Erection Explained: The Proper Definition

Whether you have a penis or not, you might be confused about erections. Like any other body part, you need to know many things to understand an erection fully.

In this article, we’ll cover why and how an erection happens, how they feel, how to make an erection stop, and more.

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What is an erection?

Oxford languages¹ describe an erection as “an enlarged and rigid state of the penis, typically in sexual excitement.” While this definition might describe an erection in a technical sense, let’s dive deeper into what it actually means.

The penis has two major muscles. Centrally, you have the corpus spongiosum. Laterally, you have two corpora cavernosa which contain the erectile tissue.

An erection can be caused by more than just physical touch. Erections can also be driven by emotions, including sexual or arousing thoughts. 

When an erection is caused by physical touch, this is called the reflex response through activating the parasympathetic nervous system (PNS)². When it’s caused by emotions, this is the psychogenic response³ through certain pathways in the brain, including the limbic pathway, which is involved in emotional response. 

What happens when sexual stimulation occurs?

When sexual stimulation occurs, this activates the PNS⁴ to release a series of molecules to relax the erectile tissue. This effect allows more blood to enter the arteries of the penis. The result is an erection.

Of course, when an erection occurs during sexual stimulation, this is most likely with a sexual partner. To reach ejaculation, maintaining an erection is crucial.

An important step that maintains erections is to decrease the rate at which the blood leaves the penis. When the arteries push against the veins and compress them, this creates a barrier to achieving this.

Why does an erection happen?

To understand how an erection happens, it’s good to note that nerves play a crucial part in bringing a flaccid penis to an erect one.

Erectile function is controlled by a branch of the nervous system called the autonomic nervous system⁵. Within this system, the sympathetic nervous system inhibits erections, and the parasympathetic nervous system facilitates erections.

You can have three types of erections.

Nocturnal erection

As the name suggests, nocturnal erections occur during the night when sleeping. Research⁶ states that men of all ages can experience nocturnal erections during the rapid eye movement (REM) sleep stage.

Key factors related to frequent nocturnal erections include testosterone and androgens⁷.

It is thought that nocturnal erections occur to increase tissue oxygenation during sleep with engorgement of the corpora cavernosa.

While nocturnal erections are normal and are nothing to be ashamed of, prolonged or painful nocturnal erections can lead to disrupted sleep.

Psychogenic erection

A psychogenic erection occurs through thoughts, fantasies, and emotions. They usually occur during or after receiving visual, auditory, mental, or emotional stimulation.

Several nerves control the development and maintenance of a psychogenic erection. These include descending nerve pathways from the brain that transmits messages from the brain down the spinal cord.

Once they reach the sacral erection center near the bottom end of the spinal cord, the nerve signals are then transmitted to the pelvic plexus — also known as a collection of nerve fibers. Afterward, they travel through the cavernous nerve activating the erectile tissue of the penis.

Reflexogenic erection

Reflexogenic erections⁸ occur in response to direct touch or physical contact. This can include direct contact with the penis or a surrounding erogenous zone.

Unlike psychogenic erections, reflexogenic erections don’t involve arousing thoughts or emotions. Rather, they are controlled by the nerves in the lowest part of the spinal cord with the parasympathetic pathway.

A reflexogenic erection occurs when sensory receptors in and around the skin of a penis are activated by touch. When this happens, sensory information is sent through nerves to the sacral erection center in the spinal cord. Yes, this is the same center that is activated for all types of erections.

While some of these messages go to the brain, others are sent via the cavernous nerve within the penis to induce an erection.

How does an erection happen?

Now that you know that an erection can occur during the night and from thoughts and physical touch, let’s recap how a general erection happens.

An erection occurs when feelings of arousal send nerve signals to the brain and the penis, which causes the muscles of the penis to relax and expand. In turn, this allows blood to pool into the corpus cavernosum or the spongy tissue in the shaft of the penis.

This is classified as an erection. To maintain an erection, the sheath surrounding the corpus cavernosum helps stop the blood from leaving the penis. This helps to keep the erection from disappearing too quickly, especially during a sexual encounter. 

An erection can reduce in size and dissipate once ejaculation occurs or, in the case of a spontaneous erection, once the stimulus is reduced. This can happen when the muscles of the penis contract, stopping blood from flowing into the penis and opening the channels for blood to leave the penis.

Who gets erections?

Anyone with a penis can get an erection. This includes biological men and trans men of all ages.

However, the type of erection can vary. Erections can start as early as when the boy is an infant. However, a parent may not notice until they reach toddler age. This is normal and a good sign that their penis is “working properly.”

These erections are not sexual in nature.

Once the boy enters puberty — generally around ages 9–15⁹, although they can also occur earlier or later — erections in response to sexual thoughts and stimuli alongside “wet dreams” can be more common.

