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Physiology I: Cardiovascular System > Lecture 32: Arterial Pressure and Arterial System > Flashcards

Lecture 32: Arterial Pressure and Arterial System Flashcards

1
Q

Roles of arterial system

A
  • Primarily: distribute blood to capillary beds
  • Hydraulic filter
  • Arterial elasticity
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2
Q

Arterioles

A
  • Terminal components of this arterial system

- Regulate distribution of blood among the various capillary beds

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3
Q

Vessels between heart and arterioles

A
  • System of tubes

- Considerable volume and distensibility

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4
Q

Arterial system composed of

A
  • Elastic tubes with high resistance at the end

- “Hydraulic filter”

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5
Q

Hydraulic filter role

A
  • Converts pulsatile flow from heart to steady flow in capillaries
  • Minimizes workload of heart
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6
Q

Stroke volume enters arterial system

A
  • During diastole
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7
Q

Part of energy developed (or conveyed to blood as pressure) during systole is dissipated as

A
  • Forward capillary flow

- Rest (majority) is stored as potential energy in the walls of the arterial system

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8
Q

During diastole the elastic recoil of vessel walls

A
  • Converts potential energy into capillary blood flow
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9
Q

If walls were inelastic (rigid tubes)

A
  • No energy could be “stored” in walls and used to propel blood during diastole
  • Flow would cease during diastole in rigid tubes
  • 2x pressure would have to be developed for same flow in rigid tubes
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10
Q

Primary determinants (physical factors) of arterial blood pressure

A
  • Arterial volume

- Compliance of arterial system

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11
Q

Secondary determinants (physiological factors) of arterial blood pressure

A
  • Heart rate
  • Stroke volume
  • Cardiac output
  • Peripheral resistance
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12
Q

Mean arterial pressure (MAP)

A
  • Average pressure over time in aorta and large arteries
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13
Q

Formula for determining MAP

A
  • MAP = Pd + 1/3(Ps - Pd)
  • MAP = Pd + 1/3(PP)
  • (Ps - Pd) is pulse pressure (PP)
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14
Q

Pulse pressure

A
  • Essentially same factors that determine mean arterial pressure
  • Thus, stroke volume and arterial compliance determine pulse pressure
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15
Q

Increase in HR at constant Q results in

A
  • Decreased SV

- Deceased PP

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16
Q

Decreased TPR results in

A
  • Allowing rapid flow of blood from arteries to veins
  • Increased venous return
  • Increased SV as in exercise
  • Increased PP
17
Q

Increases in mean circulatory filling pressure (Pmcf) such as rapid transfusion blood volume results in

A
  • Increased SV

- Increased PP

18
Q

Sudden ejection vs. prolonged ejection

A
  • Sudden ejection increases PP more than prolonged ejection
19
Q

Atherosclerosis leads to

A
  • Decreased elasticity of arteries
  • Decreased compliance
  • Increased PP
20
Q

An increase in Pd is often used as indicator of

A
  • Changes in TPR

- Seen in hypertension (but not always the case)

21
Q

increase in TPR leads to an increase in

A
  • MAP (both Ps and Pd) if Q is unchanged

- But if there is concomitant decrease in Q by a decrease in SV, then MAP (Pd + Ps) may not be changed

22
Q

Radial stretch of aorta as blood is ejected from heart initiates

A
  • Pressure wave that is propagated down aorta

- Branches with finite velocity

23
Q

Peripheral arterial pressure curve/wave characteristics

A
  • Propagated wave is faster than forward movement of blood itself
  • Perceived when counting pulse rate
  • In aorta velocity of pressure wave may be 15 times that of blood flow
  • In more distal arteries, velocity of wave may be 100 times the velocity of blood flow
24
Q

Velocity of transmission of pressure wave varies inversely with

A
  • Vascular compliance

- Decreased vascular compliance (seen in more distal parts of arterial tree) leads to increased velocity

25
Q

Measurement of transmission velocity can be used to measure

A
  • Elastic characteristics

- Degree of compliance of arterial tree

26
Q

Three major things are seen as distortion of wave happens (wave moves more distally)

A
  • High frequency components of pulse (like incisura) dampen and disappear
  • Systolic portion becomes narrower and attains greater peak
  • A hump may become prominent in diastolic portion of pressure wave
27
Q

Narrowed and greater peak (augmentation) of systolic portion of wave occurs due to

A
  • Phenomena of reflection
  • Vessel tapering
  • Vessel resonance
28
Q

As wave travels to less compliant areas of arterial tree, the decreasing compliance causes

A
  • Retrograde or backward traveling wave of pressure

- Backward wave then summates with next forward moving wave, producing a higher wave (thus arterial augmentation)

29
Q

Retrograde augmentation of wave has little functional significance, but relates to

A
  • Blood pressures in peripheral arteries
  • Systolic pressure in peripheral arteries may be 20-30% greater than that of central aorta
  • Diastolic pressure may be reduced as much as 10-20% over aortic values

Physiology I: Cardiovascular System (12 decks)

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