A heart attack occurs when a __________ is occluded and a portion of the heart is deprived of blood supply.

A heart attack, also known as a myocardial infarction, occurs when a coronary artery is occluded. The coronary arteries are responsible for supplying blood to the heart muscle itself. When one of these arteries becomes blocked, typically due to a buildup of fatty deposits or plaques, blood flow to a part of the heart is restricted. This means that the affected heart muscle does not receive the oxygen and nutrients it needs to function properly. If the blockage is not resolved quickly, this can lead to damage or death of heart tissue due to lack of blood supply, resulting in a heart attack.

The other options provided do not play a role in supplying blood to the heart muscle. The superior vena cava is responsible for draining deoxygenated blood from the upper body back to the heart, while the brachial artery primarily supplies blood to the arm, and the radial artery supplies blood to the forearm and hand. None of these arteries are involved in the direct blood supply to the heart muscle, which is why they are not the correct answer in this context.