Exam #2: Blood Pressure Regulation Flashcards
What is blood pressure?
Force exerted by the blood against any unit area of the vessel wall
Proportional to Flow x resistance
What is the equation for mean arterial pressure?
MAP= CO x TRP
Cardiac output x total peripheral resistance
Draw the arterial pressure waveform.
N/A
What is the effect of vasoconstriction?
Increased MAP Longer DBP (Diastolic runoff) & shallower Decreased capillary hydrostatic pressure pressure (because constriction is occurring upstream of the capillary, in the arteriole)
What is the effect of vasodilation?
Decreased MAP Shortened DBP (Diastolic runoff) & steeper Increased capillary hydrostatic pressure
What is pulse pressure?
SBP- DBP
Systolic blood pressure - diastolic blood pressure
How is MAP estimated?
(1/3 x Pulse pressure) + DBP
Review how blood pressure is measured.
1) Cuff inflation & listen to turbulent flow of blood through artery
2) Korotkoff sounds
- Not as accurate as direct cannulation
What are the determinants of pulse pressure? How are these augmented pathologically?
Stroke volume output
- PDA
- Aortic regurgitation
Compliance
- Arteriosclerosis
- Aortic stenosis
Systolic ejection
Does is pulse wave velocity measured clinically?
Compliance; the pulse wave is inversely proportional to compliance
Slow= compliant Fast= rigid
As the pulse wave travels down the blood vessel, what happens to the amplitude of the wave?
It gets bigger i.e. it is “amplified” thus, downstream pressure are greater than proximal pressures ?????
What does rigidity i.e. reduced compliance do to the amplitude of the pulse wave?
Intensifies it i.e. a larger amplitude= a less compliant aorta
What happens to the incisura as you compare arterial waveforms, traveling distally through the vascular tree?
The incisura occurs later in time
“Blip” that occurs from closure of aortic valve
What happens to the arterial waveform in regards to the amplitude as you travel down the vascular tree?
Dampen
Especially at the level of the arterioles
Why is it good to have large pressure drop-off at the level of the arterioles?
Protection of the capillaries distally
What happens to capillary hydrostatic pressure, resistance, & blood velocity (in the capillaries) with constriction of the arterioles?
Decreased capillary hydrostatic pressure
Increased resistance
Decreased blood velocity
What happens to capillary hydrostatic pressure, resistance, & blood velocity (in the capillaries) with dilation of the arterioles?
Increased capillary hydrostatic pressure
Decreased resistance
Increased blood velocity
Describe the distribution of CO at rest.
High percentage of cardiac output goes to:
1) Liver
2) Kidney
3) Muscles
4) Brain
What changes the distribution of cardiac output?
Demand
How is the distribution of cardiac output changed?
Local changes in arteriole resistance
What is autoregulation?
Maintenance of a stable blood flow, despite increasing arterial pressure
What are the mechanisms of autoregulation?
Metabolic mechanism
Myogenic mechanism
If there is an increase in pressure, what has to happen to resistance to maintain flow?
Increased resistance
What is EDRF?
Nitric Oxide
What is the effect of NO on arterioles?
Vasodilation
Describe the NO mechanism of action.
Inhibition of MLCK & activation of MLCP
Describe the bradykinin mechanism of action.
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What is the effect of endothelin?
Vasoconstriction
Describe the mechanism of action of endothelin.
Inhibition of MLCP
List some other vasoconstrictors.
NE
Angiotensin II
Vasoppressin
List the characteristics of short-term (acute) regulation of blood pressure.
- Minutes to seconds
- Change in resistance
- ANS reflex
List the characteristics of long-term regulation of blood pressure.
- Days to weeks
- Involves changes in volume
- Renal & hormonal mechanisms
What is the effect of sympathetic stimulation of the blood vessels? What is the receptor?
Vasoconstriction
alpha adrenergic recptor
What is the effect of sympathetic stimulation of the heart? What is the receptor?
Increased contractility, HR, & conduction velocity
Beta adrenergic receptor
What is the effect of sympathetic stimulation of the kidneys? What is the receptor?
Renin release (vasoconstriction via Angiotensin II) Decreased GFR (via vasoconstriction) Beta adrenergic receptor
What is the effect of sympathetic stimulation of the adrenal gland?
Epinephrine & NE release
What is the effect of PNS stimulation of the heart?
Muscarinic activation in SA & AV nodes leads to decreased HR
When the SNS is stimulated, where is there going to be the greatest change in vascular resistance? Where will the lowest change in vascular resistance be?
Greatest= cutaneous Smallest= renal
What is the effect of vasoconstriction of the arterioles? What is the effect of vasoconstriction of the veins? What is the net effect?
Arterioles= Increased vascular resistance, leading to decreased flow through tissue (more time for metabolism to occur)
Veins= increased venous return to heart
