Fig 1. Ascending and descending anatomical routes capable of transmitting bladder pain.
Primary sensory afferents detect noxious signals in the bladder and relay information to second order neurons in the lumbosacral spinal cord. Sensory information is transmitted to subcortical relay centers like the thalamus and parabrachial nucleus via three main ascending tracts, the spinothalamic tract, spinoparabrachial tract, and postsynaptic dorsal column. From here, the sensory and affective components of bladder pain are processed in a number of supraspinal regions that are highly interconnected with one another. Descending bladder pain information is transmitted to the PAG before being processed by the RVM and finally returning to the spinal cord where it acts on primary sensory afferents, spinal interneurons, and motor neurons.