Sexual Arousal & Ejaculation

SEXUAL AROUSAL & SEXUAL STIMULATION

Sexual arousal begins with the desire to engage sexually, followed by the penis becoming erect, and potentially culminating in the release of pre-ejaculation fluid and ejaculation of semen.  If we were to put steps in the process they would largely follow this pathway:

  • Libido/Sexual Desire

  • Sexual Arousal & Sexual Stimulation

  • Release of Pre-Ejaculate

  • Ejaculation of Semen & Orgasm

  • Refractory Period

 

Libido

 

Libido is the term to describe the desire to behave sexually.  Libido can vary from one man to the next and from one hour or even minute to the next in the same individual.  Men’s libidos typically tend to be higher than women’s.  In addition, men are able to move from a state of little interest in sex to a great desire for sex in a matter of a minute or less.

 

Libido is hormonally affected by testosterone and prolactin.  Higher testosterone levels tend to increase sexual desire.  Since men’s testosterone levels fluctuate throughout the day, their libido can likewise fluctuate.  In fact, testosterone levels tend to be highest in the early morning, and many men wake up with a high libido.  This results in some men desiring to engage in sexual activity first thing in the morning.  Prolactin on the other hand has a tendency to decrease sexual desire.  Prolactin is mainly release in men during and just after ejaculation.  Its release during this time is critical in causing an erection to subside and accounts for the decreased desire to immediately engage in sexual activity again.  However, the effects of this type of prolactin are short lived and men can have their libido rebound within minutes to an hour.  However, men that have prolactin secreting tumors and chronic high levels of prolactin or low testosterone may have issues with low libido.

 

Sexual Stimulation

 

Sexual arousal can occur either via mental or physical stimulation.  This stimulation is processed by the spinal cord rather than directly by the brain.  So in effect, sexual arousal in men can often be a reflex.  This explains why erections usually occur by reflex rather than being 100% controlled by an “on/off” switch in men. 

Mental stimulation (also called psychogenic stimulation) involves visual images, thoughts, emotions, smells, anticipation, or sexual motivation – these cues allow the central nervous system to send signals to the erectile centers in the spinal cord leading to the penis becoming erect. 

 

Physical stimulation (also called reflexogenic stimulation) also sends signals from nerves in the genitals, namely the penis and to a lesser extend the scrotum and then on to the pudendal nerve.  Activation of the pudendal nerve enhances an erection. 

 

Physical stimulation of the erect penis excites the dorsal penile nerve.  When the penis is erect, the nerves transmit sexually pleasurable sensations more easily and more intensely than when the penis is flaccid – this is due to the “tightness” of the penile skin allowing sexual sensations to proceed more effectively.  In anticipation for intercourse, the cremaster muscles in the scrotum contract pulling the testicles close to the body to get them out of the way during intercourse and to prevent testicular injury.  As the scrotum becomes more “tight” it also becomes more sensitive to stimulation (notably the back side of the scrotum) – this can enhance sexual stimulation by stimulating the posterior scrotal nerves.

 

Pre-Ejaculate Release

 

As the rigidity of the penis continues and sexual stimulation occurs, the bulbourethral glands may begin to produce a few drops of clear, slippery fluid called pre-ejaculate.  This fluid fills the urethra and in most men, a few drops are released from the tip of the penis.

EJACULATION

During sexual stimulation (both mental and physical), a few things begin occurring to prepare the male body to ejaculate.  First, the epididymis begins to press sperm through the vas deferens.   Some of the sexual glands like the seminal vesicles and prostate produce more fluid in anticipation of ejaculation.  In fact, nearly two-thirds of the fluid that composes semen is produced during sexual stimulation.  Continued sexual stimulation leads to a firing up of the nerves in the pelvic plexus which then communicates with the spinal ejaculation generator which is located in the small of the back between the 3rd and 5th lumbar vertebrae.  Once stimulation reaches a critical point, the spinal ejaculation generator begins firing commands to the reproductive glands and pelvic muscles to coordinate ejaculation.   

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Orgasm vs. Ejaculation

 

Ejaculation is almost always accompanied by orgasm.  However, ejaculation and orgasm are two separate events that happen to occur at the same time more than 99% of the time.  Orgasm is an intense feeling of physical and emotional pleasure.  In men, orgasm typically lasts for only a few seconds.  During this time, dopamine is released in the emotional centers of the brain by the VTA.  This dopamine then travels to the NAc or pleasure center of the brain to cause intense sensations of psychological and emotional pleasure.  At this same time, orgasm creates a heightened sense of physical pleasure and skeletal muscles contraction throughout the body. 

