All parts of the brain › Functions › Bladder control

What part of the brain controls the bladder?

The pons runs it; the frontal cortex decides when. Its pontine micturition centre (Barrington’s nucleus) switches the emptying reflex, squeezing the bladder wall and opening the sphincter together, while the prefrontal cortex, insula and cingulate gyrus hold it back until you choose to go. [1][2][3]

The 3D brain needs JavaScript. The list of parts still says what each one does for bladder control.

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All 7 parts are lit together. Drag to turn, pinch or scroll to zoom, tap a part on the brain or a name in the list to focus it; .

Bladder control: 7 parts lit

Pons, midbrain, spinal cord (central canal), insula, cingulate gyrus, prefrontal cortex and hypothalamus. Tap one to see where it is and what it does.

The parts and their roles

Its upper (rostral) part holds the pontine micturition centre, also called Barrington’s nucleus. Its neurons stay quiet while the bladder fills and fire when it is stretched and the go-ahead is given, driving the spinal neurons that contract the bladder’s detrusor muscle and relaxing the urethral sphincter. It has no separate shape on this model, so the whole pons lights. [1][2] Where is the pons?
Its periaqueductal grey is the relay station: bladder signals climb the spinal cord to it, and it passes them on to the micturition centre and the cortex while also carrying signals from the higher brain back down, and the midbrain also holds an area that inhibits the reflex. [1][2][4] Where is the midbrain?
Stretch signals from the bladder wall reach its sacral segments through the pelvic nerves; parasympathetic fibres from the sacral cord contract the detrusor, sympathetic fibres from the lumbar cord act on it too, and the pudendal nerve from the cord works the external sphincter, the one you relax on purpose. [2][5] Where is the spinal cord?
Bladder signals passed on by the periaqueductal grey are registered in the insula, where they form the normal sensation of the urge to go; the insular cortex is among the areas the micturition centre works with. [3][1] Where is the insula?
Its front part, the anterior cingulate, monitors the filling and the urge, and brain imaging shows the frontal part of the cingulate gyrus taking part in bladder control. [3] Where is the cingulate gyrus?
Keeps the reflex held back until the decision to go is made here; pathways from the prefrontal and insular cortex reach the micturition centre and the hypothalamus. Imaging studies found this control is mostly on the right side of the brain. [3] Where is the prefrontal cortex?
The micturition centre works with the hypothalamus: its posterior part holds an area that eases urination, and voluntary control runs partly through a link between the frontal lobe’s septal area and the hypothalamus’s preoptic area. [2][1][3] Where is the hypothalamus?

How they work together

There are two phases. In the storage phase the bladder relaxes and fills while the sphincters stay shut; in the voiding phase the detrusor contracts and the sphincters open. In an adult the bladder holds about 300–500 ml, and a filling of about 300–400 ml normally sets off the reflex contraction. [2][5]
The loop runs bladder → spinal cord → periaqueductal grey → pontine micturition centre → back down the spinal cord to the bladder. While you are holding on, the periaqueductal grey keeps the centre switched off; once the fullness signal passes a threshold and the cortex gives the go-ahead, the centre fires maximally and voiding runs to the end. [3][2][1]
The wish to go can be put off because the external sphincter is a skeletal muscle under voluntary control through the pudendal nerve, while the bladder wall itself is smooth muscle that you cannot squeeze directly. [2]
Honest limit: the pontine micturition centre, the periaqueductal grey and the preoptic area are small nuclei with no separate shape in this atlas, so the whole pons, midbrain and hypothalamus light; much of the circuit was mapped in animals, and the cortical roles come from human brain imaging that shows activity, not exact wiring. [1][3]

Sources

Facts describe anatomy and normal function only. A part lit here takes part in bladder control; it does not do it alone, and it does other jobs too. The 3D model is the adult male BodyParts3D brain (credits and licence); on it the brainstem includes the midbrain, pons and medulla, so lighting the brainstem lights all three.