Final answer:
An individual can voluntarily empty their bladder by contracting the external urethral sphincter. This action is part of voluntary urinary control, which is necessary for overriding the automatic micturition reflex until a suitable time for urination is chosen.
Step-by-step explanation:
An individual may choose to empty the bladder prior to the initiation of the micturition reflex by contracting the external urethral sphincter muscle.
The detrusor muscle in the wall of the bladder is composed of smooth muscle fibers that are involuntary but influenced by both the autonomic and somatic nervous systems. During the process of micturition, parasympathetic neural outflow results in the contraction of the detrusor muscle, while the internal urethral sphincter, which is also involuntary, relaxes. However, it is the voluntary contraction of the skeletal muscle within the external urethral sphincter that allows for conscious control over the timing of urination.
As the bladder fills and stretches, the urge to urinate becomes stronger. The ability to override this urge and maintain urinary continence relies on consciously contracting the external urethral sphincter muscle. However, as the bladder reaches its capacity at around 300 to 400 mL, maintaining continence may not be possible, leading to incontinence.