3.6 Blood Pressure & Flow Flashcards
Which is longer: systole or diastole?
Diastole
Is aortic pressure higher during systole or diastole?
Systole
Is aortic pressure or ventricular pressure higher during diastole?
Aortic pressure. Decreases far less than ventricular pressure during diastole.
What two factors determine blood flow?
- Pressure gradient along a vessel
- Resistance to blood flow through a vessel
(think: what is pushing it forward? what is pushing it back?)
Which physics equation can be used to describe the flow of blood through a vessel? Which values are substituted for which others?
Ohm’s Law (V=IR)
Voltage becomes pressure
Current becomes flow
Resistance is still resistance
Therefore, the two main factors that influence blood pressure are flow and resistance to flow.
What is the name given to the value that represents the difference between systolic and diastolic blood pressure?
Pulse pressure
Why isn’t MAP simply the average of systolic and diastolic pressure?
Diastole lasts slightly longer. Therefore, more weight must be given to diastole.
How does a pressure gradient influence the direction of blood flow?
Blood will flow from areas of high pressure to areas of low pressure (kind of like osmosis)
What is one factor that influences total peripheral resistance (think: tunica media)
Vasoconstriction/Vasodilation
What is meant by resistance and conductance? What is their relationship, and why does this matter?
Resistance: Impediment to blood flow in a vessel
Conductance: Measure of blood flow for a given pressure difference
These two quantities are reciprocals of one another, meaning they are inversely proportional.
What is the relationship between conductance and diameter of a vessel?
Conductance is proportional to the fourth power of diameter.
Why do tissues need blood flow?
- Gas exchange (oxygen/CO2)
- Nutrient delivery
- H+ removal (pH conttrol)
- Hormone transport
- Thermoregulation
- Tissue ion balance
Does the body have the ability to send the ideal amount of blood to all tissues in the body all the time?
No. It has to be selective. This is why, for example, many regions of the body do not get very much blood flow during exercise.
Name three factors that influence vascular resistance
- Vessel Compliance
- Length and diameter of vessel
- Viscosity of blood
Why can’t you measure the flow of a capillary bed by measuring the flow of a single capillary?
At any given time, one capillary may be open, whilst the one next to it may be closed. This would not give a proper indication of the overall bed itself.
