What causes radiation of the numbness/pain(?) to the left arm during angina?
A ‘radiation of pain’ is due to something that is called referred pain. Angina pectoris, which is what I suspect you are referring to (“Chest pain”) is caused when there is an inadequate flow of blood and oxygen to the heart. Your heart, being deprived of these essential needs, starts to obstruct the arteries in your heart. Your heart, in essence, begins to “hurt”. Since your heart is a viscera, which means that it is an organ in your body, it has very little nociceptors over the range of the entire organ. Thus, even the pain in your chest is actually considered ‘referred’, and it is referred to an area near the region so that you are made aware of it (Because that is the purpose of pain, to alert you to something that is wrong, referred pain to an area near the site of distress serves the same purpose). The way that pain is referred is due to the spinal nerves that connect to your heart, or to any other viscera in your body, and it receives nociception (the clinical word for pain, vs
