Transcript Slide 1

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Parasympathetic afferent and efferent innervation of the bladder and urethra. The
preganglionic efferents originate in the sacral parasympathetic nucleus (SPN) of the
S2-S4 spinal cord. Preganglionics synapse in the pelvic plexus or within the bladder or
urethra. Neurons conveying afferent signal to the spinal cord dorsal horn have the
cell bodies located in the S2-S4 dorsal root ganglia (DRG). Both afferent and efferent
pathways are necessary for micturition and pain travel in the pelvic nerve.
•
Sympathetic afferent and efferent innervation of the bladder and urethra. The preganglionic efferents
originate in the interomediolateral cell column (IMLC) of the T11-L2 spinal cord. Preganglionics can
synapse on postganglionics in the sympathetic chain or pelvic plexus. Afferents have their cell bodies
located in the T11-L2 DRG. The hypogastric nerve conveys sympathetic afferents and efferents. Note
that the pelvic nerve also contains sympathetic fibers from the chain ganglia.
• Somatic afferent and efferent innervation of the bladder and urethra.
Efferent neurons reside in Onuf's nucleus (ON) of the S2-S4 spinal cord.
The efferents supply the innervation of the external urethral sphincter
through the pudendal nerve. Data indicate that the external urethral
sphincter is both autonomically and somatically innervated (see text).
Somatic afferents are conveyed to the dorsal horn of the spinal cord with
their cell bodies in S2-S4 DRG.
• A, Storage reflexes. During the storage of urine, distention of the bladder
produces low-level bladder afferent firing. Afferent firing in turn
stimulates the sympathetic outflow to the bladder outlet (base and
urethra) and pudendal outflow to the external urethral sphincter. These
responses occur by spinal reflex pathways and represent “guarding
reflexes,” which promote continence. Sympathetic firing also inhibits
detrusor muscle and transmission in bladder ganglia.
• B, Voiding reflexes. At the initiation of micturition, intense vesical afferent
activity activates the brainstem micturition center, which inhibits the
spinal guarding reflexes (sympathetic and pudendal outflow to the
urethra). The pontine micturition center also stimulates the
parasympathetic outflow to the bladder and internal sphincter smooth
muscle. Maintenance of the voiding reflex is through ascending afferent
input from the spinal cord, which may pass through the periaqueductal
gray matter (PAG) before reaching the pontine micturition center.
• The upper motor neuron refers to injuries that
are above the level of the anterior horn cell.
This results in a spastic type of paralysis.
Conversely, the lower motor neuron injury
refers to an injury at or below the anterior
horn cell that results in the flaccid type
paralysis. This is usually seen in nerve root
injuries or in the cauda equina syndrome