PHYSIOLOGY OF THE SEXUAL RESPONSE four phases Excitation: Vasocongestion: pelvic area receives more blood in general, in particular to genitals. Males: penile erection scrotal sac thickens, elevates

PHYSIOLOGY OF THE SEXUAL RESPONSE Excitation (Cont’d) Females: vaginal lubrication glans clitoris enlarges (similar to penile erection) nipples erect (myotonia: muscle contraction) breasts enlarge (vasocongestion inner lips of vulva swell and open, change in colour (darker) upper 2/3rds of vagina balloons cervix and uterus stand up: tenting effect angle of cervical opening more receptive to sperm

PHYSIOLOGY OF THE SEXUAL RESPONSE Excitation (Cont’d) Both Sexes: sex flush (can happen later) heart rate, respiration rate gradually increase generalized myotonia

PHYSIOLOGY OF THE SEXUAL RESPONSE Plateau: Both males and females continue vasocongestion to max Heart rate, respiration rate and blood pressure continue to increase Copious perspiration Increased myotonia

PHYSIOLOGY OF THE SEXUAL RESPONSE Plateau (Cont’d) Females: orgasmic platform: outer third of vagina thickens, swells: condition sine qua non: without it, no orgasm tenting complete clitoris erect

PHYSIOLOGY OF THE SEXUAL RESPONSE Plateau (Cont’d) Males: Cowper’s glands secrete fluid through tip of penis. WARNING: may contain live sperm! scrotum even higher and testicles bigger

PHYSIOLOGY OF THE SEXUAL RESPONSE Orgasmic: Males: Two stages: contraction of seminal vesicles, vas and prostate contraction of urethra and penis: ejaculation

PHYSIOLOGY OF THE SEXUAL RESPONSE Orgasmic: Females: contractions of orgasmic platform contractions of uterus several orgasms possible if stimulation continues oxytocin

PHYSIOLOGY OF THE SEXUAL RESPONSE Orgasmic: Both: very high heart rate, blood pressure and breathing intense myotonia

PHYSIOLOGY OF THE SEXUAL RESPONSE Health Benefits Associated With Orgasm General Health An orgasm at least once or twice per week appears to strength the immune system’s ability to resist flu and other viruses Pain Relief Some women find that an orgasm’s release of hormones and muscle contractions help relieve the pain of menstrual cramps and raise pain tolerance in general.

PHYSIOLOGY OF THE SEXUAL RESPONSE Health Benefits Associated With Orgasm (Cont’d) Lower Cancer Rate Men who have more than five ejaculations per week during their 20s have a significantly lower rate of prostate cancer later in life Mood Enhancement Orgasms increase estrogen and endorphins, which tend to improve mood and ward off depression in women

PHYSIOLOGY OF THE SEXUAL RESPONSE Health Benefits Associated With Orgasm Greater Feelings of Intimacy The hormone oxytocin, which may play a role in feelings of love and intimacy, increases fivefold at orgasm Better Sleep The neurotransmitter dopamine, released during orgasm, triggers a stress-reducing, sleep-inducing response that may last up to two hours

PHYSIOLOGY OF THE SEXUAL RESPONSE Emotional Changes During Orgasm: Based on EEG, MRI and PET scans done in the lab while subjects having an orgasm. General emotional response: coded in limbic association area, especially prefrontal cortex and cingulate gyrus. Pleasure: coded in basal forebrain, especially ventral tegmental area and its dopaminergic stimulation of the reward centres of the septal nuclei and the nucleus accumbens. Euphoria: probably by assymetric cortical activation The proportion and intensity of each varies with each orgasm. So: orgasms differ

PHYSIOLOGY OF THE SEXUAL RESPONSE Resolution: Return to normal, muscles relax, breathing etc. back to normal, blood back to circulation from genitals. Males refractory period EACH PHASE MUST BE FULLY COMPLETED IN ORDER TO REACH THE NEXT ONE

PHYSIOLOGY OF THE SEXUAL RESPONSE Each phase shows age changes. Excitation: Men: fastest 16-20 years, then slow decline Middle Age: very noticeable, need direct stimulation Old Age: need lots of direct stimulation Women: slower in teens, early 20s faster 30’s on Plateau: capacity for longer with age same, but never a big problem

PHYSIOLOGY OF THE SEXUAL RESPONSE Orgasmic: Men: intensity lessens from mid- to late 20s Middle Age: really noticeable ejaculate less volume, less forceful Resolution: Refractory period increases

PHYSIOLOGY OF THE SEXUAL RESPONSE Resolution: Men: longer refractory periods, 24 hrs. midlife, longer in old age. Women: no refractory periods ever.

20 30 40 50 60 70 80 Females Intensity of Response Males Age

NEUROPHYSIOLOGY OF THE SEXUAL RESPONSE Neural and hormonal involvement in sexual responses: Parasympathetic: arousal Sympathetic: orgasm Spinal reflexes: erection and ejaculation

NEUROPHYSIOLOGY OF THE SEXUAL RESPONSE Erection: sacral cord responds to stimulation sends message via parasympathetic to relax penile arteries: more blood flows to penis Also, message to brain awareness (not if spine severed above sacrum)

NEUROPHYSIOLOGY OF THE SEXUAL RESPONSE Ejaculation: higher in spinal cord message to sympathetic that causes muscle contractions Also, message to brain Awareness possibility of control

PHYSIOLOGY OF THE SEXUAL RESPONSE Women’s Neural Mechanisms: Not yet well known .