2.5.2 Hemodynamics Flashcards
How will left vagal stimulation differ from right?
But wait!!! The cross sectional area of a capillary is so so small…. How could this account for the blood flowing so slowly in the capillaries?
Because! The total cross-sectional area of all the capillaries in the system is much greater than all other systemic vessels.
Why is turbulent flow important when measuring blood pressure with a sphygmomanometer?
The flow you are hearing between the systolic pressures and diastolic pressures is a turbulent flow.
How will Isoproterenol if it primarily affects Beta 2 activation receptors affect MAP, and what will the baroreflex response be?
What is Runoff and what is something that can increase it?
Runoff is the rate at which blood leaves the arteries
Vasodilation can increase runoff
An increased HR will do what to preload?
Decreased preload
What will be the baroreflex response be to carotid massage?
What are two alternative ways to calculate vascular resistance?
How does venoconstriction result in increased venous return to the heart?
Venoconstriction decreases venous compliance, which causes pressure within veins to increase which increases pressure difference between peripherial veins and right atrium. The pressure gradient increases venous return to the heart.
D
Increased firing of what autonomic nerved would cause venoconstriction?
Increased firing of sympathetic nerves would cause venoconstriction. Which would stiffen the wall and decrease venous compliance, thus resulting in increased venous pressure.
What can be altered to affect the rate of runoff?
- Systemic arteriolar dilation (decreased TPR) results in a lower resistance to flow and a higher rate of runoff. This will result in lower arterial diastolic pressure.
- Systemic arteriolar constriction (increased TPR) results in a higher resistance and so a lower rate of runoff. This will increases arterial diastolic pressure.
How can gravity effect blood pressures?
Upon standing, the pressure in the veins below the heart increases while venous pressure decreases above the heart.
What systemic vessel has the lowest velocity of blood in them? Why might this be important?
Capillaries - The slow flow through capillaries facilitates solute exchange between blood and the surrounding tissue by increasing the time available for exchange.
C
What is Poiseuille’s Law and how does it relate to resistance in the body?
Poiseulle’s law describes flow through a tube. It states that resistance to flow in a tube is most determined by the radius of the tube.
How does ejection rate determine arterial systolic pressure?
The rate of ejection from the left ventricle determines how quickly blood volume in arterial system increases, which influences the peak systolic pressure attained.
In aortic stenosis, arterial pulse pressure is reduced because the rate of ejection of blood is decreased due to the high resistance of the aortic valve. Resulting in the pressure rising slower.
How does stroke volume affect arterial systolic pressure?
The rise in arterial pressure during ejection is directly proportional to the volume of blood added to the arterial system.
What systemic vessel accounts for the majority of TPR?
Arterioles
How will expiration be different in its effects on the left and right heart?
Since pressure in systemic veins is low and venous return is the same as arterial flow, what does this say for the resistance in veins?
It is very low
Because arterioles have the largest drop in systemic pressure, what can be said about their resistance?
The arterioles are the site of highest vascular resistance.
What is the formula for compliance of the arterial system?
What is the equation for MAP using systolic pressure and diastolic pressure?
MAP = Diastolic Pressure + 1/3 (Systolic Pressure - Diastolic Pressure)
MAP = Diastolic Pressure + 1/3 Pulse pressure
As a person ages, what happens to the Volume % increase vs pressure? (Hint the slope of the line is compliance)
The compliance decreases. This graph is delta V/ delta P which is the formula for compliance.
What is the effect of skeletal muscle pump on venous return?
The veins in the legs contain one way valves which direct blood to the heart. Contraction of skeletal muscles compresses veins in the leg, which forces blood toward the heart. When the skeletal muscles relax, the venous valves prevent backward flow of blood.
What is tubulent flow? How can it cause bruits?
Turbulent flow is a disruption of laminar flow. Turbulent flow causes vibrations of the blood vessel wall which are transmitted through the tissue and can be heard through the stethescope as bruits.
D
Calculate TPR assuming that MAP = 100mmHg, RAP = 0mmHg, and CO is 6 liters/minute.
