Arterial circulation Flashcards
What is the Relationship between flow and pressure in tissues (vessels)?
Increasing pressure difference
-> The flow increases (follow Ohm’s law)
What is the difference between these 2 lines?
The slopes are difference
-> because they depend on the resistance (the left line has smaller resistance)
Is this graph applied to real life?
No
Make a schematic diagram (flow vs pressure) for lung type vessel and kidney type vessel
How to initiate the flow?
Increase pressure to achieve interstitial pressure
What is transneural pressure?
The difference between the pressure in vessel and pressure in the interstitial
We can observe ___ (linear/continuous) increase in flow with increase in pressure (exponential increase)
continuous
When the pressure increases a lot we will reach a point -> What will we find?
where we get a straight line
Make a graph (flow vs. pressure) in lung vessels
Why does the resistance related to the slope get smaller?
The resistance is not constant, and it depends on pressure
How can the lung vessels affect the resistances?
The wall is elastic
-> increasing pressure
-> increasing radius
-> decreasing resistance
How to calculate the resistance of the vessels? (based on hagens poissule law)
Resistance =
The pressure needed to generate a flow is called critical pressure
=> Why does it exist?
for example the RBCs being larger than capillaries so we need more pressure to squeeze them into the capillaries.
What is interstitial pressure?
a pressure outside the vessel
Lung type vessel
-> What type of increase does this graph show? Why?
it shows a logarithmic increase and that is because the resistance of the vessel is continuously changing.
Lung type vessel
-> Is this an active or a passive response of the vessels? Why?
This is a passive response of the vessels due to their elasticity.
Make a graph (flow vs. pressure) of kidney type vessels
Why does increasing pressure lead to increasing resistance? (in case of kidney type vessels)
Increasing pressure
-> increasing wall tension
-> induce a mechanical stimulus on mechanosensitive channels (on membranes of smooth muscle cells)
-> cause depolarization
-> activate voltage-gated calcium channels
-> make Ca2+ signal
-> cause vasoconstriction
-> decreasing radius
-> INCREASING RESISTANCE
In case of kidney type vessels
-> Is this an active or passive response?
This is an active response of the smooth muscles.
In case of kidney type vessels,
What happen to the graph if there is no more depolarization and there is a high pressure
Now after the slope being constant for a while there will be a linear increase in the flow with pressure.
In case of kidney type vessels,
How does the vessels act after reaching 150mmHg in pressure?
It acts as a rigid wall tube to show a linear relationship
In case of kidney type pressure,
In which range does the flow is constant?
Between 50mmHg and 150 mmHg
In case of kidney type vessels,
This regulation is called autoregulation
-> Why?
The vessels regulation itself
-> the flow becomes independent from pressure
According to The Hagen–Poiseuille Law, what can affect the resistance of blood (EXCEPT pressure)?
Viscosity of blood
What is the viscosity value of water?
1
What is the viscosity of blood plasma?
1.2
What is the normal hematocrit value?
50%
Make a graph to describe the viscosity of blood? (Relative viscosity vs relative hematocrit)
What happen to the viscosity if we increase hematocrit?
The resistance will increase
What happen to the viscosity if we increase hematocrit from 50% to 70%?
The viscosity will double
What happen if we have a high hematocrit (70%, for example)
Dehydration (does not have enough water)
-> Increase hematocrit
-> Increase pressure
-> very dangerous situation, especially in older people
Make a graph (viscosity vs. hematocrit) with glass viscometer and in biological samples
Make a graph to show the relationship between viscosity and diameter of blood vessels
Make a graph to show the relationship between hematocrit and diameter of blood vessels
What is the general diameter of arterioles
less than 300 µm
Why do we have lower pressure in arterioles comparing to other type of vessels?
Velocity of particles in center will be higher than velocities of other particles which are closer to the wall
-> Velocity of Red Blood cell is higher than blood plasma
why does the viscosity not increase as much in a biological sample like the glass tube viscometer?
This is because if we decrease the diameter of our blood vessels to a certain extent the viscosity will decrease and this happens in arterioles.
why does the viscosity decrease in arterioles?
This is because in this vessel type where diameter is below 300um viscosity acts differently as there will be a separation of the particles.
What is ferrous linguistic effect?
The RBCs are going to be located in the center and will have more velocity leading to particle separation will occur. This decreases the viscosity because of the speed separation.
What does the green line show?
The green line shows the change of the hydrostatic pressure in the circulatory system.
