The document summarizes the nerve supply and physiology of micturition (urination). It discusses: 1) The sympathetic, parasympathetic, and somatic nerve pathways involved in filling and emptying the bladder. Parasympathetic nerves excite the bladder during filling while sympathetic nerves inhibit it. 2) The sensory afferent fibers (A-delta and C fibers) that provide sensation from the bladder. C fibers are not normally active but can become hyperactive in pathological conditions like spinal cord injury. 3) The peripheral efferent pathways - sympathetic nerves inhibit the bladder and excite the urethra, while parasympathetic nerves excite the bladder and relax the urethra. Somatic pathways contract

1. Nerve Supply of Bladder and
Physiology of Micturition
Dr.Roshan V Shetty

4. NERVE SUPPLY
SensoryMotor
• Sympathetic Parasympathetic
T11, T12, L1, L2 Most
Filling of Bladder
• Parasympathetic Sympathetic
S2, S3, S4(nerve erigentes) Few
Emptying of Bladder
• Somatic
Pudendal nerve
Voluntary contraction of micturition

5. Sensory(Peripheral Afferent)
Pelvic nerve afferents consist of the following 2 fibers:
• Myelinated A-delta fibers:
* Mediating normal micturition sensitive to gradual distention of the urinary
bladder
• Unmyelinated C-fibers:
*Under normal conditions: do not respond to bladder distention.
*Various pathological conditions including
• SCI: Chemoreceptors and mechano-sensitive nociceptors from the bladder and urethra
become hyperactive and can cause hyper-reflexic bladder and urinary incontinence.

7. Peripheral efferent innervation(motor)
• Sympathetic pathways:-
• Originate from the T11-L2
• Travel through inferior-mesenteric / hypogastric plexus and
hypogastric nerve to reach the Pelvic plexus
• Inhibit the bladder body and excite the bladder base and
proximal urethral sphincter
• Parasympathetic nerves:
• Emerge from the S2-4
• Pass via pelvic nerves to the pelvic plexus
• Excite the bladder and relax the urethral sphincter
• Sacral somatic pathways:
• Emerge from the S2-4 (Onuf’s nucleus)
• Form pudendal nerve
• Efferent fibres of which excite the distal striated urethral
sphincter causing its contraction.

8. REFLEXES
STORAGE REFLEXES
SYMPATHETIC STORAGE REFLEX SOMATIC STORAGE REFLEX
(Bladder afferent loop reflex) (Guarding reflex)

9. • SYMPATHETIC STORAGE REFLEX (Bladder afferent loop reflex)
Urine storage mechanism.
Reflex activation triggered by afferent activity induced by distention of
the urinary bladder.
-stimulating α1 adrenergic receptors in the urethral
smooth muscle: -> promotes closure of the urethral
outlet
-stimulating β3 adrenergic receptors in the detrusor
smooth muscle: -> inhibits neurally mediated
contractions of the bladder

10. • SOMATIC STORAGE REFLEX (Guarding reflex)
During normal urine storage this pathway is tonically
active.
-A more rapid somatic storage reflex: during sudden
unexpected increase in bladder pressure like
coughing , sneezing or straining, it becomes
dynamically active to contract the rhabdosphincter.
-Alterations in these mechanisms may develop in
neurogenic bladder dysfunction.
-Direct activation of these reflexes by electrical
stimulation of the sacral spinal nerve roots (sacral
neuromodulation) is proved to be clinically effective

12. • SOMATIC MICTURITION REFLEX -
(urethra to bladder reflex)
To aid normal unhindered voiding-
In response to urethral fluid flow,
sensory nerves in the wall of the
urethra send afferent inputs
through the pudendal nerve to
the sacral spinal cord.
This aids voiding by –
-initiating bladder contractions in
the quiescent bladder
-augmenting bladder
contractions already underway
-suppressing sphincter activity

17. Thank You