As the bladder fills, stretch sensors give you the urge to pee. But you can hold it, at least for a while. Fill the bladder, then empty it.
Bladder filling
Micturitionfill โ urge โ void
What's happening
The reflex: stretch receptors โ spinal cord โ the detrusor muscle contracts and the internal sphincter relaxes. You control the external sphincter on purpose. That is how you โhold it.โ
๐ท Reference image
A real labeled figure to compare with the interactive above.
The Micturition Reflex โ OpenStax, CC BY 3.0 (via Wikimedia Commons)
