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Physiology > Factors determining the blood pressure; pressures on different parts on the circulatory bed, measuring the blood pressure > Flashcards

Factors determining the blood pressure; pressures on different parts on the circulatory bed, measuring the blood pressure Flashcards

1
Q

What are the energetic components maintaining pressure gradient?

A
  • Potential energy
  • Kinetic energy
  • Flow friction
  • Restistance
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2
Q

What is potential energy?

A

Pressure exerted onto the wall of the container (in this case: the vessels)

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3
Q

What is Kinetic energy?

A

The work needed to a body of a given mass from rest to its stated velocity

1/2m x v^2

m= mass, v= velocity

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4
Q

What is flow friction?

A

It creates energy loss, so the total energy is less at the outlet than at the inlet of the tube.

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5
Q

What is the resistance?

A

The resistance is determined by flow rate, in other words:

the geometry of the tube and the properties of the fluid (viscosity)

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6
Q

What is the Pilot system?

A

Total energy - Potential energy = Kinetic energy

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7
Q

How can you measure the potential energy in the Pilot system?

A

If the opening of the probe is perpendicular to the direction of the flow, then the height of the fluid indicates the measure of the potential energy of the system at the insertion point.

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8
Q

How can you measure the total energy in the Pilot system?

A

If the opening is parallel to the direction of flow, the height of the fluid in the probe gives the total energy of the system at the insertion point.

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9
Q

How can you measure the Kinetic component of the Pilot system?

A

The difference of the fluid levels in these two probes is the measure of the kinetic component of the system.

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10
Q

What happens during Narrowing of the blood vessles?

A

Under standard flow conditions narrowing causes an increase of kinetic, and decrease of potential component.

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11
Q

What is Fahraeus-Lindquist effect?

A

Fahraeus-Lindquist effect makes red cells flow much faster through small arteries.

e.g:
vessels of about 200um diameter has higher viscosity than in the very small vessels, and the viscosity will drop dramatically (Fahraeus-Lindquist effect)

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12
Q

What is the viscosity of the blood?

A

It is a function of its hematocrit.

  • At around normal hematocrit values the relative viscosity of the blood is 3.5
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13
Q

What can happens during hemoconcentration?

A
  • an increase in the hematocrit value to 50 rauses the viscosity to 7.0!
  • Hemoconcentration is burdening the heart. So it has to work at much higher level to maintain constant pressure (and perfusion) under such circumstances.
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14
Q

In what parts of the circulation can you measure blood pressure?

A
  1. Arterial blood pressure
  2. Pressure in the capillary system (microcirculation)
  3. Venous blood pressure
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15
Q

What are the factors maintaining the blood pressure in Arteries?

A
  1. Work of the heart
  2. Total peripheral resistance (TPR)
  3. Role of the structure of the vessels
    - arterial distensibility and compliance
  4. Distribution of blood in the circulatory system
    - Volume of blood in the arterial sytem.
  5. Location of the organs in the circulation
    - Paralelly attached organs in the circulation
  6. Types of blood flow.
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16
Q

Which factors maintains a close to constant peripheral blood pressure in the Arterial blood pressure?

A

The work of the heart, the peripheral resistance of the vessels, the arterial blood volume together with the distensibility of the vessel system.

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17
Q

What ensures the constant blood perfusion (volume flow) in the tissues?

A

The work of the heart, the peripheral resistance of the vessels, the arterial blood volume together with the distensibility of the vessel system maintaines a close to constant peripheral blood pressure -> AND THIS ensures, in a serially and paralelly attached system of vessels, a close to constant blood perfusion in the tissues!

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18
Q

What makes the major form of nutrient and metabolite exchange?

A

At the level of microcirculation (capillary system) the perfusion causes appropriate diffusion of materials, such as the major form of nutrient and metabolite exchange

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19
Q

What determines the volume of ISF (iterstitial fluid?

A

The hydrostatic and oncotic forces (Starlings forces) result in either filtration or resorption, determining the volume if ISF

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20
Q

What are the main parameters describing the Work of the heart?
(arterial blood pressure)

A
  • Cardiac Output (CO)
  • Runoff (Qr)
  • Increased Frequency
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21
Q

What is Cardiac Output?

A

The amount of blood forwarded into the aorta from the left ventricle per unit time
(arterial blood pressure)

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22
Q

What is the Runoff?

