Factors determining the blood pressure: pressure on different parts of the circularity bed, measuring blood pressure Flashcards
Factors determining blood pressure Physiological effects:
Cardiac output:
Increase of heart rate:
Total peripheral resistance (TPR):
Factors determining blood pressure
Physical effects:
Arterial blood volume:
Arterial distensibility and compliance:
What is runoff
The amount of blood that is forwarded from the atrial side of the circulation into the venous part during systole of the heart.
Factors determining blood pressure Physiological effects:
- Cardiac output:
If the C.O. is suddenly increased experimentally the
mean arterial pressure increases to a value that is able to forward the increased volume of blood appearing in the arterial system.
o After some cardiac cycles the increased C.O. increases the blood pressure, which then forwards the increased amount of blood to the venous side.
Factors determining blood pressure Physiological effects:
Increase of heart rate:
Increases the blood pressure because blood is
forwarded from the venous reservoir system into the arterial resistance system.
Factors determining blood pressure Physiological effects:
Total peripheral resistance (TPR):
The arterial blood volume grows and a consequent increase of the mean arterial pressure helps to
forward the stroke volume towards the increased resistance.
Factors determining blood pressure:
Physical effects:
Arterial blood volume
Va changes at each cardiac cycle as a result of the difference between stroke volume and runoff.
Under constant compliance and peripheral resistance the increase of the Va causes the increase
of both the pulse pressure and the mean arterial pressure.
Factors determining blood pressure:
Physical effects:
Arterial distensibility and compliance:
Vessels are capable to take up more blood when the pressure increases because their wall is distensible.
What is Distensibility
= the capacity to expand/stretch under pressure
Definition of distensibility
Def: The volume change related to the unit change of pressure and to the original volume.
Equation of distensibility
▪ D = ∆V/∆P x Va
Definition of Compliance
Def: If the original volume of the system is ignored, and only the relative volume change per unit pressure change is observed
Equation of compliance
▪ C = ∆V/∆P
When is distensibility used
Distensibility is
used when one compares circulations
When is compliance used
Compliance is used when the absolute change is of interest.
