Why Do Heart Attacks Cause Arm Pain?

Interactive Transcript

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spk_0 When someone has a heart attack, they often clutch their left arm in pain,

spk_0 but the heart is in the chest, not the arm. So what's up? I'm Cameron, and this is MinuteEarth.

spk_0 When we feel pain, it's often because pain receptors in skin sensed that something was wrong,

spk_0 like a cut or a burn. In response, they generate a pain signal that travels to the brain along a

spk_0 chain of three nerve cells. The first cell in the chain generates the signal, then carries it to

spk_0 the spinal column, where it enters through one of the vertebrae. There, it links with a second neuron

spk_0 that carries the signal upward toward the thalamus in the brain, where it links with a third neuron

spk_0 that stimulates a specific region in the brain's sensory cortex. At this point, your brain creates

spk_0 the feeling of pain. The sensory cortex has places for feeling most parts of the body,

spk_0 like hands and feet, with large areas devoted to the most sensitive parts. But little or none of

spk_0 the sensory cortex deals with pain from internal organs. This doesn't mean the organs can't send

spk_0 pain signals anyway. When pain signals from a hurt organ get to the spinal cord, they are often

spk_0 forced to merge onto pain pathways from other, more sensitive body parts. Specifically, pain from

spk_0 an ailing heart often gets funneled onto nerve pathways in the spinal cord that carry sensations

spk_0 from the arm, which in turn light up the part of the brain that senses arm pain. This is why people

spk_0 tend to feel crushing pain in their left arms during a heart attack. Usually, at least, scientists

spk_0 don't really understand why, but some brains interpret heart pain as coming from the arm,

spk_0 while others interpret it as coming from the jaw. The pain is real, but the brain just doesn't have

spk_0 a good way of knowing exactly where it came from. This signal merging problem doesn't just happen

spk_0 with heart pain. Pain signals from the liver tend to merge onto tracks that end up in pain centers

spk_0 for the neck, and pain from the kidneys can merge onto tracks from the thighs. But much of the time,

spk_0 pain from organs is just felt in nearby skin and muscles due to the way that nerve paths merge.

spk_0 This phenomenon is called referred pain, and it seems to be an unavoidable quirk of the way

spk_0 that nerves are wired. There's still a lot to learn about how the brain interprets organ pain,

spk_0 but the more scientists learn, the better we will get at mapping the tracks of our pain trains.

Why Do Heart Attacks Cause *Arm* Pain?