A

It is the amount of blood, which moves from the arterial to the venous part
(arterial blood pressure)

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23
Q

How is the Runoff during Systole?

A

The Runoff during Systole is lower than SV, since the arterial part stores a fraction of the SV (arteries enlarging), that fraction is forwarded to the venous part during Diastole.

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24
Q

How is the Runoff during regular and continuous activity?

A

The value of Runoff is equivalent with the CO, while its actual value influences the Blood pressure.

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25
Q

What happens if the Runoff decreases?

A
  • Less blood is forwarded to the venous part
  • then the blood pressure increases, “extrusion” of the blood in the arterial side; and it can only be corrected by the extra work of the heart.
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26
Q

What is the Increased Frequency of the Arterial blood pressure?

A
  • It also increases blood pressure, since increased blood volume is forwarded from venous reservoir to the arterial resistance system.
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27
Q

Why does the increased arterial volume (Va) create increased blood pressure?

A

Becuase the runoff can not match up to the increased SV immediately.

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28
Q

What types of Increased Frequency exists?

A
  1. Artificial Increase
    - Pacemakers
    - only diastolic duration is decreased
    - CO decreased
  2. Natural increase
    - Sympathetic activation
    - reduced systolic time
    - proportionally reduced diastolic time
    - CO increases
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29
Q

What is the Total peripheral resistance (TPR)?

arterial blood pressure

A
  • The increased peripheral resistance (arterial contraction) will also increase the arterial blood pressure
  • To keep the elevated blood pressure, the heart needs extra work (elevated performance)
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30
Q

What happens when there is a sudden increase of TPR?

A

it will decrease the Runoff (Qr) because the increased resistance does not allow to press through the same amount of blood to the venous side - > therefore a temporary increase in arterial volume (Va) occurs. This increases the average arterial pressure to the level which is able to forward the extra volume through the increased TPR.

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31
Q

What is the Role of the structure of the vessels?

A

Vessels are not rigid tubes, but distensible ones due to:

  • Elastic elements
  • Myogenic elements

These two factors keep the vessels in contracted state in resting.

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32
Q

What happens in the Role of the structure of the vessels if there is an Increased pressure?

A

It creates a non-linear, but sudden increase of flow due to the increasing diameter of the distensible wall.

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33
Q

What happens in the Role of the structure of the vessels if the pressure drops?

A

It causes a inproportional decrease in vessel diameter, due to the intrinsic-myogenic and vasoconstrictor tone.

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34
Q

What is Critical Closing Pressure?

A

The pressure where the vessels are collapsing, due to vasoconstrictor tone.

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35
Q

What is Arterial Distensibility?

A
  • Distensibility is the volume change related to the unit change of pressure and related to the original volume.
  • Vessels are able to take up more blood when the pressure increases, becuase their wall is
    D = dV / dP x Va

(arterial blood pressure, structure of the vessel)

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36
Q

What is Compliance?

A

When the original volume is not taken into consideration
= the volume change per unit pressure change

C= dV / dP

(arterial BP, structure of the vessel)

37
Q

When is Distensibility used?

A

If different circulations are compared

38
Q

When is Compliance used?

A

When the absolute change is of interest

39
Q

When are the vessels able to take up more blood?

A

When the pressure increases, becuase their wall is
D= dV / dP x Va

(arterial distensibility)

40
Q

Definition of the Laplace´s Law?

A

To maintain the same blood pressure (P) in a larger vessel requires increased wall tension (T), which requires more O2

41
Q

What determines the Distribution of blood in the circulatory system?

A

By the total cross sectional area of vessels and the structure of the wall

42
Q

What is the largest cross sectional section?

A

It is the capillary bed (600-100x > aorta), apart from that the majority of the circulating blood volume still resides in the veins, due to its extreme distensibility.

43
Q

What is the physiological relevance of Distribution of blood in the cirulatory system?

A

Cardio-vascular regulation may “rearrange” the blood distribution according to the need of the organism (redistribution)

44
Q

What is the effect of arterial volume on blood pressure?

(distribution of blood in the circulatory system?

A

The increase of SV (the increase of arterial volume change) will cause sudden increase of average arterial pressure and pulse pressure.

this is characteristic to the healthy animal, where the compliance is constant.

45
Q

What are the Parallely attached elements in circulation?

