A shot to the chest that goes high and impacts in the throat area is pretty devastating.
Theres not as much flesh between adams apple and spine as anywhere else and no large bones in the way.
A hit on the inside surface of the spine where it connects up with the skull is more than likely going to shut down all body movement, a sufficiently hard hit will cause internal decapitation as surely as a automobile wreck.
A Vietnam era sniper once told me that neck shots were better than head shots, partly due to possible deflection from a helmet I suppose, but mainly because he had once hit a NVA square in the head and blown most of the man's brain out and the body continued walking in a circle firing the AK till it just fell over.
A Medic told him that the last message from the brain to the spinal cord would continue to motivate the body. It was best to break the connection between brain and body. Then the target will simply drop and never again move even if the subject lives for minutes or hours.
I have seen an accident victim with half her head gone moving about on a stretcher and gabbing up a storm as if dancing at a party. That may be the thoughts going through what was left of her brain.
Several people in my home town have survived bullets in the brain. One suicide attempt where a man held a .22 rifle muzzle between his eyes and pressed the trigger with his toe resulted in the bullet simply sliding between the halves of the brain and flattening on the inside of his skull.
Another was shot in the back of the head by a woman when he pulled a gun on her husband. He had started to turn his head when the gun went off. A .38 Special bullet slid under his brain and came out under one eye. He was a bit messed up but suffered no permanent harm other than requiring surgery to repair facial muscles and nerves.
The heart is a pretty tough muscle. The major cause of death from a wound to the heart is leakage of blood into the cardial sheath around the heart, which upsets the balance and makes each heart beat less productive till not enough blood is pumped to sustain life.
Is the sheath is torn a simple penetration of the heart muscle is survivable.
A local man (a door gunner around 69-71) took two 7.62 bullets to the heart and survived, both bullets being found inside one heart chamber. That was at long range and I expect body armor slowed the bullets down.
A bullet through the pulmarnary aorta will kill far more certainly than a bullet to the heart.
The renal aorta is another quick kill, with unconsiousness coming even more quickly. Blood pressure drops near instantly.