This same mechanism can occur without the involvement of the brain, in an uncontrolled reflex action that is in the spinal cord. Several hormones are involved in influencing the brain’s response, such as testosterone (the main male hormone). The blood is trapped in the muscles of the penis, which makes the penis expand, resulting in an erection. When sexually aroused, a message starts in the brain, sending chemical messages to the nerves that supply the blood vessels of the penis, allowing blood to flow into the penis.

Penile erections occur in response to complex effects of the nervous system and endocrine system (the glands that secrete hormones into our system) on the blood vessels of the penis. It also has a female counterpart in the less frequently discussed nocturnal clitoral erection. Morning penile erections affect all males, even males in the womb and male children.

The morning penile erection, or as it is medically known, “nocturnal penile tumescence”, is not only an interesting physiological phenomenon, it can also tell us a lot about a patient’s sexual function.

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