Lecture 10- Controlling the heart and blood pressure Flashcards
What does the left ventricle generate pressure for? What does this mean?
The systemic circulation, therefore need a powerful beat as blood has to get out to the far reaches of the body.
What is MAP and what is it critically important for maintaining?
- Mean arterial blood pressure
- Important determinant of blood flow
- Is the P in the haemodynamics equation.. Q = DP/R
What is the blood pressure like in the major arteries?
- High
- Oscillatory due to pulse pressure (cycles of high and low correspond to beats of the heart)
What happens to blood pressure as we go down the supply chain?
- Blood pressure falls steeply across the arterioles, capillaries, and venules
- Oscillatory nature is reduced (pulse pressure disappears)
In general what is the blood pressure in veins like?
-Blood pressure is very low in veins.
What does the difference in blood pressure in the supply (arteries) side and drainage (veins) side cause?
-Creates a driving force for blood flow
What is arterial blood pressure and volume determined by?
-Balance between blood flows “in” and “out”
What does blood flow into the arteries cause?
- Fills arteries
- Increases arterial blood volume
- Raises arterial pressure.
What does blood flow out of the arteries cause?
- Drains arteries
- Decreases arterial blood volume
- Lowers arterial pressure.
Why does the pressure in arteries fluctuate so much depending on the volume of blood passing through?
Walls are rigid so can not expand and dilate like that of veins
What is blood flow into the arteries called?
- Cardiac output
- Measured in relation to time
What is blood flow out the arteries determined by?
- Arterial Resistance
- Can either hold up the blood or make it easier for it to leave
Arterial pressure =
Cardiac output x Total Peripheral Resistance
MAP = CO x TPR
What equation is the arterial pressure equation just a rearrangement of?
P = Q x R
rearranges to… Q=P/R
What is cardiac output determined by?
Stroke volume x Heart rate
What combinations of factors will result in increased arterial volume and Pressure?
- Increase cardiac output (increase inflow)
- Increase resistance (decrease outflow)
Basically more blood= higher pressure
What is meant by the term stroke volume? What unit is it measured in?
- Contraction strength i.e. the volume of blood pushed out with every beat
- L/beat
What is meant by the term heart rate? What unit is it measured in?
- Contraction speed
- beats/min
What is the unit for cardiac output?
L/min
In the ‘ putting it all together’ diagram what is the SV?
The difference in ventricular volume before and after ejection
What is the approach for a mouse to meet cardiac output?
- Stroke volume every small but heart rate is very fast to compensate
- Means that oxygenated blood can reach far parts of the body (just as we need)
What is the approach for a whale to meet cardiac output?
-Stroke volume very large (has huge, powerful heart)
so heart rate can be a lot slower and still meet demands
In a healthy human heart how do we meet demands for cardiac output?
- Method quite balanced
- Both stroke volume and heart rate are moderate
What do we see in failing human hearts in terms of maintaining cardiac output?
- Stroke volume is reduced as heart is not as efficient at pumping everything out
- As a result heart rate goes up to compensate
- The results in further damage as the heart is having to work so much harder to maintain mean arterial blood pressure