Later, the subject is bitten by a rattlesnake, but remains healthy, thanks to your injection. This is an example of a. active immunity. The left atrium and left ventricle contract roughly simultaneously followed by the right atrium and right ventricle. The left and right atria contract roughly simultaneously, followed by the left and right ventricles. Left ventricle 1st, left atrium 2nd, right ventricle 3rd, right atrium 4th.
Mammals have a two-chambered heart.
All arteries carry oxygenated blood. All veins carry deoxygenated blood. All arteries carry blood to the heart. All veins carry blood away from the heart. Imagine that you inject a rabbit with a small amount inactivated smallpox virus.