Say you get an injection and the site has been anesthetized beforehand with a topical numbing cream, why is it that you can still feel the pressure? Is the pressure sensation not associated with nerves? If not, how does your brain detect pressure sensations?
P.S. I’m not sure if “numbed” is a word but I couldn’t think of another way to say it lol.
In: Biology
>Is the pressure sensation not associated with nerves?
It is, but not the same nerves that carry pain signals. There are different nerves that do different things. The local anesthetic blocks the nerves that carry pain signals but not the nerves that carry the signals for pressure or mechanical stress, so you don’t feel pain, but you can still feel other sensations.
Different nerves for different types of sensation! This is a super fascinating area within sensation/perception, but basically we have different types of neurons to tell us about different kinds of stimuli. Some detect heat, others pressure, and so on. “Pain” casually understood is but one type of physical sensation.
Certain nerves detect pain and other nerves detect pressure. Local anaesthetics block pain nerves, so you can feel everything but pain.
The short answer is that you have a bunch of different groups of nerves that do different things. Some of them send signals for your muscles to move, some of them detect pain, some of them detect hard pressure, some of them detect light touch, some detect temperature. And they’re not all in the same place. So doctors numb the pain ones and leave the rest alone.
A doctor can probably explain this 100% better – but let me try; we don’t have 5 senses, that’s not even remotely true. You have a lot more. For example – you just “know” where the position of your limbs are in relation to “you”. You also know if the temperature just fell 2 degrees.
In the same way – pressure and pain is not exactly the same. Again, a doctor will probably humble me explaining how I’m or saying it all wrong, but as far as I understand it, that’s the essence.
As for stitches depending on where you are they apply said numbing agent. In my experiences (59 stitches total over 9 injuries) it’s not pressure from the numbed area, it’s everywhere else. Surface layer anaesthetic doesn’t permeate deep enough to affect the nerves standard freezing agent delivers. The pressure is literally from the added fluids and that numbing paste doesn’t reach your bones or anything else but a few sensitive layers of skin.
One is for the tiny needle (paste anaesthetic), the other is for the thread coming through your body (freezing agent).
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