Every time that I have been seriously injured, typically I have not realized what a mess that I have made out of myself until the adrenaline starts to wear off. Depending on what you are concentrating on there is a period of time before you realize the sensation that you are experiencing is pain.
If you know something is hot and you cautiously touch or put the back of your hand near it to gauge just how hot it is, you can pull your finger or hand back before you are seriously burned. But if you inadvertently grab something very hot you will often not let go until after you are seriously burned especially if you are concentrating on something else.
This discussion about the nanoseconds it takes for your nerves to report back to your brain is a little silly. There is a much larger time period before your brain realizes what is going on after it receives signals from your nerves.
Also, my crews and I responded to many seriously injured people who were still alive and conscious when we arrived. Serious trauma and pain causes people to go into shock and they often cannot tell how serious their injuries are. So, we would be asked, “Am I going to die?” sometimes fairly calmly. A person’s expectations can affect their outcome, so we would almost always respond, “No, you are going to fine.”... even when we knew that they were probably not going to make it.
Just ask anyone who leaved their fingers behind while using a table saw. They usually notice the loose finger first.
As you probably already know: To speed response and thus reduce injury, pain signals are routed first to the spinal cord, rather than to the brain (meaning that there is a shorter pathway requiring less time for the nerve impulse to travel). Here's a very simplified explanation.
Regards,