It refers to the reflex leading to the discharge of the urine out from the urinary bladder through urethra.It is regulated by renal reflex which first allows fillings of the bladder and then permit
complete discharging its contents.The sphincter of the bladder have two types of the muscles;-
- External sphincter muscles.Which is made up of skeletal muscles inverted by somatic nerve fibres.It is under will.
- Internal sphincter muscle.Made up of smooth muscles inverted by antemonic nerve fibres.Also has inherent myogenenicity/intrinsic activity complete emptying is brought by contract of destrusor(urinary bladder )muscle and relaxation of sphincter.