Friday, January 30, 2015

Micturition reflex and types of bladder



Rather than going into exaggerated details..I will only point the important facts

1.     When urine starts collecting within the bladder. The detrusor muscle is stretched. This is detected via stretch receptors and is carried by the sensory nerve to the spinal cord.

2.     The reflex arc root value is S2 to S4, from this parasympathetic fibres arise, which causes contraction of detrusor muscle.

3.     This arc is under the control of the higher centers ( frontal lobe and pons), which can either FACILITATE or INHIBIT this reflex arc.

The clinical aspects to this are-
1.     Atonic bladder- This happens when only the sensory pathway is destroyed. Example the posterior cord lesions where all sensory tracts are involved like tabes dorsalis.
The bladder stretches to its maximum (because of the absence of stretch sensation) and suddenly there is overflow of urine

2.     Automatic bladder- Think of this bladder like that of an infant. The child voids urine without any conscious control. The micturition reflex is intact..but the higher centers are not active! Hence as soon as the stretch reflex becomes strong enough the person voids urine irrespective of the social setting.
Example- cord lesions above the level of s2 .


http://medicowesome.blogspot.in/2014/11/remembering-autonomic-innervation-of.html

-M-




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