How will nitroglycerine affect CO and TPR? What will the baroreflex response be?
Answer this!
The highest flow will be in tube C since it has the lowest resistance.
D
What would cause arterial pressure to rise?
This occurs when inflow is greater than outflow - during the rapid ejection phase of ventricular systole
What can happen to runoff time if heart rate in increased/decreased?
Decreasing heart rate increases runoff time, so arterial diastolic pressure will decrease.
Increasing heart rate decreases runoff time, so arterial diastolic pressure will increase
What accounts for the series and parallel resistance in the body?
Series - blood flow from aorta to arteriole to capillaries to veins account for the series
Parallel - the systemic organs
How does cross sectional area determine velocity?
The velocity of flow is inversely proportional to the cross-sectional area
What is the pathways by which venous pooling upon standing can occur? How will the affect CO?
Because veins are compliant, the increase in venous pressure upon standing will cause veins to distend - minimizing the increase in venous pressure. Venous return to the right heart will decrease upon standing, reducing EDV, decreasing stroke volume and thus reduce CO
How does arterial compliance affect arterial systolic pressure?
The aorta and large arteries stretch to some extent as blood is ejected from the left ventricle. This elasticity reduces the rise in arterial pressure during ejection.
Where is the major dropping point for pressure in the systemic vessels?
Arterioles - the drop decreases from 80-35mmHg
What will the baroreflex response be to carotid occlusion?
What are the two factors that determine arterial diastolic pressure?
- Rate of runoff - how fast blood flows from arterial to venous system
- Runoff time - runoff occurs during diastole (while ventricle is filling)
How will isoproterenol affect CO if it is selective for Beta 1 activation and what will the baroreflex response be?
What is the major determinant of runoff time?
Heart rate
What is the famous mnemonic for the effect of breathing on venous return to the heart?
How can expiration affect heart rate?
Decreased arterial compliance associated with aging can have what affect on systolic pressure?
With aging arterial compliance is reduced which results in a greater increase in arterial pressure during ejection compared to a younger person. As a result an older person will have higher arterial systolic pressure than that of a younger person during ejection of the same stroke volume.
The decreased arterial compliance will reduce elastic recoil during diastole, resulting in a faster decrease in arterial pressure during diastole and a lower arterial diastolic pressure than seen in a young person.
How can you determine central venous pressure?
Lay patient in a semi-supine position, and the distance in cm of the manubriosternal angle to the point of collapse of the external jugular vein is detemined. Then take this value and add 5 to determine the value.
What is the process that occurs after inspiration to account for the delayed closure of the pulmonic valve?
There is an increase in venous return to the right heart. Which will increase the ejection time. Leading to the splitting of the second heart sound.
B
What do each of the numbers designate?
1 - Systolic Pressure
2 - Diastolic Pressure
3 - Ejection
4 - Runoff
What is polycythemia?
This relates to people living at higher altitude. The response to having lower oxygen content is an increased production of red blood cells, resulting in increased blood viscosity and therefore greater resistance to blood flow.
How does blood viscosity relate to resistance to flow?
Blood viscoscity directly relates to resistance to blood flow.
A
Answer this!
Each tube will receive the same flow since resistance is the same, so each tube will receive 2 liters/minutes
What is the equation for venous return to the heart?
(Psystemic veins - Pright atrium) / Resistanceveins
How will adding resistance in series differ from resistance in parallel?
How does compliance compare between veins and arteries?
Arteries and arterioles have low compliance due to their thick musclar walls. A small increase in blood volume will increase their arterial pressure.
In contrast, venules and veins are highly compliant in relation. Large increases in venous blood volume creates a small increase in venous pressure.
How will inspiration affect the stroke volume in the left ventricle?
It will increase intrathoracic pressure leading to decreased pressure in pulmonary veins and decreased blood flow to left atrium and decreased LV EDV.
How will phenlyephine affect MAP and what will the baroreflex response be?
What would cause arterial pressure to fall?
When inflow is less than outflow (during diastole)
B
