Neural Control of Pelvic Function 1 Flashcards

Describe the role of somatic (pudendal), sympathetic, and parasympathetic nerves in urination and defecation.

1
Q

What is the somatic innervation of pelvic function?

A
  • Pudendal nerve innervates striated muscles in pelvis:
    • external anal and urethral sphincters
    • bulbospongiosus
    • ischiocavernosus
    • transverse pineal
  • Pudendal plexus (S2-S4) innervates muscles of the pelvic diaphragm:
    • urogenital diaphragm
    • levator ani
    • coccygeus
    • pubococcygeus
    • circumvaginal muscles
    • Kegel muscles
    • orgasmic platform
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2
Q

What is the sympathetic innervation of pelvic function?

A
  • Hypogastric nerve (T11-L2)
    • preganglionic neruons use ACh
    • postganglionic neruons arise from pelvic plexus, use NE
  • Lumbar colonic nerve (from inferior mesenteric ganglion)
    • innervates colon
  • Caudal sympathetic chain
    • pelvic organs
    • especially vasculature
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3
Q

What is the parasympathetic innervation of pelvic function?

A
  • Pelvic nerve (S2-S4)
    • both pre- and postganglionic (arising from the pelvic plexus) use ACh
    • peptide co-transmitters also important
    • inhibitory neurotransmitter usually nitric oxide
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4
Q

Where do afferent nerves of the pelvis travel?

A
  • Pelvic and pudendal nerves - few in hypogastric nerve
  • Visceral afferents in the pelvic nerve transmit distension information from:
    • bladder
    • colon
    • pain from viscera
    • other visceral sensations
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5
Q

What are some important developmental considerations regarding sexual dimorphism in innervation of the pelvis?

A
  • External genitalia differentiate from common embryological origins with homologous innervation
  • Internal genitalia from Wolffian ducts and Mullerian ducts under hormonal control
  • Default phenotype is female, and some organs (bladder and colon) don’t show any significant dimorphism.
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6
Q

What are some functional consequences of sexual dimorphism when considering pelvic innervation?

A
  • Sexual dimorphism of the pelvic innervation related to differentation of organs
  • However, neural circuitry mediating pelvic function is very similar
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7
Q

Describ the coordination of somatic and autonomic nervous systems

A
  • Most pelvic functions require both somatic and ANS activity
  • Defecation, micturition, and sexual function are mutually inhibitory to each other
  • Coordination is mediated primarily by the spinal cord
  • Sympathetic and parasympathetic activity is also highly coordinated, primarily by the spinal cord
  • Sympathetic and parasympathetic may be antagonistic or synergistic
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8
Q

Describe the hierarchical control of the nervous system supplying the pelvis.

A
  • Mediated at several levels
    • enteric nervous system (for colon)
    • autonomic ganglia
    • spinal cord
    • brainstem
    • hypothalamus
    • higher centers
  • More complex functions are managed by higher levels
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9
Q

What are the parasympathetic, sympathetic, and somatic innervations involved in micturition?

A
  • Parasympathetic
    • goes to detrusor and bladder neck via pelvic nerve
    • postganglionic neurons in pelvic plexus and ganglia on bladder
    • postganglionic neurons use ACh
  • Sympathetic
    • to detruser and bladder neck via hypogastric nerve and sympathetic chain
    • postganglionic neurons in pelvic plexus and sympathetic chain
    • postganglionic neurons use NE
  • Somatic
    • to external urethral sphincter and other striated muscles via pudendal nerve
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10
Q

What is the role of the detrusor muscle in micturition?

A
  • Smooth muscle
  • Acts in two modes - storage and expulsion
  • Contracted by ACh (muscarinic)
  • Relaxed by NE (beta) and nitric oxide
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11
Q

What is the role of the bladder neck in micturition?

A
  • Smooth muscle
  • Acts to prevent leakage of urine
  • Relaxed by nitric oxide and ACh (muscarinic)
    • due to contraction of longitudinal urethral smooth muscle
  • Contracted by NE
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12
Q

What is the role of the external urethral sphincter in micturition?

A

has a resting tone due to pudendal nerve activity

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