L19. GA - ANS Pelvis
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Questions and Answers

Which type of fibers are responsible for carrying stretch and pain information from the pelvic viscera to the spinal cord?

  • Efferent somatic fibers
  • Afferent somatic fibers
  • Afferent visceral fibers (correct)
  • Efferent sympathetic fibers
  • What is the primary function of autonomic efferent fibers in the pelvic viscera?

  • Modulate reflexes for defecation and micturition (correct)
  • Assist in voluntary muscle control
  • Regulate nutrient absorption
  • Transmit pain signals to the brain
  • Which of the following structures is NOT typically innervated by visceral efferent autonomic fibers?

  • Reproductive organs
  • Skeletal muscles (correct)
  • Bladder
  • Rectum
  • In terms of clinical application, why is knowledge of referred pain areas important?

    <p>It helps localize pathology of pelvic viscera.</p> Signup and view all the answers

    Which plexuses are involved in conveying autonomic fibers to the pelvic viscera?

    <p>Pelvic subsidiary plexuses</p> Signup and view all the answers

    Which component is primarily responsible for initiating the micturition reflex?

    <p>Parasympathetic nervous system</p> Signup and view all the answers

    What role do visceral afferent fibers play in the pelvic region?

    <p>Transmit sensory information about pelvic organ function</p> Signup and view all the answers

    How does Vesicare act in the treatment of Overactive Bladder (OAB)?

    <p>It blocks the effects of PANS acetylcholine at the M3 receptor.</p> Signup and view all the answers

    What role does Flomax play in managing Benign Prostatic Hypertrophy (BPH)?

    <p>It inhibits SANS norepinephrine's constricting effects on the internal urethral sphincter.</p> Signup and view all the answers

    Which of the following mechanisms prevents defecation until circumstances allow?

    <p>Tonic activity of the internal anal sphincter via SANS fibers.</p> Signup and view all the answers

    What initiates the activation of visceral afferent mechanoreceptors in the rectum?

    <p>Mass movement of feces pushing against rectal walls.</p> Signup and view all the answers

    What is the function of somatic efferent fibers carried by the pudendal nerve during the defecation reflex?

    <p>They maintain tonic stimulation of the external anal sphincter.</p> Signup and view all the answers

    What structures do the sympathetic nerves innervate in the male reproductive system?

    <p>Prostate and testes</p> Signup and view all the answers

    Which route do the preganglionic SANS fibers take when they travel through the sympathetic trunk?

    <p>They descend to the sacral sympathetic ganglia.</p> Signup and view all the answers

    What type of fibers synapse in the gonadal ganglia?

    <p>Preganglionic SANS fibers destined for the gonads</p> Signup and view all the answers

    What is the function of the inferior hypogastric plexus?

    <p>It gathers sympathetic nerves before they reach their targets.</p> Signup and view all the answers

    Where do most preganglionic SANS fibers destined for pelvic organs mainly synapse?

    <p>In the inferior hypogastric plexus</p> Signup and view all the answers

    Which nerve route do the preganglionic SANS fibers take to reach the inferior hypogastric plexus from the aortic plexus?

    <p>They utilize the hypogastric nerves.</p> Signup and view all the answers

    What is the primary role of the sympathetic trunk in the autonomic nervous system?

    <p>To serve as a conduit for preganglionic sympathetic fibers.</p> Signup and view all the answers

    What pathway is involved for the sympathetic innervation of the bladder?

    <p>Inferior hypogastric plexus pathway</p> Signup and view all the answers

    When do the preganglionic SANS fibers destined for the gonads synapse?

    <p>In the aortic plexus ganglia</p> Signup and view all the answers

    At what age do children typically master volitional control of micturition?

    <p>2-5 years</p> Signup and view all the answers

    Which condition describes involuntary urination that can occur at night?

    <p>Enuresis</p> Signup and view all the answers

    What describes the inability to void urine in certain settings, often associated with anxiety?

    <p>Paruresis</p> Signup and view all the answers

    What type of urinary incontinence occurs due to excessive involuntary muscle contractions?