A

The circuatory bed of the individual organs are parallely attached to each other.

46
Q

What makes the Parallely attached elements in the circulation possible?

A
  • That the change in the perfusion of one organ does not suddenly changes the work of the heart.
  • since the sum of the resistance of parallely attached elements is smaller than the resistance of the individual organs of the system.
47
Q

What is the advantage of that the Circulation of the individual organs are parallely attached to each other?

A

The relative blood supply of individual organs may change withoug a substantial increase of heart work, since the sum of resistance of the parallely coupled elements is smaller than the resistance of the individual elements.

48
Q

The heart should work against the resistance of?

A

Serially coupled arteries, capillaries and veins.

49
Q

What is serially coupled elements?

A

Arteries, capillaries, veins

50
Q

The circulatory bed of the individual organs are parallely coupled to?

A

Both the systemic and the lung circulation

51
Q

Perfusion (volume flow) is determined by?

A

The Ohm´s law.

  • where the crucial factors are the pressure differences between the two end points (delta P; pressure gradient) and the resistance of the System (R).

Q(ml/min) = deltaP / R

52
Q

What is the Ohm´s law?

A
  • where the crucial factors are the pressure differences between the two end points (delta P; pressure gradient) and the resistance of the System (R).

Q(ml/min) = deltaP / R

53
Q

Types of flow in the arterial blood pressure:

A
  • Laminar

- Turbulent

54
Q

Reynolds number (Re) is important in?

A

Laminar and Turbulent flow.

v x D / u
v= velocity of blood flow
D= diameter of blood vessels
u= kinetic viscosity

Re < 2320 = LAMINAR blood flow

Re > 2320 TURBULENT blood flow

55
Q

What is margination?

A
  • In normal blood flow erythrocytes are confined to a central axial column, displcing leukocytes towards the wall of the vessels
  • As blood flow slows in inflammation more White blood cells assumes peripheral position along the endothelial surface.
    THIS process of leukocyte accumulation is called MARGINATION.
56
Q

What maintaines the leukocytes against the venular wall?

A

The Laminar blood flow

57
Q

Define Laminar blood flow:

A

No turbulence, sheets of fluid move above and next to each other without vortex formation

  • it also maintaines the leukocytes against the venular wall
58
Q

Define Turbulent blood flow:

A

Due to high velocity of the flow turbulence occurs, which can be characterized by the Reynold+s number (NR)
If NR > 3000 - the flow is turbulent

59
Q

What are the physiological relevance of laminar flow?

A
  • resistance is smaller, so less work of the heart (Stokes-law).
  • Exchange of material is facilitated next to the wall (due to the slow flow rate next to the wall)
  • Blood cells are arranged in the axis of the flow, so the resistance drops substantially.
60
Q

Factors maintaining the Capillary blood pressure

A

Microcirculation

61
Q

Factors maintaining Venous blood pressure:

A
  • “vis a tergo” the work of the heart (force from behind)
  • Gravitation
  • Venous valves
  • Skeletal muscle pump
  • Changing pressure in chest and in abdomen
  • CVP (central venous pressure)
62
Q

What is the Skeletal muscle pump?

A

Rythmic changes of muscle tension “pump” the blood, direction of flow is always centripetal due to the valves
- in case of weak muscle tension, blood accumulates in the vein, creating regrogram capillary flow - increased pressure -> leading to odema.

63
Q

What is the “Chest pump”

A

During inspiration intrathoracal pressure decreases and facilitates the filling of right atrium (RA),

while abdominal pressure changes the trasnural pressure of veins running through the abdomen.

64
Q

Blood flow is maintained by?

A

Blood pressure (beyond the work of the heart)

65
Q

Blood pressure is maintained by?

A

The work of the heart and the Peripheral Resistance.

66
Q

The peripheral blood pressure is kept in?

A

a narrow range by the cardiovascular regulatory mechanism. That guarantees the migration and transport of substances in the territory of microcirculation.

67
Q

Where is the blood pressure highest?

A

In the systole.

68
Q

What is the mean arterial pressure?

A

is the weighted average of the systolic and diastolic pressure

69
Q

Blood pressure at the different part of the circulation:

A
  • Arterial blood pressure
  • Capillary blood pressure
  • Venous blood pressure
  • Static pressure
  • Due to gravity
70
Q

Blood pressure at different part of the Arterial blood pressure:

A
  • Systolic
  • Diastolic
  • Pulse pressure
  • Mean arterial pressure
71
Q

What is Systolic pressure?

