1.4 Control and Regulation of the Coronary Circulation Flashcards
Where is the decrease in coronary circulation during systole noticed most/least? Why?
Most: Endocardium
Least: Epicardium
Perhaps flow remains most constant in larger epicardial arteries, but is more obstructed in deeper, endocardial arteries
Where is the decrease in coronary circulation during systole noticed most/least? Why?
Most: Endocardium
Least: Epicardium
Greater relative change in compression between subendocardium and subepicardium during systole than diastole
What is perfusion pressure?
The pressure gradient that causes blood flow
What metabolic factors are released by the mycocardium during increased metabolic demand?
- PCO2 inc, PO2 dec (respiration)
- H+ inc (some anaerobic capacity), K+ inc
- Adenosine Inc (ATP hydrolysis)
Describe the observation of “redundancy” when coronary blood flow autregulation pathways are isolated
Other pathways compensate; there are a wide range of influences working to regulate coronary blood flow
Describe the distribution of alpha/beta receptors along the coronary vasculature
Larger, upstream: alpha (vasoconstrict)
Smaller, intramuscular: beta (vasodilate)
Is the effect of NO released by endothelial cells constant despite perfusion pressure?
No; it is greater in times of reduced perfusion pressure (you can do the maths to prove it)
What type of force can prompt endothelial cells to produce NO
Shear stress; can be others as well
What are the fundamental determinants of coronary blood flow?
- Coronary perfusion pressure
- Coronary vasomotor tone
What factors influence vasomotor tone?
- Extravascular influences
- Endothelial factors
- Metabolic factors
- Neuro-humoral factors
- Endocrine and paracrine factors
What factors influence vasomotor tone?
- Extravascular influences
- Endothelial factors
- Metabolic factors
- Neuro-humoral factors
- Endocrine and paracrine factors
Describe the regulation of coronary blood flow during physiological stress
- Under normal conditions, parallel mechanisms act to increase CBF
- If one such mechanism is inhibited, other compensatory vasodilator mechanisms appear to provide cover
