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  • It effects grown men, little boys and even happens to males still in utero.

  • You know, the ability to "pitch a tent" in the morning, without any actual camping skills.

  • Now that we got the one obligatory joke out of the way, we can get to the hard facts of nocturnal penile tumescence, otherwise known as "morning wood".

  • It turns out morning erections are part of the normal sleep cycle and occur multiple times throughout the night.

  • The mind and body go through stages of sleep, from non-REM stages, which gradually become deep sleep finally followed by REM or "Rapid Eye Movement" sleep which is actually fairly shallow sleep.

  • This cycle occurs between 4 or 5 times a night.

  • As you enter REM sleep, not only do dreams occur, but a few physiological changes take place as well.

  • Namely, your brain begins to shut off some neurotransmitters in an effort to regulate your body, and in some cases stop you from acting out your dreams.

  • One of these neurotranmitters, norepinephrine, happens to be involved with the control of erections.

  • Specifically it causes vasoconstriction of penis blood vessels, actively preventing an erection.

  • It is like a stop sign for blood flow. But as you enter REM sleep, norepinephrine decreases and testosterone related actions are now able to take place.

  • This leads to vasodilation, or increased blood flow to the blood vessels, ultimately causing an erection.

  • Why is this important?

  • Well, similar to muscle and other tissue, at night this extra blood increases oxygenation, serving as a system of repair and helping to maintain functionality.

  • But why do we often wake up to this pleasant surprise?

  • Well, we often wake up just out of REM sleep, and as a result see the remnants of this sleep stage.

  • There is also evidence that a full bladder can contribute to morning wood.

  • The increased baldder size for the night stimulates a region of the spinal cord which can cause a reflex erection.

  • The physiological benefit of this is to prevent you from urinating in your sleep.

  • But most men can attest to the difficulty proposed by this conundrum after waking in the morning.

  • Rise and shine.

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It effects grown men, little boys and even happens to males still in utero.

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