This document discusses the physiology of coronary blood flow. It begins with an introduction and overview of topics to be covered, including the anatomy of the heart, coronary blood flow, control of coronary blood flow, and nervous control. It then provides details on the coronary arteries and veins, factors that influence coronary blood flow like oxygen demand and determinants of oxygen consumption, and mechanisms that control blood flow like metabolic regulation and reactive hyperemia. It concludes with a discussion of how autonomic nervous stimulation can affect coronary flow both directly through effects on blood vessels and indirectly by altering cardiac work and oxygen demand.

1. PRESENTED BY:
Dr. Hrudi Sundar Sahoo

2.  INTRODUCTION
 PHYSIOLOGIC ANATOMY OF HEART
 CORONARY BLOOD FLOW
 CONTROL OF CORONARY BLOOD FLOW
 NERVOUS CONTROL
 CONCLUSION

3.  The word hemo -dynamics – means blood circulation in
the human body.
 Cardiovascular hemo -dynamics comprises of blood
circulation to the heart and in turn the blood circulation
regulated by the heart.

4.  Main coronary arteries lie on the surface of the heart
and small arteries penetrate into the cardiac muscle
mass.
 Heart receives nutrition supply through these arteries.
 Left coronary artery supplies mainly anterior and
lateral portion of left ventricle.
 Right coronary artery supplies most of right ventricle as
well as posterior part of left ventricle.

5.  Venous blood flow from left ventricle leaves by way of
coronary sinus.
 Most of venous blood from right ventricle flows
through small anterior cardiac vein directly into the
right atrium and not connected with coronary sinus.
 Small amount of coronary blood flows back into the
heart through Thebesian vein.

6.  Resting coronary blood flow in human, average is
approximately 225ml/minute, Which is 0.7 to 0.8 ml
per gram of heart muscle.
 During diastole cardiac muscle relaxes completely and
no longer obstruct the blood flow through the left
ventricular capillaries.
 This is phasic changes in coronary blood flow during
cardiac muscle compression.

7.  During cardiac contraction – Intra myocardial pressure
in the inner layer of the heart muscle is so much greater
than the outer layer
 It compresses the sub endocardial blood vessels far
more than it compresses the outer vessel.

8. I. Oxygen demand major factor in local blood flow
regulation.
II. Determinants of oxygen consumption.
III. Importance of increase in coronary blood flow in response
to myocardial oxygen usage.
IV. Reactive hyperemia in coronary system.

9.  Local metabolism as the primary control of coronary
flow .
 Blood flow through coronary system is regulated
almost entirely by vascular response to the local
needs.

11.  Blood flow in coronary arteries is proportion to the
need of cardiac musculature for oxygen.
 Decrease in oxygen concentration in the heart causes
vasodilator substance to be released from the muscle
cells .

12.  There are different factors that can alter myocardial
oxygen consumption.
 Cardiac oxygen consumption related to work
performed by the heart.
 Greater the work greater the oxygen consumption.

13.  Important principle of heart function is that myocardial
energy consumption and oxygen usage are very nearly
proportional to tension time.
 The time that the tension is maintained during cardiac
cycle .

14.  Consumption or stimulation of heart by epinephrine ,
norepinephrine ,thyroxine , digitalis and calcium ions.

15.  Resting heart, extract most of the oxygen from the
coronary blood as it flows through the heart muscles.
 when coronary blood flow fails to increase during
demands the strength of muscle diminishes rapidly
causes acute heart failure.

16.  When coronary flow to heart is occluded for a few
seconds to few minutes and then disoccluded the blood
flow increases to as high as 3 to 4 times normal.
 It remains high for a few second to few minutes.

17.  Stimulation of autonomic nerves to the heart can affect
coronary blood flow in 2 ways:

1. Directly
2.Indirectly

18.  Action of nerve transmitter substance on the vessels
will reduce the coronary blood flow through the release
of acetylcholine & nor-epinephrine.

19.  Sympathetic stimulation of nerve to the heart can affect
the coronary blood flow, by the release of nor-
epinephrine.