Stroke can cause a range of incontinence problems. This occurs as a result of the damage to the brain and bladder communication channels. This post explores how it happens. Another post will explore what bladder problems stroke can cause.
Table of contents
- The bladder control mechanism
- The role of the two gates in the continence
- How the brain communicates with the bladder in bladder control
- How stroke can disrupt brain-bladder communication
The bladder control mechanism
Figure 1 depicts the inside of a bladder. The tubes (ureters) transport urine from our kidneys to the bladder. The bladder can store about 450-500ml of urine. Its wall consists of a strong muscle layer, called “detrusor muscle”. This muscle contracts to squeeze out urine when the specialized brain areas send messages to do so. However, the brain should receive information from the stretching bladder wall about the increase in urine volume. This happens through a web of nerve endings that populate the outer layer of the bladder wall. The message goes up to a place at the lower part of the brain stem.
The role of the two gates in the continence
Go through Figure 2. Find out the two control gates; these are named “sphincters” because they act like valves.
- The inner gate (named inner urethral sphincter)
- The outer gate (named outer (external) urethral sphincter).
We can find these gates near the tapering lower end of the bladder. As soon as the transit center at the spinal cord receives approval from the brain, it messages the gates open and the bladder wall contract. As a result, urine will flow out.
How the brain communicates with the bladder to avoid continence problems
The brain owns a widespread network covering every minute area of our body as shown in Figure 3. Obviously, it also includes the bladder and bladder gates.
Brain areas that prevent continence problems
Figure 4 depicts the specific brain areas specialized in communicating with the bladder and its control gates.
When the bladder wall muscle, detrusor, stretches with urine getting filled, the nerve network that covers its wall messages the center at the Pons (Figure 4) via the spinal cord. This center, named “Pontine micturition center”, seeks permission from its higher centers to activate the peeing reflex which it normally does. Under normal situations, the higher centers veto the Pons’ center’s request until a suitable time and place find to pee. In this way, the higher centers suppress this urgent message to contract from the bladder wall and to relax the internal gate.
In contrast, the other route transports messages to inhibit the wall contraction and close valves.
Stroke can disrupt brain-bladder communication causing continence problems.
Stroke kills neurons in areas where blood supply is stopped. It happens either due to a blockage to the supply or rupture of a carrying vessel. The former is called “ischemic stroke” and the latter is called “hemorrhagic stroke”. These stroke types are discussed in this post. When the disruption to the blood supply occurs to the areas that are responsible for peeing, peeing problems result. The next post discusses what types of bladder problems stroke can result in.