Of course, some of you might take issue with what exactly I’m referring to when I use the term “brain.” Admittedly, it’s not a very big brain. In fact, if we go by comparison – the bigger the penis, the smaller the penile brain – since the brain in the penis is mainly composed of only two nerves (nerves are simply “wires” that are attached to cell bodies in your head brain through any number of “extension cords” [interneurons] that run down into your body). But hey, if a one millimeter worm can have a brain and a mind, why not a penis?
I’m not claiming Penis Brain is one of Einsteinian proportions. Einstein’s brain was roughly composed of 86 billion brain cells (neurons) with probably more than 100 trillion wires. And the two-wired brain in your penis probably works best in close collaboration with the brain in your head when it practices skillful Male Organ Management (MOM). (Interestingly, the brain in Einstein’s penis didn’t work at all well with the brain in his head: thinking there was little chance he would ever win – he agreed to give his wife, Mileva any future Nobel Prize money if she would grant him a divorce. One of his brains desperately wanted to be able to legally keep putting his penis in his cousin Elsa [whom he would later marry]. Makes you wonder who the real brains of the outfit was, doesn’t it?).
Two, Two, Two Nerves in One
To check to see if the two nerves in your penis – the dorsal nerve and the cavernous nerve – truly constitute a brain, first check to be sure that you actually have a penis. Now pretend you’re 19 years old and find pictures of attractive naked men or women and imagine having sex with them and see what happens. Remember, in reality, it’s just you alone in a room while your brain, your pictures, your Kisspeptin Hormones and your penis contingently communicate with one another. Brain networks love feedback loops and care little how they come together or what they come together concerning.
When you look at those naked pictures, messages from your brain cells travel along spinal cord nerves, then branch off and wind their way down to your penis. Chemicals called neurotransmitters are then released from the ends of the nerves in the penis. Physical stimulation of the penis of one sort or another can also cause penile nerve endings to release neurotransmitters.
Here’s MedScape describing how the brain in the penis gets busy doing its work in great detail. It can make for some very stimulating pillow talk:
Adrenergic nerve fibers and receptors are present in the cavernous trabeculae, and they surround the deep penile arteries. Noradrenaline is the major neurotransmitter controlling penile flaccidity and tumescence (erectilation). Sympathetic contraction is thought to be mediated by activation of postsynaptic alpha-adrenergic receptors and modulated by presynaptic alpha-adrenergic receptors. Acetylcholine is required for vascular smooth muscle relaxation, and cholinergic nerves have been demonstrated within the cavernosal smooth muscle and surrounding penile arteries.
Nitric oxide (NO) appears to be the principal neurotransmitter causing penile erection. Nonadrenergic, noncholinergic (NANC) neurons release NO. The release of NO increases the production of cyclic guanosine monophosphate (cGMP), which relaxes cavernosal smooth muscle. Other neurotransmitters, including vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP), prostaglandins, and other peptides, may also be involved in the erectile process. With relaxation of the smooth muscles in the trabeculae and the arterial wall, the following events occur in sequence, which leads to an erection:
1. Arterial inflow increases as a result of dilation of the arterioles and arteries. The sinusoids within the corpora cavernosa distend with blood. Subtunical venular plexuses are compressed between the tunica albuginea and the distended sinusoids, leading to decreased venous blood outflow.
2. The tunica albuginea is stretched to its capacity, compressing emissary veins and thus further decreasing venous outflow; as a result, intracavernous pressure increases and is further increased by contraction of the ischiocavernous and bulbospongiosus muscles, resulting in full rigidity.
3. The neurotransmitters released in the penis cause another chemical to be made – cyclic guanosine monophosphate (cGMP). This chemical causes the arteries in the penis to widen (dilate). This allows extra blood to flood into the penis. The rapid inflow of blood causes the penis to swell into an erection. The swollen inner part of the penis also presses on the veins nearer to the skin surface of the penis. These veins normally drain the penis of blood. So, the flow of blood out of the penis is also restricted, which enhances the erection.
Once you stop having sex, the level of cGMP falls, the blood flow to the penis returns to normal, and the penis gradually returns to the flaccid state.