    <p>Urge incontinence</p> Signup and view all the answers

    Which condition is associated with the narrowing of the urethra due to an enlarged prostate?

    <p>Benign Prostatic Hyperplasia (BPH)</p> Signup and view all the answers

    What type of incontinence is a result of neural circuitry dysregulation?

    <p>Neurogenic incontinence</p> Signup and view all the answers

    What mechanism can trigger urination in response to strong emotions?

    <p>Brainstem micturition center</p> Signup and view all the answers

    What is the main problem associated with detrusor-sphincter dysynergia?

    <p>Inefficient and incomplete voiding</p> Signup and view all the answers

    Which condition is caused by a narrowing or blockage of the urethra?

    <p>Overflow incontinence</p> Signup and view all the answers

    What is the effect of urinary tract infections (UTIs) on the bladder?

    <p>Promote feelings of urgency to void</p> Signup and view all the answers

    Which spinal levels do the preganglionic PANS fibers originate from?

    <p>S2-S4</p> Signup and view all the answers

    What is the function of pelvic splanchnic nerves?

    <p>Innervate the pelvic viscera for autonomic control</p> Signup and view all the answers

    How can pelvic splanchnics be distinguished from sacral splanchnics?

    <p>Pelvic splanchnics originate from S2-S4 ventral rami</p> Signup and view all the answers

    What is a key role of surgeons in relation to autonomic pathways during surgery?

    <p>To avoid disrupting autonomic pathways</p> Signup and view all the answers

    Which plexus is involved in pelvic organ innervation for both males and females?

    <p>Uterovaginal plexus</p> Signup and view all the answers

    What type of sensory information is conveyed by visceral afferents in pelvic plexuses?

    <p>Stretch and pain sensations from pelvic organs</p> Signup and view all the answers

    What are cavernous nerves responsible for innervating?

    <p>Erectile tissues in the perineum</p> Signup and view all the answers

    What is a significant consideration for anesthesiologists regarding pelvic organ nerve pathways?

    <p>Routes for visceral pain information transport</p> Signup and view all the answers

    Which plexuses are formed by PANS and SANS fibers in the pelvic region?

    <p>Inferior hypogastric plexus and subsidiary plexuses</p> Signup and view all the answers

    What is conveyed via the pudendal nerve in relation to pelvic sensory innervation?

    <p>Touch and pain sensations from the external genitalia</p> Signup and view all the answers

    Study Notes

    Autonomic Innervation of Pelvic Viscera

    • Summarize pelvic visceral efferent and afferent nerve fibers
    • Summarize the autonomic functional effects on pelvic viscera
    • Describe the gross anatomical organization of the pelvic visceral nerves
    • Explain sympathetic innervation of the pelvic viscera
    • Explain parasympathetic innervation of the pelvic viscera
    • Describe afferents from the pelvic viscera
    • Describe pelvic subsidiary plexuses

    Micturition Reflex

    • Describe the circuitry of the micturition reflex
    • Apply anatomical knowledge to discuss clinical problems affecting micturition

    Defecation Reflex

    • Describe the circuitry of the defecation reflex
    • Apply anatomical knowledge to discuss clinical problems affecting defecation

    Erection/Ejaculation Reflex

    • Describe the circuitry of the erection/ejaculation reflex
    • Apply anatomical knowledge to discuss clinical problems affecting erection/ejaculation

    Innervation of the Pelvic Viscera

    • Pelvic visceral efferent fibers innervate pelvic organs (rectum, bladder, reproductive organs) for reflexes (defecation, micturition, reproduction)
    • Visceral afferent fibers carry stretch and pain information to the spinal cord via the same nerve plexuses carrying autonomic fibers—this helps in localizing pelvic pathology
    • Parasympathetic (PANS) fibers for pelvic organs originate from spinal levels S2-S4 and travel in pelvic splanchnic nerves
    • Sympathetic (SANS) fibers for pelvic organs originate from spinal levels T10-L2 and travel in thoracic, lumbar, and sacral splanchnic nerves

