Urinary control

The detrusor, whose smooth muscle fibres comprise the body of the bladder, is innervated mainly by parasympathetic nerves which are excitatory and cause the muscle to contract. The internal sphincter, a concentration of smooth muscle at the bladder neck, is well developed only in the male and its principal hmction is to prevent retrograde flow of semen during ejaculation. It is rich in aj-adrenoceptors, activation of which causes contraction. There is an abvmdant supply of oestrogen receptors in the distal two-thirds of the female urethral epithelium which degenerates after the menopause causing loss of urinary control. 

By the age of 4-5 years many children have been toilet-trained successfully and have adopted an adult pattern of urinary control. This is also characterized by the absence of involuntary or uninhibited detrusor contractions during bladder fiUing. Even if the bladder is full and there is a strong desire to void, no bladder contractions will occur. With micturition, coordinated relaxation of the external urethral sphincter takes place. Therefore, bladder emptying is under low intravesical pressure in children and adults. 

Nonneurogenic bladder-sphincter dysfunction is thought to originate from behavioral factors that affect toilet training and inhibit the maturation of normal urinary control. Since the gastrointestinal tract plays a prominent role in lower urinary tract dysfunction, the term dysfunctional elimination syndromes (Koff et al.l998) is applied, if functional bowel disturbances are associated in terms of chronic constipation and encopresis. 

If abnormalities of toilet training and aberrations in the development of normal urinary control persist, pathologic significance increases as the child becomes older. 

Muellner SR (1960) Development of urinary control in children. JAMA 172 1256-1261... 

One of the most successful commercially available implantable microelectrode arrays is the deep-brain stimulator. Deep-brain stimulation (DBS) uses chronically implanted electrodes to treat neurological conditions such as movement disorders. Electrodes deliver high-frequency electrical stimulation to targeted regions of the brain to treat symptoms of Parkinson s disease. Implantable visual prostheses promise to restore vision by providing stimulation at the retina, optic nerve, or visual cortex. Cochlear implants include an electrode array implanted in the inner ear to stimulate the auditory nerve. Other commercially available implantable neural interfaces include neurostimulation systems for treatment of chronic pain or urinary control. 

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