Morning glory, or medically “nocturnal penile tumescence," is a familiar event. It occurs to all men; but the reasons vary according to the experts.
Erections are the consequence of the nervous and endocrine systems directing blood flow in the penis. On arousal, the brain activates the nerves that provide blood to the penis, causing an increase in blood flow, resulting in penis enlargement, or, a hard-on.
Conversely, this event can occur without brain stimulation. Which is to say, an erection may occur when not sexually aroused, for instance during sleep. It is considered a spontaneous effect.
Throughout REM sleep (dreaming phase of sleep), the sections of the brain that regulate penis function are deactivated. So, during this phase the non-sexual engorgement may occur.
There could be several instances during each sleeping period, and may occur during each sleep cycle for up to twenty (20) or thirty (30) minutes depending on the quality of the sleep cycle.
One theory is that a man’s full bladder stimulates the spinal cord nerves creating an erection or another is that it is the body’s way of assisting with internal body maintenance. Some scientific researches believe the increased blood flow, engorgement and deflation may be natural penile health.
It also may be the occurrence of non-sexual stimulation, such as rubbing against something or an actual REM response to dream stimulation “wet dream”.
The lack of a nocturnal erections may be an indication of disease affecting penile health. Such as diabetes impacting on blood supply to the penis or depression, which is psychological and not an indicator of disease or low testosterone.
Some believe that the random erections can act as an indicator of good health. Since good health is correlated with firm erections. So, that’s good news.
The real reason for you waking up with good ol’ morning glory are many and varied, but may be of a non-sexual nature. So, don’t be embarrassed, it’s natural and some men use the opportunity.