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Organ Systems > Vascular pt 2 > Flashcards

Vascular pt 2 Flashcards

0
Q

Transmural (intravascular) pressure

A

• The ΔP between the intravascular (inside) and tissue (outside) pressure

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1
Q

explain Perfusion (driving) pressure

A
  • The ΔP between arterial and venous ends of a blood vessel

* Generated by contracting heart and elastic arteries.

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2
Q

Wall distension depends on

A

compliance.
• Veins expand easily to store blood because of high
compliance and low transmural pressures. (These two are determined by CO & R)

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3
Q

explain Gravity (hydrostatic) pressure

A
  • ΔP is proportional to the height of the column of blood in the body; exists in absence of blood flow
  • Pressure lowest in head, highest in feet
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4
Q

3 BLOOD PRESSURE CHARACTERISTICS

A

Perfusion (driving) pressure
Transmural (intravascular) pressure
Gravity (hydrostatic) pressure

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5
Q

TRANSMURAL PRESSURE (P) generates stress (S) within wall; it is a function of

A

radius (R) and wall thickness (w). Based on LaPlace equation: T=PR and S=T/w. • S = P x R/w
• Vessels that produce little stress and can tolerate high pressures are
– small vessels eg. capillaries (low R)
– thick walled vessels eg. aorta (large w)

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6
Q

characteristics of Perfusion pressure are ?

A

directed along the length of the vessel (kinetic energy)
• Important pressure for direction O2 and nutrients to tissues
• Not affected by change in radius

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7
Q

characteristics of Transmural pressure?

A

directed against the wall (potential energy)

• Important in smoothening pressure pulses.

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8
Q

According to Bernoulli’s principle: Perfusion & transmural pressures vary with velocity of flow, why?

A

– Increased velocity decreases the lateral, transmural pressure thus, more fluid energy is in the form of forward kinetic energy, and less as sideways, potential energy.

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9
Q

– In dilated vessels, there is more ___ and is potentially dangerous in aneurysms

A

transmural (lateral) pressure

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10
Q

Pressure gradient (ΔP) across a blood vessel depends on its

A

resistance.

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11
Q

Aorta has high pressure due to ?

A

cardiac output and low compliance of aorta.

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12
Q

Arterioles form the largest drop in pressure (ΔP) across the vascular system due to ?

A

high resistance.

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13
Q

Capillary pressure drops due to ?

A

friction and outward filtration of fluid

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14
Q

Venules & Veins: pressure decreases with increased ?

A

compliance

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15
Q

Blood pressure is a key index of CV health, since it can reflect changes in ?

A

cardiac output (CO) and total peripheral resistance (TPR).

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16
Q

___ is the average pressure in a cardiac cycle.

A

Mean Arterial Pressure (MAP)
Diastolic P + 1/3 (systolic - diastolic pressure)

MAP rises with either increased CO or TPR.

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17
Q

MAP rises with either increased

A

CO or TPR

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18
Q

____ is the difference between systolic and diastolic pressures.

A

Pulse pressure

• PP=Ps-Pd

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19
Q

____ is proportional to stroke volume (SV) and inversely proportional to compliance (C)

A

Pulse Pressure

• PP = SV / C

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20
Q

Stretch-ability” of blood vessels walls; it is the inverse of elasticity (resistance to stretch).
Dependent on pliability of tissues: elastic fibers, smooth muscle, CT, etc

A

compliance

21
Q

During systole, arteries expand due to the presence of ?

A

elastic fibers

22
Q

__and continuous propulsion smoothen out the blood flow pulsations

A

elasticity

23
Q

absorption of pressure waves by the__ is dependent on the ___ of the vessel.

A

elasticity

compliance

24
Q

___ depends on the ratio of elastic to collagen fibers in the extracellular matrix

A

Compliance

25
Q

A relative increase in___ will limit expansion and reduce compliance

A

collagen

26
Q

Dampening of the pressure oscillations made by the heart is also called the ?