Why is the pressure the highest at the aorta?
The pressure is generated at the heart
The pressure is generated at the heart so this why it’s the highest at the aorta.
-> Why does it then show a continuous decrease?
the heart cannot provide continuous pressure but a pulsatile pressure.
After the capillaries we will have a ___ (linear/continuous) flow through the veins.
continuous
What is the main function of aorta (large artery)?
to convert this pulsatile intermittent flow into a continuous steady flow
What is the Windkessel effect?
helps to decrease the load on the heart and to minimize the systolic flow and maximize diastolic flow in the arterioles
The function of the aorta and large arteries is to convert this pulsatile intermittent flow into a continuous steady flow.
-> This is done by which effect?
the Windkessel effect
Make a schematic drawing of Windkessel effect with aorta
Pushing the water
-> Half goes to the container
-> Half goes out of the tube
What happen if we increase the pressure the volume of the aorta?
In the aorta it contains a lot of elastic tissue
-> this means when we increase the pressure
-> the volume of the aorta is increasing because of the elasticity which will increase the compliance.
In the cardiac cycle the pressure in the aorta due to ___
the contraction of the ventricles
In the cardiac cycle the pressure in the aorta due to the contraction of the ventricles and this pressure increase will increase the volume.
-> This extra volume will be stored in the form of ___
elastic energy.
Make a graph that describe the relationship between the volume of aorta and pressure
When the pressure stops increasing, what will the elastic energy of aorta be used for?
This elastic energy will be used to maintain the flow.
Describe pressure-volume relationships of aorta in different age groups
the pressure to volume relationship is supposed to be linear but in older people the elasticity decreases and the linear relationship will be modified and compliance will decrease.
What is arterial pressure?
the hydrostatic pressure in the largest vessel artery the aorta.
Draw the graph (pressure vs time) to demonstrate arterial pressure cycles
What is the systolic pressure?
80 mmHg
What is the diastolic pressure?
80 mmHg
What is pulse pressure?
= The difference between diastolic and systolic pressure
= 120 mmHg - 80 mmHg = 40 mmHg
What is the mean pressure?
= (1 x Ps + 2 x Pd)/3
What are the factors that affect the mean pressure?
Systolic and diastolic pressures
How to change the mean pressure?
by increasing the heart rate which will decrease the length of the diastole.
What are the 2 physiological determinants of arterial blood pressure?
- Cardiac output (corresponds to the stroke volume and heart rate -> can affect blood volume)
- Total peripheral resistance
(Mean arterial blood pressure
= Cardiac output (CO) x Total peripheral resistance (TPR))
What are the 2 physical determinants of the pulse pressure?
- Arterial compliance
- Change in the arterial volume
How can TPR affect the arterial blood pressure?
The other physiological factor which can determine the amount of blood that can leave the arterial system and continue through the circulatory system is the TPR. If the TPR increases then more blood will remain in the arterial system effecting the blood volume.
What happen if we increase the stroke volume?
more blood enters the arterial system so the blood volume will increase and the minimal volume will increase.
What happen When we increase the TPR?
more blood will remain in the arterial system increasing the blood volume but the difference between the volumes will stay the same
When we increase the TPR more blood will remain in the arterial system increasing the blood volume but the difference between the volumes will stay the same.
-> Why?
. This Is because the volume depends on the venous return.
-> the pressure difference will also stay the same but they will both increase
-> The mean pressure will also increase.
The TPR can be considered the main determinant of the ___ (which pressure?)
diastolic pressure.
Draw a graph to demonstrate how the stroke volume affect the arterial blood pressure
Draw a graph to demonstrate how the TPR can affect the arterial blood pressure
Draw a graph to demonstrate how the compliance affect the arterial blood pressure
How can compliance affect the arterial blood pressure?
decrease in compliance
-> the slope of the graph will change and the consequence is from the same volumes
-> there will be a lower diastolic pressure and a higher systolic pressure
-> the difference in pressure will be much higher.
-> The mean pressure will stay the same.
(This occurs in old people normally.)
What happen to the arterial pressure when you stand up?
the arterial pressure is fixed on the level of the heart because the arterial pressure is detected in the aorta.
-> This Is where we have a receptor that regulate the heart pressure and fix it on the same value.
What happen to stroke volume if we increase the blood volume?
Stroke volume will increase as well
What happen if there is an increase in blood viscosity?
TPR will increase
The effect of gravity on the blood pressure (give the important number)
1cm H2O -> 0.7 mmHg
