Autonomic Innervation of the Urinary Bladder

00:01 Let's have a look at the autonomic innovation of the bladder.

00:05 And we spoke about the complex anatomy of the bladder in how all of the detrusor muscle can't contract at the same time.

00:12 So now let's explore that.

00:14 Here we have the detrusor muscle.

00:16 We have the internal urethral sphincter, and here we have the nerves that are going to supply it.

00:21 So we have via the inferior hypogastric plexus.

00:24 We have parasympathetic innovation that goes to the detrusor muscle and to the internal urethral sphincter.

00:31 We also via the inferior hypogastric plexus have nerve fibers that are sympathetic in nature, going towards the same region, the detrusor muscle and the internal urethral sphincter.

00:44 Now, remember, parasympathetic and sympathetic are associated with rest and digest, or fight and flight respectively.

00:52 So they're going to have opposing effects on the function of the bladder.

00:56 So let's imagine the sympathetic is in charge and what's happening to the bladder and the internal urethral sphincter.

01:03 Remember, the sympathetic is associated with fight and flight.

01:08 So during that process, you don't want to be micturating.

01:11 So this is the process where you're going to be storing the urine within the bladder.

01:16 So to do that, you need the detrusor muscle to relax as it relaxes. So urine can fill the bladder and it can expand.

01:24 As that's happening, you want the internal urethral sphincter to contract to prevent the outflow.

01:31 We've parasympathetic in charge, you're actually able to micturate to go to the toilet.

01:36 In this time, you want the detrusor muscle to contract, and that will force through an open, relaxed internal urethral sphincter for the urine to release and pass out of the urethra.

01:49 At this time, actually, you want the external urethral sphincter to also be under control.

01:56 So here we can see the interplay between the parasympathetic and the sympathetic nervous systems.

02:02 And that will cause the urge or the lack of an urge to go to the toilet to micturate.

02:08 The parasympathetic will increase that urge but you still won't go to the toilet.

02:14 You'll only go to the toilet once you then consciously decide to relax the external urethral sphincter through function of the pudendal nerve.

02:23 Normally, under sympathetic control, the pudendal nerve will cause the external urethral sphincter to contract and to prevent urine flowing through.

02:32 Even though the parasympathetic is causing the internal to relax the detrusor muscle to contract, you are in control.

02:41 And you can then help to either contract or relax that external urethral sphincter through function of the pudendal nerve.