from the body and our via the heart.
What is central venous pressure?
The pressure in the great veins that fill the heart in diastole.
What does central venous pressure depend on?
Blood from the body, the hearts pumping, gravity and muscles pumping.
