I2I0 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



INTERVIEW 



CMS H«o 

 75 

 60 



45 

 30 



'5 

 Q_ 



COUGH 



4 5 



MINUTFS 



FIG. 3. Tambour tracings of intravesical pressure obtained from a patient showing eflTects of 

 increased intra-abdominal pressure and of emotional stimuli resulting from a psychiatric inter- 

 view. [From Straub et a!. (29).] 



the Stretch imposed b\' fiUing to the postural reflexes 

 of skeletal muscle. The tonus limb is thought by some 

 (8, 9) to represent an interplay between an excitatory 

 reflex (tonus) and an inhibitory reflex (adaptation or 

 accommodation), comparable broadly to the short- 

 ening and lengthening reaction of extensor muscles. 

 According to this analogy, the degree of bladder 

 tonus is neurally determined. Denny-Brown & Rob- 

 ertson attributed the basic neural mechanism of 

 tonus to the plexus of neurons lying on the bladder 

 wall whereas Langworthy's concept was a neural 

 mechanism analogous to that controlling the myotatic 

 reflex of skeletal muscle, a spinal refle.x controlled 

 by the brain stem. Clinical workers, with tlie ex- 

 ception of Nesbit and his co-authors (26, 27), either 

 have made no interpretation or have accepted the 

 neurogenic origin of bladder tonus explicitly or im- 

 plicitly. 



Absence of Higher Control of Bladder 1 one 



In figures 4 and 14 to 16 is presented a series of 

 experiments in which cystometrograms were ob- 

 tained from intact unanesthetized cats and from 

 the same or other cats after segmental transec- 

 tions at various levels of the neural axis, the deter- 

 minations being made after the effects of ether anes- 

 thesia had dissipated. It will be observed from the 

 take-off point of the arrows denoting micturition 

 that the various transections profoundly altered the 

 micturition-reflex threshold and hence the excitabil- 

 ity of the micturition reflex. Transections at some 

 levels increased micturition-reflex excitability over the 

 pre-existing state; at other levels, transection de- 

 creased the threshold. In the whole series of experi- 



ments, the thresholds ranged from 4 ml (intercollicular 

 decerebration) through 66 ml for the intact cat to 

 complete failure of the refle.x in acute spinal prepa- 

 rations. These threshold changes will be correlated 

 with levels of transection in a later section. 



The point at issue here is the comparison within 

 each diagram (representing a single animal) of Seg- 

 ment II up to the point of micturition. For each 

 animal, the tonus limb is identical, within the limits 

 of experimental error, in the normal state and after 

 each of the sequential transections used in the par- 

 ticular experiment. Although transections at various 

 levels between a hypothalamic level and the spinal 

 cord' varied the micturition threshold from a few 

 milliliters to complete failure of micturition, the 

 operations had no efl'ect on bladder tonus. It is 

 concluded therefore that bladder tonus, unlike the 

 micturition reflex, is not subject to either facilitation 

 or inhibition from supraspinal levels. If bladder tonus 

 is a reflex, it is unique among reflexes in not being 

 subject to higher control. 



The literature contains many reports of changes in 

 intravesical pressure following stimulation of various 

 brain-stem and cortical structures, and such changes 

 have usually been identified with tonus. An alterna- 

 tive explanation is that they are fractional mani- 

 festations of the micturition reflex, elicited by a frac- 

 tional activation of the complex neural apparatus 

 controlling the e.xcitability of this reflex. Striking 

 changes of intravesical pressure (fig. 3) ha\e also 

 been induced in man by stiinuli with emotional 

 significance (29). Whether these are tonus changes or 



' Langley & Whiteside (181 made a s'milar observation after 

 spinal transection in the dog. 