 

Ejaculation on the other hand is the process that occurs in the reproductive organs/glands to force semen out of the urethra.  Ejaculation is regulated by the part of the nervous system that is responsible for the “fight and flight” response.  Ejaculation occurs in two major steps – emission and expulsion.  When sexual stimulation reaches a critical point, orgasm usually begins almost immediately before emission. 

 

Emission

 

Emission basically involves the sexual glands emptying their contents into base of the penis to create semen. Some men describe this as when their “semen settles”.  The first step of emission involves the clamping shut of the neck of the bladder.  This is where the urethra exits the bladder before entering the prostate.  This prevents semen from moving backwards into the bladder rather than forward out of the penis.  After the urethra has snapped shut at the base of the bladder, the prostate contract pressing fluid into the urethra.  The epididymis at the rear of the testicle also contracts forcing sperm held further up in the ampulla to spill through the ejaculatory duct into the urethra as well.   These fluids collect in the portion of the urethra at the base of the penis.  This is then followed by contractions of the seminal vesicles.  The mixture of these sexual fluids is when semen is formed.  The contraction of the smooth muscles around these glands is affected not only by nerves but also by a release of oxytocin from the pituitary gland which causes smooth muscle contractions, especially in the prostate.  Once emission has occurred, expulsion is unstoppable – which is why many men describe this as the “point of no return”. 

Expulsion

 

Expulsion begins one to three seconds after emission has occurred.  The muscles in the root of the penis, (mostly the BS muscle but also the IC muscles) begin to contract rhythmically (about once a second).  The muscles of the prostate also contract forcing fluid forward and increasing pressure inside the urethra.  The muscles of the pelvic floor also contract rhythmically.  These contractions force the semen in the urethra at the base of the penis to move forward.  This expulsion occurs as muscular contractions move from the base of the penis in waves up the corpus spongiosum.  These waves occur multiple times and may vary from 8-12 times (sometimes more, sometimes less).  These waves expel semen from the penis quite forcefully which accounts for the way semen shoots out when released.  This forceful ejection helps the semen press further up the vagina to increase the chances of a sperm passing through the cervix into the female reproductive tract to fertilize an egg.  If muscle contractions are not as forceful (especially as men age), then semen can seep out in waves rather than being more forceful.


WHAT HAPPENING TO THE MALE BODY DURING EJACULATION

Hormones during ejaculation

 

When sexual stimulation has reached a critical point, oxytocin is released from the pituitary gland into the bloodstream thus causing the muscle contractions (especially in the reproductive glands).  These smooth muscle contractions in the reproductive glands assist with ejaculation of semen.  At the same time, the bonding effects of oxytocin cause the man to emotionally bond with his sexual partner.  For example, a man having intercourse with his wife would release oxytocin at sexual climax and emotional bonding to his wife while he’s ejaculating.  Serotonin is also released during ejaculation giving the man a sense of well-being.  The hormone prolactin is also released from the pituitary gland.  The combined influences of serotonin and prolactin cause an erection to subside and for sexual desire to decrease for a short period of time – this is called the refractory period.

Glands during ejaculation

 

During ejaculation a two-step process occurs in the glands.  The first step involves the prostate emptying its contents into the urethra. After a few seconds, the smooth muscles in the prostate will begin contracting rhythmically to expel semen and the seminal vesicles contract to release their contents.

 

Penis during ejaculation

During ejaculation, the bulbospongiosus (BS) muscle in the root of the penis begins to contract in a rhythmic fashion, forcing semen in waves up through the penis and out the urethra.  These contractions account for the pumping motion of the penis during ejaculation.  These contractions also press against the bulb of the spongiosum thus creating contractions that press the urethra in the base of the penis creating the forceful bursts of semen released from the urethra.  This explains why semen is releases in repeated waves rather than empting in a single stream like pre-ejaculate or urine.  Shortly after ejaculation occurs (for the next half minute or so), the BS and IC muscles of the penis can contract occasionally as a reflex causing the penis to “jerk” or “contract” randomly.  In addition, stimulation of the penis may no longer result in sexual stimulation of the penis.  Instead, physical stimulation of the penis can sometimes feel uncomfortable or tender. 

