Here is a diagram, look at the big blue artery in the middle of the screen. It carries blood to the lungs, then pulmonary veins return blood back to the left atria and drops in the left ventricle. The left ventricle pushes blood up the aorta that branches off to feed your brain. If blood is stopped at the big blue artery, where are you getting blood to feed the brain? https://i.pinimg.com/originals/9c/02/b0/9c02b084ce9a75fee1be678b447c02f0.jpg

Here is a diagram, look at the big blue artery in the middle of the screen. It carries blood to the lungs, then pulmonary veins return blood back to the right atria and drops in the left ventricle. The left ventricle pushes blood up the aorta that branches off to feed your brain. If blood is stopped at the big blue artery, where are you getting blood to feed the brain? https://i.pinimg.com/originals/9c/02/b0/9c02b084ce9a75fee1be678b447c02f0.jpg