Lecture 38

• Human Sexual Response
  
  • (Four stages)
    
    • Excitation – excitation increasing
      
    • Plateau stage – excitation leveling off
      
    • Orgasm
      
    • Resolution – female vs. male resolution
      

       
       

• Excitation
  
  • Happens in both male and female
    
    • Heart rate begins to rise
      
    • Blood pressure begins to rise
      
    • Voluntary muscle tensing occurs
      
    • Erection of the nipples
      
      • In females early erection of nipples due to smooth muscle contraction
        
      • In females late nipple erection is due to Vasocongestion
        
      • n male nipple erection is inconsistent, only occurs in approx 60% males, and in most not until plateau stage, 40% are vasoconstrictive
        
  • In male alone
    
    • Contraction of the dartos muscle (smooth muscle)
      
    • Vasocongestion of the scrotal skin in male, thickens and elevates the scrotal sack
      
    • Contraction of the cremaster in the male (skeletal muscle in the spermatochore), this is the start of the contraction and continues through the plateau stage, lifts testis towards body and rotates them
      
    • Vasocongestion of the penis – called the erection
      
    • Vasocongestion of the
      
      • Cavernosa - some diminished blood return - due to tissues pressing against walls
        
      • Spongiosum stay soft, because no diminished blood return
        
      • Both due to vasodilatation of arterioles plus diminished blood return due to swelling tissues
        
    • Now, erection of the penis is mainly elongation
      
  • In the female
    
    • the vagina lubricates, not due to any secretion by any glands but due to neurons releasing VIP (vasoactive intestinal peptide) which causes local cells to kick electrolytes out into vagina and then fluid follows due to transudation
      
      • Vaginal lubrication is one of early signs of excitation in female
        
      • Quantity not a good indicator of level of sexual arousal
        
    • Vasocongestion of the genital region in female
      
      • Outer lips of the vagina will flatten and move apart
        
      • Labia majora increase in size
        
      • Labia minora thicken and expand
        
      • Clitoris becomes erect, increases slightly in size, not always discernible in lab settings
        
      • Inner two thirds of the vagina will lengthen and expand
        
      • Uterus is going to increase in size and begin to elevate into the pelvic cavity
        
      • Vasocongestion of the areola starts (area around the nipple)
        
      • Vasocongestion of the breasts begins
        
      • Sexual flush follows (appears in 75% of females)
        
        • first appears in epigastric region and then spreads to the breasts
          
        • Never appears anywhere else
          
        • Cannot be seen under normal levels of illumination
          

           
           

• Plateau stage (also referred to as "dumb phase", because brain lacks blood)
  
  • In both male and female
    
    • respirations increase, but only towards end of plateau stage
      
    • Heart rate continues to rise
      
    • Blood pressure continues to rise
      
    • Involuntary muscle tensing starts
      
  • In the male
    
    • sexual flush appears in 25% of males (much smaller percentage than in females), appears in the epigastric and then spreads (but not to same extent as seen in female)
      
    • Testis will vasocongest, increasing in size
      
    • Elevation of the testis continues via cremaster muscle contraction
      
    • Erect penis increases in size, but mainly circumferentially and not in length
      
    • Calpers gland in the male will release secretion - Set to adjust the pH of the urethra - Will contain some semen
      
  • In females
    
    • sexual flush becomes very extensive (in some females but not all)
      
    • breasts continue to increase in size through the plateau stage
      
      • Areolas going to become engorged and you see what you think is a small nipple
        
    • Outer one third of vagina expands but not as much as inner two thirds and forms the orgasmic platform
      
    • Posterior two thirds have expanded into what is called the seminal basin
      
    • During the plateau stage the uterus will fully elevate into the false pelvis and tip back
      
    • The labia minora will turn bright red to burgundy in color
      

       
       

• Orgasm
  
  • Male and female
    
    • Respirations peak during orgasm as high as 40 (per min)
      
    • Heart rate peaks at approx 110-180 bpm
      
    • Blood pressure peaks (all values relative to "normal")
      
      • male
        
        • systolic goes up 40-100mmHg
          
        • diastolic up 20-50mmHg
          
      • female
        
        • systolic up 30-80mmHg
          
        • diastolic up 20-40mmHg
          
    • Sexual flush intensity will parallel orgasmic intensity
      
    • Only voluntary tensing occurs
      
  • Male orgasm (2 halves)
    
    • First half = emission
      
      • Bladder neck contracts making posterior urethra a closed chamber
        
      • Vas deferens contracts
        
      • Seminal vesicles and prostate gland begin series of contractions
        
      • Posterior urethra becomes filled with semen
        
    • Second half = ejaculation
      
      • Contractions of the prostate and seminal vesicles continues
        
      • Sphincter urethra will pop open and the bulbospongiosus and the ichiocavernosus plus other perineal muscles (muscles in area of perineum) undergo involuntary contractions - Entire smooth muscle of urethra will contact in pulsitial fashion
        
      • Pulsing sends semen out of the penis in spurts
        
  • Female orgasm
    
    • Orgasmic platform has a series of contractions at the same time the uterus has a series of contractions
      
    • Contractions in the uterus end in intrauterine pressure drops
      
    • The cervix shoots down into the seminal pool during pressure drops
      

     
     

• Resolution - return to the normal values
  
  • Rapid
    
    • in males and females
      
      • respiration, heart rate, blood pressure, back to normal, sexual flush disappears, genital vasocongestion can be prolonged in some males - prolonged erection after male has ejaculated
        
    • in the female
      
      • Areola and nipple size resolution will be rapid
        
  • Prolonged
    
    • in males and females
      
      • muscle tensing
        
    • In the male alone
      
      • nipple erection can be prolonged
        
      • in the male there are sweaty palms and soles of the feet (inconsistent finding)
        
    • in the female
      
      • breast size will be prolonged
        
      • uterus will slowly drop down into the cervix
        
      • cervix will drop down into seminal basin -
        
      • in the female you find widespread thin film of perspiration (not due to physical activity though)