AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 2 225-R230, Copyright © 1986 by American Physiological Society
Urinary bladder function and its control in healthy females
D. J. Griffiths, C. E. Constantinou and R. van Mastrigt
Recordings in eight healthy female volunteers of bladder (detrusor)
pressure and flow rate, obtained during bladder filling and during voiding,
both through the urethra and through a catheter, demonstrate that a model
of bladder function in which the detrusor muscle is considered as
completely passive during filling and fully activated during voiding is
inadequate. Assessment of the detrusor contraction strength by a new method
(described in APPENDIX A) shows that in ideal normal voidings the
contraction strength rises to values of 11-24 W/m2 and is sustained or
rises slightly until the bladder is empty. During unstable detrusor
contractions, which even in these healthy women are observed during bladder
filling and also during inhibited voidings through the urethra, the
contraction is weaker. During voidings through a catheter the detrusor
contraction is weak, variable, and fades away before the bladder is empty.
An elementary feedback analysis demonstrates that the effect of the
micturition reflex governing detrusor behavior differs according to whether
or not voiding is taking place. The reflex does not lead to a simple on-off
mechanism but to a more complex behavior that is consistent with the
observations and that appears to be important for the understanding of
pathological obstructed micturition.
