Afferent fibres (Tl2-S4) record changes in pressure within the bladder and tactile sensation in the genitalia. The efferent pathways.
Disorders of micturition
Bilateral UMN lesions cause frequency of micturition and incontinence. The bladder is small and unusually sensitive to small changes in intravesical pressure. LMN lesions (which must be bilateral to cause urinary symptoms) cause a flaccid, atonic bladder, which overflows without warning.
Frontal-lobe lesions (e.g. dementia, hydrocephalus) cause a disturbance of awareness of micturition, resulting in incontinence particularly in an ageing population.
Failure of erection of the penis (or clitoris) and ejaculation is caused by bilateral upper or lower motor lesions. Depression is also a common cause of impotence. Endocrine aspects of impotence.