Waking up with an erection is a curious but often uncomfortable phenomenon that much of the world’s population has to deal with quite regularly. What is the scientific explanation behind this “Morning Power”?
Nocturnal penile tumescence (NPT), using the correct terminology, refers to spontaneous erections that occur during sleep or when waking up. All men, without erectile dysfunction, normally have these erections around three to five times during sleep.
NPT actually begins in the womb (yes, seriously, in the womb!) and continues throughout life. Women also experience arousal in their clitoris during sleep, as is also the case in many non-human mammals.
Although some different theories have been proposed in recent years to explain NPT, its cause remains 100% uncertain. As in clitoral erections, they are associated with REM sleep (the rapid eye movement stage of sleep).
Three of these theories take into account several factors:
1. Norepinephrine neurotransmitters
One idea is that during REM sleep, neurons that release the norepinephrine neurotransmitter located in an area of the protrusion (part of the brainstem) called the locus coeruleus are deactivated. These cells are believed to be associated with the inhibitory tone of the penis. So when their activity is reduced during REM sleep, these related testosterone excitatory tones can result in an erection.
2. Release of nitric oxide:
Other sources have also suggested that such awakenings are triggered by the release of nitric oxide, released by cells lining the inside of blood vessels present in the smooth muscle, causing it to relax. This also causes blood vessels to dilate, therefore increasing blood flow to the penis.
So we have talked about “how”, but what about “why”? One idea is that these sleep exercises actually contribute to a kind of “scheduled maintenance”. Erections make the erectile tissue (corpora cavernosa) swell, thereby oxygenating the tissue. This oxygenation maintains its good condition and helps prevent cavernous fibrosis, a condition that can ultimately lead to erectile dysfunction.
3. Urinary continence:
Another interesting theory although, as we will see, probably mistaken, is that these nocturnal erections prevent bedwetting in men.
There are two main types of erections:
Psychogenic: this begins with stimulating thoughts or images bringing on an erection through the nerve signals.
“Reflex”: This is an involuntary process occurring without erotic thoughts and believed to be triggered by a full bladder. Nerves controlling these reflex erections are found in the sacral nerves in the spinal cord that are also activated by a full bladder. While this may sound plausible, it seems unlikely since our body has many other methods to prevent bedwetting. Moreover, it would not make sense as it also affects women.
“It seems that the most likely explanation is that these nocturnal “joys” may really help keep the machinery oiled and healthy.”