The Sensation of Pain

What is pain, really?

Thu Jun 16, 2022

The Sensation of Pain

When we cut our finger or scrape our knee, we say “Ow! It hurts!” and we describe that sensation as painful.

But what do we actually mean by that? What is pain and how is it felt?

Pain is an unpleasant sensory and emotional experience we feel when we hurt ourselves. When we cut our finger, the nociceptors (pain receptors) in our finger are activated and our nervous system transmits that signal to the brain.

Therefore, the sensation of pain is actually generated in our brain, though we experience it in a specific part of your body. The sensation of being “hurt” when we cut our finger is happening in the part of our brain mapped to our finger. This is why when we sleep, we do not feel pain. This is why anesthetic works. In other words, if we halt the transmission of electrical signals through your neurons at your finger to that specific part of the brain, you would not feel pain at all. Have you heard of Ibruopfen or Tylenol (Acetaminophen)? Those are the off-the-shelf painkillers we can get at the nearby drugstore and they operate exactly on this premise. Prostaglandin is a chemical released by injured or damaged cells. Nerve endings pick it up and respond to it, transmitting a signal to your brain and consequently, you feel pain. A painkiller like Ibuprofen, blocks the release of prostaglandin by inhibiting the enzyme COX (cyclo-oxygenase enzyme) responsible for synthesising it. Reducing the amount of that chemical reduces the signal and level of pain felt. (side note: different painkillers work differently.)

But if pain is felt in our brain, shouldn’t it all feel “similar”? Yet, we are able to somewhat accurately point out the part of our body that is hurting.

This ability arises because the signals from our receptors are transmitted to a part of our brain called the somatosensory cortex. As mentioned above, the sensation of pain occurs in the part of our brain mapped to that particular area.

And indeed, scientists have generated this neurological map, the Cortical Homunuclus, that tells us which part of our brain represents what part of our body.

Here is an illustration of this neurological map:

and a Cortical Homunuclus Model designed by Penfield.

The funny-looking model of man by Penfield has abnormal proportions because the size of the body parts in the model corresponds to how large the area of the brain is allocated to it. This allocation is actually not based on size as one might assume, but rather on relative importance. For example, the hands are much larger relative to the torso because the nerves from the hands end up connecting to a much larger area of the brain than the nerves from the torso. It makes evolutionary sense, as our hands needs to be more sensitive to our environment. We use our hands to grab food, make tools, do work etc, but our torso’s function is more for support and organ storage.

The somatosensory cortex and the varied allocation of brain area to different body parts allows us to identify where the pain is and how much it hurts. But this is just one small part of the story.

Pain is so complex. Think of how we use so many different words to describe different types of pain (stinging, throbbing, pulsing, sharp…..) Besides the sensory component, there is also the feeling component. The somatosensory cortex works in tandem with other systems in the brain, like the limbic and cognitive system, to give us the complex and highly varied sensation of pain. Ah, but that is another long, long story for another time.

Pain is a very fascinating sensation, one that accompanies sickness and disease and brings us much anguish and distress. At the same time, however, it is important to our survival.

I hope this short insight into this sensation was not a pain to read, but rather got you little more curious about the wildly interesting world of your brain. :>

Chloe
Subject: Biology (Neuroscience)

The Sensation of Pain

The Sensation of Pain

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