This might be a rather odd example, but when I’m peeing, I can pinpoint the EXACT location I feel my pee actually leaving my tip, if that makes sense. How come I can’t feel my bladder, or the stream going through the tube, thanks.
In: Biology
Actual ELI5 TL;DR: We can, but not equally for all organs, usually only when things are changing or going wrong, and it’s harder to tell where sensations are coming from because the nerve endings are more spread out + we can’t see exactly where things move inside us.
There are a few questions/assumptions wrapped into this question:
1. Can we consciously sense internal stimuli?
2. How specifically can we localise or feel where exactly sensations come from?
3. How does this work for the genitourinary system, like your example?
Broad answers:
1. Yes! This is called ‘interoception’, the sensations inside us. More specifically, a type of interoception is ‘visceroception’ or feeling our visceral organs (e.g. heart, lungs, kidneys, GI tract, etc.). You won’t feel the brain at all as it doesn’t have sensory nerves (even though it’s the source and destination of most sensory nerves from elsewhere).
As others mentioned, sensations are based on change in stimuli, and our brain’s interpretation of what’s going on and how relevant that is (notice the sensations of sitting in your chair or your tongue in your mouth and it literally feels different than when you’re not attending to it). So change and relevance matter, meaning most unchanging and irrelevant sensations are filtered out to minimal, vague perceptions that are only relevant when things are going wrong, causing discomfort or pain.
2. Localising sensory signals is a practiced skill based on sensory feedback and integrating many senses. When you feel something in a specific place, it’s based on a combination of how tightly packed the sensory nerve endings are in that area (most sensitive around lips, genitals, fingers; least across areas like the back and legs) and how much we can use feedback from the world or other senses to check. Internal sensors vary but are generally a lot more diffuse.
3. Based on the above, a body-temperature stream of smoothly flowing urine does not create much physical stimulation and little sensation change, plus we can’t see it, so our brain’s don’t have the feedback to learn where specific sensations are coming from. When it reaches the end of the urethra and exits the body, there’s more changing stimuli, more sensory nerves, and we can see it so it’s a much more specific localised sensation.
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