Flashcards in CVS- peripheral circulation Deck (45)
What is the function of arteries?
Gross conduction and distribution of blood supply
What is the function of arterioles?
Local distribution and fine control to defined tissue volume.
What is the function of capillaries?
Micro-diffusion and filtration.
What is the function of veins?
Collection, return and capacitance (reservoir).
What is compliance?
Ability of vessels to distend and increase volume due to pressure increase.
What is capacitance?
Effectively the same as compliance. It is a measure of relative volume increase per unit increase in pressure.
In which component of the CVS is the most blood found by volume at rest?
What is cardiac output?
Stroke volume x heart rate
How much is the normal cardiac output?
What is total peripheral resistance?
The sum of all arteriolar resistance.
What is the effect of compliance on the pulsatile pressure changes of systole and diastole?
Compliance acts to store mechanical energy or rising pressure wave in systole (by distension of elastic walls) and dissipates it more gradually over diastole )by recoiling of elastic walls). It therefore 'smooths out' the pressure wave.
Which arteries have the most compliance?
The aorta and elastic arteries with less smooth muscle/more elastin.
What is the Windkessel effect?
A term used to account for the shape of the arterial blood pressure waveform in terms of the interaction between the stroke volume and the compliance of the aorta and large elastic arteries (Windkessel vessels).
What is the systolic pressure?
The maximum major arterial pressure that occurs in systole.
What is diastolic pressure?
The minimum major arterial pressure that occurs in diastole.
Which vessels can be palpated for a pulse?
Arteries and large arterioles.
What factors affect systolic and diastolic pressure?
1. Cardiac output (SVxHR)
2. Arterial compliance (no SNS input to elastic arteries)
3. TPR (increase in TPR -> increase in arterial pressure)
What is the effect of ateriosclerosis in the elderly?
It decreases the compliance of arteries and therefore increases blood pressure, causing hypertension.
What is the pulse pressure?
Systolic pressure - diastolic pressure
How would you calculate average pressure?
Diastolic pressure + 1/3 of pulse pressure
How much time on average is spent in diastole compared to systole?
0.55s compared to 0.3s
What causes the decrease in pulse pressure?
Summated resistance and capacitance of arteriolar network.
What happens if there is not enough pressure for blood to flow through the capillaries?
List the resistance vessels of the circulatory system:
Arterioles and pre-capillary sphincters
How do arterioles and pre-capillary sphincters create high resistance?
They narrow the lumen by contraction of the proportionally large amount of smooth muscle in their tunica media.
What governs the blood flow to capillary beds?
Arteriolar vasomotor tone
What two opposing control elements work together to finely regulate vasomotor tone, to very small tissue volumes?
Regulation of vasoconstriction and vasodilatation.
Why is it important to regulate blood flow to capillary beds?
In order to precisely match substrate supply to metabolic demand.
What factors govern the high arteriolar vasomotor tone at rest?
Mostly centrally controlled by autonomic SNS (circulating hormones modulate):
1. Release of NA acts on alpha-1-GPCRs -> [Ca2+]i contraction.