Erection & Ejaculation

• Erection


  A complex physiological process that involves the nervous, vascular, and endocrine systems, primarily regulated by the autonomic nervous system
• Ejaculation


  The process of expelling semen from the male reproductive tract, involving the coordination of the nervous and muscular systems
• Initiation of erection


  1. Sexual arousal begins with sensory stimuli

  2. Activation of parasympathetic nervous system

  3. Nitric oxide (NO) is released from nerve terminals and endothelial cells

  
• Role of nitric oxide (NO)

  • Activates guanylate cyclase in smooth muscle cells of the penile arteries and cavernous tissue
  • Guanylate cyclase converts guanosine triphosphate (GTP) to cyclic guanosine monophosphate (cGMP)
• Smooth muscle relaxation


  1. Increased cGMP levels lead to smooth muscle relaxation in the arteries and trabeculae of the erectile tissue

  2. Relaxation of smooth muscle allows increased blood flow into the cavernous spaces of the penis

  
• Maintenance of erection


  Phosphodiesterase type 5 (PDE5) degrades cGMP, and medications like sildenafil (Viagra) inhibit PDE5, thus maintaining elevated cGMP levels and prolonging erection

  
• Semen production


  Semen is produced in the testes and consists of sperm and seminal fluid from the prostate and seminal vesicles
• Ejaculation reflex


  1. Sexual stimulation leads to the activation of the sympathetic nervous system

  2. The ejaculation reflex is initiated by a spinal reflex at the level of the lumbar spinal cord
• Muscular contractions


  Muscular contractions occur in the vas deferens, seminal vesicles, and prostate, propelling semen into the urethra
• Urethral sphincters


  The external urethral sphincter contracts to prevent urine from mixing with semen during ejaculation
• Orgasm


  Ejaculation is often accompanied by orgasm, a pleasurable sensation mediated by the release of endorphins
• Understanding the intricate details of erection and ejaculation is crucial for both clinical and basic research, as dysfunction in these processes can lead to various sexual and reproductive health issues
• This knowledge forms the basis for the development of treatments for conditions like erectile dysfunction and infertility
• Role of the brain


  • Regulates sexual responses
  • Sends impulses to the erection center in the upper back
  • When connections between the brain and this center are inoperable, men fail to achieve erections solely in response to mental stimulation
  • Men require more sexual excitation to achieve full erection as they age
  • Brain can also stifle sexual response

  
• Role of the autonomic nervous system (ANS)


  • Division of the nervous system that regulates automatic bodily responses, such as an erection
  • Sympathetic branch largely controls ejaculation
  • Parasympathetic branch largely controls erection

  
• Erectile Dysfunction (ED)


  • Persistent inability to achieve or maintain an erection sufficient for satisfactory sexual performance
  • Causes include vascular issues, neurological disorders, hormonal imbalances, and psychological factors
  • Treatment may involve lifestyle modifications, medications like phosphodiesterase type 5 (PDE5) inhibitors, or surgical interventions
• Priapism


  • Prolonged and painful erection unrelated to sexual stimulation
  • Can be caused by blood disorders, medications, or underlying medical conditions
  • Emergency management involves draining excess blood from the penis and treating the underlying cause
• Peyronie's Disease


  • Development of fibrous scar tissue inside the penis, causing curvature during erection and pain
  • Can result from trauma or inflammation and may be associated with erectile dysfunction
  • Treatment options include medications, surgery, or in some cases, observation
• Premature Ejaculation


  • Persistent ejaculation with minimal sexual stimulation before or shortly after penetration
  • Often multifactorial, involving psychological, hormonal, and neurological factors
  • Behavioral therapy, topical anesthetics, or medications may be used for treatment