A question for the docs here...

[il Padrino Ute]

my 12 year old asked me how the bladder lets him know that he has to pee. I couldn't even come up with anything to fake an answer, though that no longer works with him.

A little help would be appreciated.

If anyone else knows the answer, feel free to respond.

[NorthwestUteFan]

Off the top of my head (and it has been at least a dozen years since I had Anatomy), the bladder stretches to varying degrees when it is filling/full. There are nerves in the wall of the bladder that sense the tension that occurs when the cell in the bladder wall are stretched. They work somewhat like a strain gauge.

We have nerves in our ligaments which provide the same feedback to control the position of our joints (proprioception). Similar nerves in the walls of blood vessels to give us feedback on blood pressure.

[ERCougar]

NWUF is essentially right. Patients with spinal cord injury, for instance, have to insert a catheter periodically to drain their bladder because they lose this feedback. One of the signs of cauda equina syndrome (compression of the end portion of the spinal cord) is overflow incontinence, where the bladder fills and never empties, just continuing to dribble out urine as the kidneys produce it.

[il Padrino Ute]

Thanks for the info guys. Very interesting stuff.