Physio

Question 1

Main determinant of blood flow.

Answer 1

Tissue needs

supply/demand

Question 2

How are velocity and cross section area related?

Answer 2

Inversely

Question 3

Which blood vessels act as the control conduits that control blood flow?

Answer 3

Muscular Arteries

Question 4

Main determinant for systolic blood pressure.

Answer 4

Stroke Volume

Question 5

Main determinant for diastolic blood pressure.

Answer 5

Total Peripheral Resistance

Question 6

Major determinant for cardiac output.

Answer 6

Venous Return

Question 7

How is blood flow calculated?

Answer 7

F = change in pressure/resistance

Question 8

How is velocity calculated?

Answer 8

v=F/A

Question 9

How is pulmonary vascular resistance calculated?

Answer 9

PVR = (mean pulmonary artery pressure - left atrial pressure)/cardiac output

Question 10

What happens to resistance with turbulent blood flow?

Answer 10

Increase in resistance

Question 11

What does Reynold’s Number measure and what factors are involved?

Answer 11

Measures tendency of blood flow to become turbulent.

Re = (velocity of flow x diameter of vessel x density of blood)/viscosity of blood

Question 12

What the hell was he talking about with the energy gradient crap?

Answer 12

It basically is energy conservation. We know that velocity and cross sectional area are inversely related. So if a vessel narrows (decreasing area) the velocity increases.

When velocity increases, the kinetic energy of the blood increases. To compensate for the increase in kinetic energy, the only other factor (that we have to worry about), the pressure energy, has to decrease.

This maintains a conservation of energy in the system.

Question 13

If blood flow is dependent on a pressure gradient, how does it flow from a stenotic portion of a blood vessel with low pressure to a region of higher pressure distal to the stenosis?

Answer 13

Energy Gradient Crap.
-even though the pressure is higher distal to the stricture, the increase in kinetic energy provides the energy to flow from a section of low pressure to a section of high pressure.

Question 14

What are the variables in Poiseulle’s equation to calculate blood flow?

Answer 14

Flow = (pressure change x radius^4)/(viscosity x length)

Radius changes have the biggest effect on blood flow

Question 15

Biggest contributor to autoregulation.

Answer 15

Local mechanisms such as tissue needs

Question 16

How are compliance, volume and pressure related?

Answer 16

C = change in volume/change in pressure

Question 17

How does distensibility help to maintain blood pressure?

Answer 17

It accommodates extra blood volume in the vessels and ““buffers” the system to prevent much of a blood pressure increase.

Question 18

Describe the change in systolic and diastolic blood pressure in patients with Primary Systolic Hypertension due to atherosclerosis.

Answer 18

Systolic: increases
Diastolic: decreases

Atherosclerosis decreases the distensibility of the major elastic arteries (mainly the aorta). When blood is pumped into these vessels in systole the blood pressure rises to a high level.

Meanwhile, the muscular arteries further distal to the heart are dealing with increased blood flow due to the high pressure. They will distend (decrease resistance) the best that they can but once they reach their limit, they will send blood out through the capillaries and into the interstitial space to dissipate the pressure.

This loss of fluid in the vasculature leads to decreased heart filling and a lower diastolic blood pressure. Dumb.

Question 19

Where is central venous pressure measured?

Answer 19

In the right atrium where the IVC and SVC enter.

Question 20

What does inhalation and intubation do to pulmonary venous pressure upon inhalation.

Answer 20

Normal inhalation: an already negative pressure becomes more negative with inhalation. This expansion of the chest wall also decreases resistance in the pulmonary blood vessels leading to a drop in venous pressure.

Intubation: inhalation caused by positive pressure forcing air into the lungs causes an increase in pulmonary pressure. The decrease in resistance from the chest expanding does not account for the increased pressure from the air forced into the lungs.

Question 21

Cause of varicose veins.

Answer 21

Venous valve insufficiency.

Question 22

What happens to the blood vessels during anaphylaxis?

Answer 22

Capillaries normally only have blood flow when surrounding tissues require nutrients and waste removal. This prevents too much blood from entering the capillaries at one time. During anaphylaxis, the arterioles dilate all the sphincters regulating flow to the capillaries and blood fills them.

This results in severe hypotension and shock. It is treated with a vasoconstrictor like epinephrine.