Male Sexual Response Lecture Notes

Overview

• Male sexual response is divided into four phases, similar to females:
  1. Excitement
  2. Plateau
  3. Orgasm
  4. Resolution
• Understanding these phases is crucial for therapeutic treatments of sexual dysfunctions, particularly erectile dysfunction.

Key Terms

• Coitus/Copulation: Technical terms for the act of having sex. Also known as sexual reproduction or sexual intercourse.

Excitement Phase

• Parasympathetic Nervous System: Key player in the excitement phase.
• Erection Formation:
  • Vasocongestion occurs in erectile tissue (corpora cavernosum and spongiosum).
  • Transition from flaccid to erect state involves myotonia (increased muscle tension), increased heart rate, blood pressure, and respiratory rate.
  • Bulbourethral (Cowper's) glands secrete alkaline fluid to neutralize urethral acid.
  • Nitric oxide causes dilation of smooth muscles, leading to erection and penile blood flow.

Plateau Phase

• Occurs after erection, before orgasm/ejaculation.
• Characteristics:
  • Respiratory rate, heart rate, and blood pressure remain elevated.
  • Penis becomes increasingly erect and firm.
  • Duration varies from seconds to minutes depending on the individual.

Orgasm Phase

• Lasts about 3 to 15 seconds.
• Efferent Nerve Fibers: Trigger discharge of semen.
• Significant increase in heart rate, blood pressure, and respiratory rate.
• Nervous System Mnemonic: "Point and Shoot"
  • Parasympathetic for erection (point)
  • Sympathetic for ejaculation (shoot)

Ejaculatory Phase

• Emission:
  • Sympathetic activation causes peristalsis in reproductive ducts.
• Expulsion:
  • Muscular contractions expel semen into the female reproductive tract.
  • Internal urethral sphincter constricts to prevent urine mixing with semen.
• Age Impact: Muscle tone affects force of semen expulsion.

Resolution Phase

• Post-ejaculation return to baseline:
  • Heart rate, respiration, and blood pressure normalize.
  • Sympathetic constriction of internal pudendal artery causes erection to subside.

Refractory Period

• Period post-sex where males cannot achieve another erection or orgasm.
• Short in younger males (as brief as 10 minutes), longer in older males (up to hours).

Conclusion

• Questions and comments can be posted on the class discussion board or emailed.
• Encouragement for continued study.