Definition
Urge to urinate describes the feeling of having to urinate. This is in itself a normal function of the bladder, which begins with increasing filling. However, if the urge to urinate is unusually strong, this is an indication that there may be a disorder in the body or in the control circuit of the reflex to urinate.
Physiological development of the urge to urinate
One and a half liters of urine are normally excreted per day, depending on the individual drinking amount. This is produced by the kidneys, which filter the blood and transport waste products (urinary substances) out of the body through urine. The urine is stored in the urinary bladder, which can store up to 900 ml of urine, depending on the height of the person.
The urge to urinate, however, sets in much earlier, namely from a bladder filling of 300 ml. This urge to urinate is caused by the increasing stretching of the wall of the bladder due to its filling, as the increase in tension is detected by receptors, which in turn are connected to nerves. These nerves transmit the information about the filling state of the bladder to the brain, where the urge to urinate is then triggered and consciously perceived.
Physiologically, the difference between the filling level of the bladder when the urge to urinate begins and the maximum bladder capacity provides a certain amount of leeway, so that one does not have to urinate immediately when the urge to urinate begins. In addition, the urge to urinate can be influenced in a healthy person to such an extent that it is possible to hold urine despite a full bladder and an existing urge to urinate (continence). The muscles of the pelvic floor and also the external bladder sphincter muscle (Musculus sphincter urethrae externus), which can be controlled arbitrarily and consciously, are responsible for this. The emptying of the bladder (micturition) thus takes place in the interplay between the increase in pressure in the bladder and the slackening of the pelvic floor muscles and the external bladder sphincter muscle. This micturition reflex is controlled centrally in the brain and, due to the complex interconnection, it has many possibilities for a disturbance within this interaction.