A

Blood pressure measured in the arterial system at the end of systole (heart contraction; human ca 120 mmHg)

72
Q

What is Diastolic pressure?

A

Blood pressure measured in the arterial system at the end of diastole (heart relaxation; human ca 80mmHg)

73
Q

What is pulse pressure?

A
  • Difference between systolic and diastolic pressures
  • 120-80 = 40mmHg
  • Influenced by stroke volume and arterial compliance
74
Q

What is Mean arterial pressure?

A
  • during normal cardiac cycle, diastole is longer than systole (c 2 timer).
  • mean arterial pressure is the weighted average of the systolic and diastolic pressure (due to difference in duration)

(Psyst + 2 x Pdiast) / 3

75
Q

What is static pressure?

A

Blood pressure measured post mortem
- arterial blood pressure never drops to 0 in the circulation due to the static hydrostatic pressure in the vessels, ca 7mmHg

76
Q

Relationship between blood pressure and body size:

due to gravity

A
  • there is no direct correlation between the size of an animal and the arteria blood pressure, however mammals with large vertical distance between the heart and the brain exhibit the highest pressure.
77
Q

Measurement of blood pressure can be done by?

A
  1. Direct method
  2. Indirect method
    - Palpation
    - Ausculation
78
Q

What is the Direct method of blood pressure measurement?

A

1770: A glass catheter inserted to the carotid and height of the fluid column is measured.

Today: inserting a fluid-filled catheter into the carotis, which is connected to a pressure transducter taht converts the oscillation of the arterial pressure into recordable electrical signals.

79
Q

What is the Palpation method of Indirect blood pressure measurement?

A

Brachial artery first compressed then released slowly

  • If we raise the cuff pressure over the systolic pressure, circulation will cease in the compressed brachial artery.
  • then, if the pressure in the cuff is decreased slightly below the systolic pressure, at the peak of the systole a small volume of blood will slip through between the walls of the artery before they clap together again.
  • at this point pulse o the radial artery may be felt again (= systolic blood pressure)
  • diastolic blood pressure can not be determined by this method
80
Q

What is the Ausculatation method of measuring indirect blood pressure?

A
  • A clear tapping sound is heart at every pulse beat

- the appearance of this sund indicates the value of systolic blood pressure.

81
Q

What is the pressure pulse?

A
  • The “pulse” is produced by a pressure wave in the arterial system as a result of the contraction of the left ventricle.
  • this wave may be felt in most major arteries altough the most commonly used vessels are the radial and carotid arteries.
  • the aortic pressure wave is creating a deflection of arterial wall, which is propagaed in the arteries with high speed.
82
Q

What is the Dicrotic Notch og the Pressure pulse?

A
  • It is the effect of reflected pressure wave

- Reflection wave gets higher getting farter away from aorta.

83
Q

What is the Incisura of the Pressure pulse?

A
  • On the descending part of the aortic pressure wave a small notch appears during diastole (closure of semilunars)
  • it dissapears from the pressure curve moving away from the aorta, while on the pulse wave a dicrotic notch will appear farer to the aorta, e.g. on the femoralis.
  • Due to the reflected pressure the systolic pressure is higher in the a.femoralis than in the aorta, but mean arterial pressure is always higher centrally.
84
Q

How is a Flow pulse generated?

A

The flow rate (speed) is changing according to the varying pressure circumstances during systole and diastole - therefore a flow pulse is generated.

85
Q

The flow rate in aorta is?

A

Systolic 40cm/sec

86
Q

The flow rate in the capillaries is?

A

0.33 mm/sec. Drops tremendously!

87
Q

Where can Flow pulse be seen?

A

From aorta till arterioles, and disappears at metarterioles

88
Q

Pulse diagnosis can be carried out with?

A

Sphygmograph

89
Q

Factors describing the pulse:

A
  • Frequency (frequens, rarus)
  • Rhythm (regular, irregular)
  • Amplitude (magnus, parvus)
  • Steepness (celer: quickly increasing. Tardus: slowly increasing)
  • Tensions (durus: hard, mollis: soft)

Physiology (11 decks)

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