A computer model for describing the effect of urethral afferents on simulated lower urinary tract function

A computer model of mechanical properties of the bladder, the urethra and t he rhabdosphincter, as well as their neural control is presented in this pa per. The model has a rather simple design and processes sensory information from both the bladder wall tension and urethral stretch. It is assumed tha t afferent signals from the urethra are involved in a sacral excitatory ref lex and a supraspinal inhibitory reflex. Pressure and flow signals that res emble experimentally measured normal human behaviour could be simulated wit h this model. From these simulations the relation between the neural contro l mechanisms used in the model and the neural control mechanism in vivo can not be judged entirely because similar behaviour could be simulated with mo dels that are based on different neural control mechanisms. Also behaviour that resembles detrusor overactivity was simulated with our model after an externally induced rise in detrusor pressure was added. Detrusor overactivi ty, sometimes in combination with urethral relaxation, can occur during a u rodynamic investigation. A possible explanation for this detrusor overactiv ity might be that the micturition reflex is triggered by unknown disturbanc es and is inhibited immediately after by the same mechanism that normally c eases voiding. The described model provides such a mechanism. Based on thes e simulations, therefore, it is concluded that urethral afferent signals mi ght be important in lower urinary tract control.