Updated: 6/9/2021

Male Sexual Response

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  • Overview
    • Male sexual response
      • controlled by the parasympathetic and sympathetic divisions of the autonomic nervous system (ANS)
        • erection ("point") is under control of parasympathetic ANS
        • emission ("shoot") is under control of sympathetic ANS
      • divided into 4 phases:
        1. excitement
        2. plateau
        3. orgasm
        4. resolution
  • Excitement and Plateau
    • Erection
      • parasympathetic division of autonomic nervous system control (pelvic nerve)
      • NO → (+) guanylyl cyclase → ↑ cGMP → smooth muscle relaxation and vasodilation
        • pro-erectile (tumescence) mechanism
      • cGMP-specific phosphodiesterase breaks down cGMP and limits vasodilation
        • cGMP-specific phosphodiesterase inhibitors treat erectile dysfunction
        • sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis)
  • Orgasm
    • Emission
      • sympathetic division of autonomic nervous system control (hypogastric nerve)
      • movement of ejaculate into prostatic urethra
        • facilitation by peristaltic contractions of vas deferens, seminal vesicles, and prostatic smooth muscles
    • Ejaculation
      • somatic nervous system control (pudendal nerve)
      • movement of ejaculate through urethra and out of penis
        • facilitation by rhythmic contractions of perineal muscles
          • includes ischiocavernosus and bulbospongiosus muscles of penis
    • Seminal fluid
      • seminal vesicle secretions
        • 60% seminal fluid volume
        • fructose, ascorbic acid, prostaglandins, phosphorylcholine, and flavins
          • fructose nourishes spermatozoa
          • prostaglandins induce peristaltic contractions in uterus and fallopian tubes to propel sperm up female reproductive tract
      • prostate secretions
        • 30% seminal fluid volume
        • prostatic acid phosphatase (PAP), prostatic-specific antigen (PSA), fibrinolysin, citric acid, zinc, and phospholipids
          • fibrinolysin liquefies seminal fluid
      • spermatozoa (sperm)
        • 10% seminal fluid volume
  • Resolution
    • Sympathetic division of autonomic nervous system control (hypogastric nerve)
    • NE→ ↑ [Ca2+]in → smooth muscle contraction and vasoconstriction
      • anti-erectile or pro-flaccidity (detumescence) mechanism

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