    Autonomic Effects

    • Parasympathetic (PANS): vasodilation, contract bladder detrusor muscle, stimulate erectile tissues, increased colorectal peristalsis, relax internal urethral and anal sphincters
    • Sympathetic (SANS): vasoconstriction, contract internal urethral and anal sphincters, promotes sperm movement

    Gross Anatomical Organization

    • Sacral plexus sits on posterior wall of pelvic cavity, with ventral rami emerging from anterior sacral foramina
    • Pudendal nerve emerges and is critical for bladder, rectal, and reproductive reflexes
    • Sympathetic trunk also descends into the pelvic cavity, with 4 sacral ganglia converging at ganglion impar (pubococcygeus muscle area)

    Sympathetic Innervation

    • Preganglionic SANS axons from T10-L2 synapse in either aortic plexus (then inferior hypogastric plexus) or directly in sacral sympathetic ganglia
    • Aortic Plexus Route: travels through thoracic and lumbar splanchnic nerves, through superior hypogastric plexus, then utilizes left/right hypogastric nerves to reach the inferior hypogastric plexus, then synapse in ganglia within the inferior hypogastric plexus
    • Sympathetic Trunk Route: descends via sympathetic trunk to sacral sympathetic ganglia, then as sacral splanchnic nerves synapse with preganglionic fibers in the inferior hypogastric plexus
    • Gonadal Route: SANS fibers synapse in gonadal ganglia positioned around the abdominal aorta and along the vessels supplying the gonads

    Parasympathetic Innervation

    • Preganglionic PANS axons originate from S2-S4 spinal levels and travel via ventral rami of S2-S4 spinal nerves entering the pelvic cavity
    • Pelvic splanchnic nerves join the inferior hypogastric plexus and synapse in terminal PANS ganglia in pelvic viscera

    Pelvic Subsidiary Plexuses

    • Rectal plexus
    • Vesical plexus
    • Uterovaginal plexus
    • Prostatic plexus

    Afferents

    • Somatic afferents conveying touch and pain sensations from external genitalia travel through the pudendal nerve to S2-S4 spinal cord
    • Visceral afferents conveying stretch and pain from pelvic organs travel through the same plexuses carrying visceral efferent autonomic nerves
    • Pelvic pain line refers to visceral pain that travels superiorly to contact the peritoneum vs. subperitoneal pelvic cavity

    Micturition (Bladder control)

    • Filling: Stretch receptors in the bladder wall are quiet, but become active when walls are stretched
    • Micturition Centers: S2-S4 spinal cord; brainstem (pons) centers
    • Reflex Mechanism: PANS stimulation of the bladder's detrusor muscle relaxes the external urethral sphincter.
    • Control Mechanisms: SANS (T10-L2) maintains contraction of the internal urethral sphincter; SE pudendal nerve maintains contraction of the external urethral sphincter..

    Defecation

    • Stimulation: Stretch receptors in the rectum become active with fecal mass movement
    • Control: Visceral efferent SANS fibers maintain internal anal sphincter tone; somatic efferent fibers maintain external anal sphincter tone
    • Reflex Mechanism: Sufficient rectal volume triggers PANS stimulation of colon, relaxation of the internal anal sphincter, and contraction of the external anal sphincter.

    Erection/Ejaculation

    • Erection: PANS-mediated; spinal levels S2-S4; pelvic splanchnic and cavernous nerves stimulate NO release, vasodilation, and blood engorgement. Venous return decreases due to tunica albuginea expansion
    • Ejaculation: SANS-mediated, T11-L2; contraction of internal urethral sphincter, movement of fluid from vas deferens, prostate, and seminal vesicle. Relaxation of external urethral sphincter, contraction of muscles involved in semen expulsion.

    Clinical Problems

    • Urinary Incontinence: Stress, urge, overflow, neurogenic
    • Constipation: Normal transit, slow transit
    • Defecation Disorders: Impaired pelvic floor/anal sphincter function
    • Erectile Dysfunction

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    Description

    Test your knowledge on the autonomic nervous system and its role in the pelvic viscera. This quiz covers topics such as fiber types, functions, innervation, referred pain, and reflex actions. Assess your understanding of important concepts related to pelvic anatomy and physiology.

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