CENTRAL CONTROL OF THE BLADDER 



I2I5 



bladders were observed and encouraged by careful 

 nursing. Since World War II, the orientation, in- 

 cluding surgical intervention, has been toward con- 

 trolling o\eractivity of the bladder. 



The neurophysiologist draws an analogy between 

 the myotatic reflex of skeletal muscle and the mic- 

 turition contraction, both being reflexes in response 

 to stretch and both being relati\ely sustained ac- 

 tivities. He thinks of such reflexes in higher animals 

 as depending not on a simple reflex arc but on such 

 an arc played upon by facilitation and inhibition 

 from several levels of the brain stem. A moment's 

 reflection suffices to show that a reflex arc inhibited 

 from the cerebral cortex is not a typical pattern for 

 either visceral or somatic mechanisms, nor does 

 this oversimplified concept afford any explanation of 

 the period, lasting clays, during which the spinal re- 

 flexes are depressed. Physiologically, posttransection 

 areflexia or hyporeflexia (spinal shock) are ascribed 

 to the blocking of descending facilitatory impulses, 

 missing from the urologists' schemata. Recent phys- 

 iological investigations seem to indicate that the 

 higher control of the micturition reflex and the 

 myotatic reflexes of antigravity muscles can, mutatus 

 mutandis, fit into the same framework. 



Levels of Bladder Control 



The following account is based upon and extends 

 the classic, but neglected, observation of Barrington 

 (i, 2) which proves that the upper pons contains a 

 powerful micturition facilitatory area. Some of the 

 same observations were also made by Langworthy 

 and his co-workers (19). However, for the sake of 

 simplicity of presentation, and because their experi- 

 ments involved anesthesia and their interpretations 

 were dififerent, the following account is based upon 

 a single set of experiments (31, 33). The levels of 

 transection referred to in the text are shown in figure 

 13. Description will be in terms of the most rostral 

 level maintaining continuity with the final common 

 path rather than the transection yielding the prepara- 

 tion. 



ANTERIOR PONTINE PREP.'VR.-VTiON. When the spinal 

 cord of the cat is divided, no amount of fluid intro- 

 duced into the bladder will elicit even the slightest 

 micturition contraction. Complete vesicle areflexia 

 exists. However, when the brain stem is transected 

 just above the pons or at the classic intercollicular 

 level, quite the opposite happens; not only does the 

 micturition refle.x occur, but the threshold volume is 



TRANS- 



hypothalamic / 

 decerebration / 



supracollicula'r 

 decerebration 



subcollicular 

 decerebration 



\intercollicular 

 decerebration 



Fio. 13. Schematic representation of levels of brain-stem 

 transection. SC, superior colliculus; IC, inferior coUiculus; M, 

 mammillary body; P, pons. [From Tang (31).] 



only a fraction of the normal and the detrusor con- 

 traction is powerful and sustained (fig. 14). If a 

 second transection is inade a few millimeters caudally 

 (fig. 15), if the anterior pontine tissue is cooled 

 (East,N.R.,J. J. Milford & T. C. Ruch, unpublished 

 observations) or if the appropriate pontine locus^ 

 is focally destroyed, the micturition reflex is no longer 

 elicitable — the preparation is virtually a spinal animal 

 in respect to micturition. Thus, as Barrington rightly 

 concluded, the anterior pons gives origin to a de- 

 scending tract which facilitates the spinal micturition 

 reflex arc. When this descending pathway is the only 

 remaining suprasegmental influence, the micturition 

 reflex is so facilitated that the threshold volume is 

 but a fraction (typically one-sixth) of that required to 

 trigger the reflex in the intact cat. From these experi- 

 ments it may also be concluded that the neural struc- 

 tures rostral to the anterior pons exert a net, power- 

 ful, inhibitory action on this reflex. 



Although the level of control is slightly more ros- 

 tral for the bladder, there is a basic similarity to the 

 tonic brain-stem influences on other visceral struc- 

 tures (e.g. blood vessels) and on the postural refle.xes 

 of the antigravity muscles (decerebrate rigidity). 



ROSTRAL MIDBRAIN PREPARATION. If a supracollicular 

 transection is performed a few millimeters higher, 

 along the line so labelled in figure 13, an inhibitory 



' Bilateral focal lesions in the dorsal tegmentum at the 

 isthmus level, immediately ventral to the lateral angles of the 

 periventricular gray matter, destroy the pontine center (33). 



