44-during respiration a- inspiration is a passive movement with no aid from muscles x b- external intercostals muscle is an inspiratory muscle (c-) during inspiration the diaphragm is pulled down d - forced expiration is aided by relaxation of the abdominal muscles a- arise from the arch of aorta F b-) each gives atrial and ventricular branches c- doesn't supply the conducting system xd - anastomose with each other at anterior surface of the heart 59- if the left coronary artery is blocked, which of the following part is mostly affected a- the sinuatrial node (b) the left atrium c- the right ventricle atrioventricular node.