Coronary and Pulmonary Circulation

Question 1

extravascular pressure is greater in which- epicardial coronary or subendocardial arterial plexus?

Answer 1

subendocardial plexus= more sensitive to damage

-even greater on L side

Question 2

Ohms law and coronary blood flow:

Answer 2

Change in pressure (Inlet-outlet)/Resistance

SAME FOR pulmonary flow

Question 3

Resistance is whose law? What is the main factor we consider?

Answer 3

Poiseuilles law

inversely related to radium^4
(also length and viscosity of fluid)

SAME FOR pulmonary flow

Question 4

Regulators of coronary vascular tone:

Answer 4

1) Systolic compression
2) Myogenic mechanisms
3) Metabolic factors
4) autonomic control

Question 5

When is coronary flow lowest?

Answer 5

End of diastole - end of isovolumetric contraction = A LOT OF TENSION IN THE VENTRICLE!

Question 6

When is coronary flow intermediate level?

Answer 6

throughout most of systole

Question 7

LV is maximally perfused during:

Answer 7

diastole!

Question 8

LV is minimally perfused during:

Answer 8

systole with lowest point at the end of isovolumetric contraction

Question 9

How to supply the heart with more O2?

Answer 9

Must inc blood flow - the heart already pulls almost all the O2 out of the blood it gets so that is not an option - must inc flow (dilate vessels!)

Question 10

Mechanisms to inc O2 demand for heart:

Answer 10

O2 supply:

• inc coronary conductance (opposite of resistance) –> vasodiilation
• inc diastolic perfusion pressure
• inc arterial O2 concentration - long term= more Hb

Question 11

O2 demand increases when?

Answer 11

Inc HR

• inc contractility
• inc wall tension

Question 12

What is myogenic regulation:

Answer 12

its autoregulation that no matter the pressure (range of pressures) blood flow is actively maintained at constant level

Question 13

What is coronary reserve:

Answer 13

the difference between passive movement (capacity of pipes) due to pressure and the autoreg curve (active maintenance of tension in vessel)

Question 14

Example of when coronary reserve is reduced?

Answer 14

-disease can impair dilatory potential of vessels (plaque, atherosclerosis?) –> reduced blood flow fora given perfusion pressure

Question 15

Metabolic regulation of coronary blood flow is measured/stimulated how in the heart??

Answer 15

non-pathological hypoxia ==> tells the system to crank out some ATP + adenosine byproducts (adenosine also vasodilate the vessels)

Question 16

Sympathetics regulatino of blood flow:

Answer 16

PHASE 1
-stimulation causes transient vasoconstriction via direct action of NE on alpha receptors

PHASE 2
-then vasodilation - indirect effect bc METABOLIC regulation stimulated = hypoxia –> ATP –> adenosine vasodilation stuff

Question 17

Special features of pulmonary vessels?What does this do for us?

Answer 17

• high elastic content
• low smooth muscle content

allows for phasic distention to accomodate entire CO each cycle
–>opposite of autoreg (pressure changes with respect to change in flow)

(LOW PRESSURE< LOW RESISTANCE< VASCULAR DIFFERENCES compared to systemic circulation)

Question 18

Blood flow through Zone 1 Lungs:

Answer 18

-low capillary hydrostatic pressure because we are going up hill

Question 19

Blood flow through Zone 3 Lungs:

Answer 19

-High capillary hydrostatis pressure

Question 20

Why do crackles occur in Zone 3 first?

Answer 20

inc capillary hydrostatic pressure compared to other zones bc it is easy for blood to follow gravity to the bottom of lung = lymph drainage of excess fluid = crackles

Question 21

Ventialation is highest?

Answer 21

at the apex

Question 22

Perfusion is highest?

Answer 22

at the base

Question 23

V/Q at the apex is? at the base?

Answer 23

apex: large number
base: small number

Question 24

Passive mechanisms for regulation of pulmonary blood flow:

Answer 24

1) recruitment - adding more pipes - opening previously closed capillaries
2) distention - making the pipes bigger - accomodation of inc blood volume

Question 25

Active mechanisms for regulation of pulmonary blood flow:

Answer 25

1) hypoxic vasoconstriction
- caused by airway obstruction, high altitude, acute lung damage, COPD
- close area off by constricting adjacent blood vessels to divert blood to better areas
- “Decrease wasted ventilation”
2) other metabolites (limited in normal function)

Question 26

What happens with long term hypoxic vasoconstriction:

Answer 26

hypoxic stimulus for a while will cause hypertrophy of the smooth muscle in vessels = even more resistance to flow = inc pulmonary pressure = RV hypertorphy = RV dilation, valvular issues and evenually failure