Neural Control of Pelvic Function 1 Flashcards
Describe the role of somatic (pudendal), sympathetic, and parasympathetic nerves in urination and defecation.
What is the somatic innervation of pelvic function?
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Pudendal nerve innervates striated muscles in pelvis:
- external anal and urethral sphincters
- bulbospongiosus
- ischiocavernosus
- transverse pineal
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Pudendal plexus (S2-S4) innervates muscles of the pelvic diaphragm:
- urogenital diaphragm
- levator ani
- coccygeus
- pubococcygeus
- circumvaginal muscles
- Kegel muscles
- orgasmic platform
What is the sympathetic innervation of pelvic function?
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Hypogastric nerve (T11-L2)
- preganglionic neruons use ACh
- postganglionic neruons arise from pelvic plexus, use NE
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Lumbar colonic nerve (from inferior mesenteric ganglion)
- innervates colon
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Caudal sympathetic chain
- pelvic organs
- especially vasculature
What is the parasympathetic innervation of pelvic function?
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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
Where do afferent nerves of the pelvis travel?
- 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
What are some important developmental considerations regarding sexual dimorphism in innervation of the pelvis?
- 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.
What are some functional consequences of sexual dimorphism when considering pelvic innervation?
- Sexual dimorphism of the pelvic innervation related to differentation of organs
- However, neural circuitry mediating pelvic function is very similar
Describ the coordination of somatic and autonomic nervous systems
- 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
Describe the hierarchical control of the nervous system supplying the pelvis.
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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
What are the parasympathetic, sympathetic, and somatic innervations involved in micturition?
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Parasympathetic
- goes to detrusor and bladder neck via pelvic nerve
- postganglionic neurons in pelvic plexus and ganglia on bladder
- postganglionic neurons use ACh
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Sympathetic
- to detruser and bladder neck via hypogastric nerve and sympathetic chain
- postganglionic neurons in pelvic plexus and sympathetic chain
- postganglionic neurons use NE
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Somatic
- to external urethral sphincter and other striated muscles via pudendal nerve
What is the role of the detrusor muscle in micturition?
- Smooth muscle
- Acts in two modes - storage and expulsion
- Contracted by ACh (muscarinic)
- Relaxed by NE (beta) and nitric oxide
What is the role of the bladder neck in micturition?
- 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
What is the role of the external urethral sphincter in micturition?
has a resting tone due to pudendal nerve activity