A

Windkessel effect

27
Q

explain the “second heart beat” during diastole

A

During diastole, contraction of aortic elastic fibers generate a pressure wave that propagates through the rest of the arteries.
– Elasticity absorbs the energy of the pressure wave (potential energy) and releases it during diastole (kinetic energy)

28
Q

Pulses are not completely flattened until they reach the?

A

small arteries and arterioles

29
Q

Decreasing the compliance of arteries has two effects:

A

Increases arterial systolic pressure

Decreases arterial diastolic pressure because there is less elastic recoil

30
Q

Elasticity normally absorbs and diminishes some of the pressure . A narrower, stiff, non-compliant artery has an ?

A

inherently greater resistance and generates a greater ΔP.

31
Q

low compliance generates a higher___ and a lower___ pressure

A

systolic

diastolic

32
Q

Increased SV increases PP and MAP by increasing the___ level.

A

systolic

33
Q

Decreased compliance increases PP by increasing___ and decreasing____ pressures. Decreased compliance indicated by increase of slope.

A

systolic
diastolic
C=ΔV/ΔP

34
Q

PP amplitude and wave form are indices of ?

A

vascular compliance.

35
Q

PP is a better index in ?

A

people over 60 (more atherosclerosis)

36
Q

Diastolic pressure is a better index for ?

A

younger people (more vascular resistance)

37
Q

Low compliance increases ___

A

PP amplitude

-Arteriosclerosis: low compliance leads to an increased PP (decreased diastolic pressure not always present)

38
Q

Low stroke volume decreases__?

A

PP amplitude
• Aortic stenosis: decreased SV leads to reduced PP
• Hypothyroidism: low heart contractility and low SV leads to a reduced PP

39
Q

explain Pulse waves

A

• It’s what you feel at an artery not caused by blood flow.
• Pulse wave travels 15 or more times more rapidly than blood flow
• A wave of distension travels to peripheral vessels, accelerating as it goes.
– Aorta: 3-6 m/s
– Large arteries: 7-10 m/s
– Small arteries: 15-35 m/s

40
Q

Increasing resistance along the arterial tree causes ?

A

the increased velocity

41
Q

Decreased compliance as one ages causes

A

an increase in pulse wave amplitude

42
Q

Arterial pulse waveform has 2 components:

A

• Forward (incident) traveling wave when the left ventricle contracts
• Reflected (rebound) wave returning from the periphery.
– In a compliant arterial tree, the reflected wave coincides with the diastole and augments perfusion of the coronary arteries.

43
Q

___ reflects off aortic and other vascular

bifurcations or regions of high resistance

A

Pulse wave

44
Q

__is the sum of the reflected wave and the forward wave, separated by a dicrotic notch

A

Waveform

45
Q

Decreased arterial compliance____ velocity of both

forward (incident) and reflected pulse waves

A

increases

– With age the reflected wave appears earlier and the dicrotic notch disappears

46
Q

Accelerated reflected wave has two actions:

A

– It is added to the forward wave to increase systolic
pressure amplitude (increase risk of stroke)
– It shifts to the earlier systolic phase such that there is less pressure during subsequent diastole for coronary artery perfusion.

47
Q

Decreased compliance is due to

A
  • Vasoconstriction / atherosclerosis

* Reduction in dilatory responses

48
Q

Vasodilation reduces the amplitude and velocity of the reflected wave, enhancing the dicrotic notch. This is due to?

A

– Nitric oxide (NO) vasodilation of artery; NO is released from endothelium in response to cardiac pulse pressure
– Decreased sympathetic activity

49
Q

Vasoconstriction increases speed of return of rebound wave & diminishes the dicrotic notch. This is due to:

A

– Decreased NO responsiveness to pulse pressure due to damaged blood vessels
– Increased sympathetic activity
– Atherosclerosis

Organ Systems (20 decks)

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