How the Central Nervous System Controls Erection & Ejaculation

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  • 0:00 Central Nervous System
  • 0:44 Erection
  • 2:11 Ejaculation
  • 3:44 Lesson Summary
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Lesson Transcript
Instructor: Adrianne Baron

Adrianne has a master's degree in cancer biology and has taught high school and college biology.

In this lesson, we are going to look into how the central nervous system puts together the necessary series of events to cause an erection and subsequent ejaculation to occur.

Central Nervous System

Everything must happen in the designated sequence in order for it to occur just right. Now, we aren't talking about launching a rocket, which must also follow a designated sequence, but we are talking about sex. Didn't know sex required a specific sequence of events? Well it does. This is especially true for men.

The sequence of events in men is orchestrated by the central nervous system, which is the brain and spinal cord. I guess you can say that makes sense, since your brain tells every other part of your body what to do. Why wouldn't your brain tell your sex organs what to do as well? By sex organ, we are referring to the penis. Now that we know what the brain is controlling, let's talk about this sequence that it controls.


You should first recall two parts of the central nervous system. One is the parasympathetic, and the other is sympathetic. You may have heard about these two parts when you learned about the fight-or-flight response. The sympathetic gets the body ready to fight or get away, and the parasympathetic relaxes the body.

While sex can be very exciting, a man has to be relaxed in order for everything to go just right. This is the job of the parasympathetic central nervous system. The brain and spinal cord have a network of nerves at their disposable through which they can send and receive signals. The chemical nerve signals are called neurotransmitters. When a man receives visual, physical, or even imaginary sexual stimulation, this causes signals to be generated in the brain. The signals then act upon three of the nerves that branch off from the sacral region of the spinal cord.

The nerve endings in the region of the penis will then begin to release the erectile neurotransmitters, nitric oxide and acetylcholine. Both of these cause the walls of the blood vessels to relax, allowing for more blood flow to the penis. The penis becoming full of blood, causing the extension of the tissues of the penis is known as an erection. The continuous stimulation is necessary to keep the neurotransmitter levels up so that the penis will stay erected for sex.


It is now time for the finale! There is a sequence of events that make ejaculation happen as well. Ejaculation, or the expelling of semen from the penis, is controlled by both the parasympathetic and sympathetic nervous system. The two phases of ejaculation are emission and expulsion.

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