Lecture 14: Special Circulations

Question 1

What are the three ways that blood flow can be autoregulated?

Answer 1

1) Myogenic tone: automatically constricts in response to stretch
2) Metabolites: cause vasodilation usually
3) Autonomic nervous control (baroreflex)

Question 2

Describe Fick’s principle and its significance

Answer 2

O2 consumption = Q*(PO2 difference between arteries and veins). In the coronary vessels, there is near maximal extraction of O2, so during exercise, to increase O2 consumption, can’t just extract more O2 from the blood like in the rest of the body. therefore, flow must be increased

Question 3

Describe the path of coronary circulation

Answer 3

right coronary artery feeds RV, SAN, AVN
left coronary artery branches into left anterior descending artery and circumflex artery. Feeds LV, Bundle of His.
Feeds into coronary sinus

Question 4

How can coronary blood flow be regulated?

Answer 4

Mechanical: ventricular compression. Temporary ischemia each time systole occurs. Since the RV wall is less thick, there is less compression and less ischemia in those arteries
Neural: NA binds to alpha1 receptor, Gq, PLC, vasoconstriction
Metabolic
Myogenic

Question 5

Describe coronary artery disease and how the body fights it

Answer 5

This is slow-onset ischemia. However, anastamoses form and cause collateral blood supplies to go around the blockage. This angiogenesis is due to increase in VEGF and HIF

Question 6

Describe skeletal muscle circulation and cerebral blood flow

Answer 6

sympathetic tone predominates
during exercise, metabolic effects predominate
has reactive ischemia (metabolite induced vasodilation)

cerebral: uses glucose as fuel, neural control very little. Goes through circle of willis. patients much more sensitive to CO2, can’t control blood pressure as well (less autoregulation)

Question 7

Describe blood flow in apical and non-apical skin

Answer 7

Apical: has anastamoses, glomus bodies between arteries and veins (bypass) that are controlled by sympathetic tone. Very low resistance, so there is high blood flow, allows for heat dissipation

Non-apical: neural control more important thatn metabolic regulation. cholinergic receptors on sweat glands cause increased sweat, increased release of bradykinin. This causes vasodilation.