True or false regarding blood supply of the heart

 True or false regarding blood supply of the heart

a) The circumflex artery is a branch of left coronary artery
b) There is a close correlation between myocardial oxygen consumption and coronary blood flow
c) Tachycardia cause decrease of duration of systole than diastole
d) Maximum blood flow in L. Coronary artery occurs in early diastole
e) Lacte cause dilatation of coronary artery

Answer

a.  T
b.  T
c.  F
d.  T
c.  F

Discussion

a.

• Coronary circulation has main two arteries 

1 Right coronary artery
2. Left coronary artery

Right coronary artery

• Arise from the right aortic sinus of the ascending aorta 
• It has sinu – atrial nodal branch 

• Right marginal branch 

• Posterior interventricular branch 

• Right coronary supplies blood to 

• The right atrium 

• Right ventricle 

• Sinu-atrial and atrioventricular node 

• The interventricular septum 

• Portion of the posterior part of the left ventricle 

Left coronary artery

• Arise from the left aortic sinus of the ascending aorta 
• It has 

• Anterior descending artery(anterior interventricular branch) 

• Circumflex branch 

• Left coronary artery supplies blood to the

• Most of the left atrium 

• Left ventricle 

• The interventricular septum 

• Atrioventricular bundle and its branches. 

b.

• When myocardial O2 consumption increased ( metabolic rate increase) coronary blood flow increased
•  Reduction of O2 level and increase metabolic products like CO2 , H+, K+, lactate, prostaglandins, adenine nucleotides leads to dilatation of the coronary artery 
• Increases coronary blood flow 

c.

• When the heart rate is 75 bpm 

• Duration of the cardiac cycle is about 0.8 S 

• Duration of systole is about 0.27 S 

• Duration of diastole is about 0.53 

• When the heart rate 200 bpm 

• Duration of the cardiac cycle is about 0.3 S 

• Duration of systole is about 0.16 S

•  Duration of diastole is about 0.14 S

d.

• During systole left ventricular pressure higher than the aorta 
• During systole blood vessel of the left ventricle is compressed 
• Blood does not flow during systole 
• During diastole blood flow to the left ventricle as pressure inside left ventricle is lower than the aorta