How exactly does our brain “direct” blood to a specific body part, e.g. for an erection?

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How exactly does our brain “direct” blood to a specific body part, e.g. for an erection?

In: Biology

It, for the most part, does not direct blood. It controls muscle contractions, which can clamp down vessels to slow blood flow to regions, such as reducing blood flow to one’s hands or feet when it’s cold.

Your circulatory system is just an interconnected series of pipes that goes around your body starting and ending at your heart. Like water pipes, you can increase or decrease the flow of these pipes. Your body directs flow by releasing certain signalling chemicals into the blood which makes the vessels (pipes) either expand/dilate/widen (vasodilation) or contract/constrict (vasoconstriction) to allow more or less blood through. Some of these act locally in a certain area, while others will act in a broad region of the body.

A penis is like a bouncing castle. Blood, or air is pumped in and blood, or air will passively leak out. During an erection, your body will increase the amount of blood going in by making the vessels expand in diameter. This means more blood goes in, while the same amount is going out. The net effect is a bouncier castle, or an erection.

For the most part, it comes from the release of chemicals that tell blood vessels to either dilate and increase blood flow, or constrict and reduce blood flow. There are various chemicals that do this, such as adrenaline, and different areas of the body are susceptible to them in different ways to give some targeted control. For an erection specifically, the arteries dilate and the veins constrict, increasing blood flow in and decreasing blood flow out.