Ejaculation may feel like a glorious mess, as uncontrollable as an avalanche or a runaway train.
Heres how it works.
Sexual Feedback
Ejaculation is the endpoint of a process that begins with a touch.
Skin covering the shaft and glans of the penis is filled with nerve endings sensitive to pressure and vibration.
Stroking that skin sends signals to the brain that say sexytime!
More touching further increases sensitivity, in a positive feedback loop that can build to a show-stopping involuntary eruption.
Anddespite the tails, they cant yet swim for themselves.
Instead, smooth muscles in the walls of male reproductive organs contract in a coordinated wave.
Its base also swells slightly, forming a structure called the urethral bulb.
As semen fills the urethra, pressure starts to build in the bulb.
(The fact that the bladder closes up shop is also why urine doesnt spurt out at orgasm.)
With nowhere else to go, the semen inflates the urethral bulb like a water balloon.
The whole processcalled emissionhas taken about 3 seconds, and its been paired with a growing feeling of inevitability.
Now were ready for the big finish.
And once it starts, it cant be stopped.
A second surrounds the urethra proper.
When the right signal arrives, the pumping starts.
Sensory feedback from the pulsed contractions tie into (and may intensify) the brains orgasmic cascades.
Once thats done, at least for a while, all thats left is the mopping up.
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