 

 

EJACULATION TIMING

The length of time it takes a man to ejaculate is called the “latency time”.  The latency time varies from one man to the next, and in all actuality changes in the same man from one sexual encounter to the next, especially as he ages.  These differences are largely due to different levels of psychological stimulation, length of foreplay, and pacing during intercourse, etc.  A study[i] performed in heterosexual men in a stable monogamous relationship found that on average, latency time of intercourse is approximately six minutes, with little difference between circumcised and non-circumcised men.  This was highly variable with one-seventh of men ejaculating in less than 3½  minutes compared to one-fourth of men taking 10 minutes or more to ejaculate.  In addition, latency time actually tends to decrease with age.   

 

As far as “what’s normal” a survey of sex therapists in Canada[ii] found that 3-13 minutes is often considered “normal” with 3-7 minutes being referred to as “adequate” and 7-13 minutes as “desirable”.  1-2 minutes was often considered to be “too short” and 13-30 minutes was often considered “too long” for many couples.  Latency times of less than 1 minute or longer than 30 minutes are often considered disorders.  In addition, it is possible for men to ejaculate with no sexual stimulation in circumstances that are not sexual whatsoever.  

REFRACTORY PERIOD

  

Within the first minute after ejaculation, the rigidity of the penis begins to subside and a period of time called the “refractory period” sets in.  During the refractory period sexual stimulation and therefore ejaculation is not possible for a period of time.  In addition, the penis may have excessive sensitivity leading to further physical stimulation being painful rather than pleasurable.  This is called the post-ejaculatory refractory period (PERT).  This refractory period usually increases in length as a man ages.  Reports indicate that it isn’t uncommon for young men in their early 20’s to have a refractory period of 15 minutes and men in their 70’s having a refractory period at 20 hours.[iii]  However, in clinical trials, the average refractory time in men during the child bearing years (late 20’s to early 40’s) is often between 30-60 minutes (but as much as three hours in some men).[iv] 

For some men (especially at younger ages), the refractory period may be almost non-existent, allowing them to not lose an erection and ejaculate a second time with continued stimulation.  Some men are termed multiorgasmic or able to experience multiple orgasms in a short period of time, but one study found that <10% of men in their 20’s and <7% of men in their 30’s are multiorgasmic.  In addition, men who forced multiple orgasms didn’t always ejaculate with the orgasm. 

This refractory period is thought to occur due the surges in oxytocin and prolactin from the pituitary gland.  Prolactin has the effect of lowering dopamine which is involved in sexual stimulation.  As dopamine levels fall, the interest in sex goes down significantly.  In addition, as dopamine levels fall, there is a sharp increase in serotonin – serotonin is sexually inhibiting.  Increasing serotonin is a main goal in the treatment of many types of depression, so it sometimes gets the nickname of the “happy hormone”.  Serotonin isn’t a hormone at all but does give people a sense of wellbeing and can cause drowsiness.  As oxytocin and serotonin surge, men have an intense feeling of well-being, they feel more bonded to their sexual partner/spouse, and becomes extremely relaxed – even to the point of falling asleep.  This explains why many men fall asleep or have a hard time staying awake after having sex.

 

WET DREAMS

(Nocturnal Emissions)

Wet dreams (nocturnal emissions) are spontaneous ejaculation that occurs when a man or young man is sleeping.  These are completely normal and described in detail in the Wet Dream section.

EJACULATORY DISORDERS

Ejaculatory disorders are the most common sexual disorders that effect men (more so than erectile dysfunction).  As the name suggests, ejaculatory disorders consist of issues men may face with ejaculation that is “not normal”.  

Disorders of ejaculation occur in many ways.  Some men may ejaculate much more quickly than they would like while others find it difficult to get enough sexual stimulation to ejaculate.  Others yet, may ejaculate spontaneously without any stimulation while other may experience orgasm but no semen is released.  

[i] Waldinger MD, Quinn P, Dilleen M, Mundayat R, Schweitzer DH, Boolell M (2005). "A multinational population survey of intravaginal ejaculation latency time". Journal of Sexual Medicine. 2 (4): 492–7

[ii] Corty, E. W.; Guardiani, J. M. (2008). "Canadian and American Sex Therapists' Perceptions of Normal and Abnormal Ejaculatory Latencies: How Long Should Intercourse Last?". The Journal of Sexual Medicine. 5 (5): 1251–1256.

[iii] https://greatist.com/play/male-refractory-period#prolactin (1/15/20)

[iv] Bhat GS, Association Between Post-Ejaculatory Refractory Time (PERT) and Premature Ejaculation (PE)., J Sex Med. 2019 Sep;16(9):1364-1370.