Wet dreams are a slang term under the broader term nocturnal emissions¹⁰. This is when a male has a nocturnal erection that leads to ejaculation. This is a normal part of sexual development for the teen as they begin to grow and develop physically, emotionally, and sexually.

How do they feel?

How an erection feels can depend on what type of erection it is. Most describe erections as sensitive and pleasurable, especially in response to sexual stimuli or during sexual encounters.

However, if the erection is unwanted or random, it can start to feel uncomfortable. Associated with unwanted erections and erectile dysfunction are feelings of shame, embarrassment, or anxiety.

If the erection is prolonged due to a medical condition or misuse of medications like Viagra, it can even be prolonged and painful.

Is discharge normal?

Normal penis discharge includes pre-ejaculate and ejaculate that occur in response to sexual stimuli or sexual activity. Other discharges may be indicative of an STD or another health condition.


Ejaculation occurs in response to sex or masturbation. While ejaculation and orgasm often go hand-in-hand, they are two separate processes meaning orgasm can also occur without ejaculation and vice versa.

Ejaculation is essential for procreation in all species. Ejaculate¹¹ contains sperm cells needed to fertilize an egg, alongside other bodily fluids that help neutralize the acidity of vaginas and nourish sperm.

Other discharge

Alongside regular ejaculation that occurs at the end of a sexual encounter, pre-ejaculate can also be released from an erection. This is often at the beginning of sexual arousal.

The pre-ejaculate’s role is to “flush out” the urethra in preparation for sexual activity and ejaculation.

If you have discharge that is more brown, red, or yellow in color, smells bad, or feels painful, it’s always good to check up with your doctor to make sure it’s not a sexually transmitted disease or infection.

How do you make an erection stop?

There are a number of ways to make an erection stops. These can range from meditation, deep breathing, and distraction techniques to light exercise and cold showers. Generally, an erection will subside after the sexual encounter or once your brain stops focusing on sexual thoughts.

This is often why some experts recommend distraction techniques to stop an erection. 

If you’ve taken medication like Viagra leading to a prolonged or painful erection, get help as soon as possible.

How frequently should you get an erection?

With such a broad range of sexual desires and drives in the world, it makes sense that there’s no “normal” frequency of erections you should aim to get.

However, those with penises can get an average of 3–5 nocturnal erections and 10–15 during a day of varying durations.

What does it mean if you can't get an erection?

Erectile dysfunction

Erectile dysfunction¹² (ED) occurs when a male cannot keep an erection firm enough to satisfy sexual intercourse with a partner.

ED can result in mental stress and anxiety, which can have a negative effect on a person’s love life, relationships, and self-esteem.

ED is more common than most people might think. This common disorder affects up to 30 million¹³ men in the US alone. While someone with ED can feel isolated, there are various ways to get help.

Numerous factors can cause erectile dysfunction, and discovering why you are experiencing problems can sometimes be frustrating and difficult.

Generally, young men experience ED due to psychological stress or a side effect of a medication they are on. Other factors contributing to ED for men of all ages include obesity¹⁴, excess alcohol consumption¹⁵, and neurogenic disorders¹⁶. The prevalence of ED only increases with age. In fact, after the age of 60¹⁷, ED rates are seen to increase independently of other contributing health conditions like hypertension and diabetes.


ED is often diagnosed clinically in primary care settings. Diagnosis can include:

Individual and family history

Your individual and genetic history is an essential part of the consultation between you and your doctor. Certain clues in your history can direct the doctor toward making a diagnosis.

Physical examination

This examination will include the chest, genital areas, and distribution of body hair. Peripheral blood vessels will also be checked to rule out vasculogenic causes.


There are a wide variety of treatments for ED. Typically, first-line options include lifestyle changes, medication, therapy or counseling, and vacuum pumps. If the ED is advanced, these treatments can be unsuccessful.

In this case, surgical and vascular implants are another option.


Oral PDE5 inhibitors¹⁸ are commonly used to treat ED, including sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis). They act to increase blood flow to the penis.

Viagra is probably the most popular drug to treat ED and is often the first medication prescribed by a doctor. While it’s relatively safe to use, it can be dangerous when combined with other medications resulting in low blood pressure and heart attacks, which can be fatal.

For some, other forms of medications will be prescribed. While supplementary testosterone is another option, it has mixed results. One review¹⁹ found that improvement to erectile function took over six months to occur.

Talk therapy

If the ED is caused by stress, anxiety, or PTSD, talk therapy or counseling can be a great treatment option in addition to medication.

Counseling and psychotherapy²⁰ can help lower the stigma surrounding ED and help the person understand that this is a common condition triggered by various psychological factors.

Talk therapy can also be great for partners, especially if the ED affects their sex life. 

Vacuum pumps

Vacuum pumps are not as popular as medications since they’re more invasive. Pumps are placed over the penis, creating pressure that forces blood into the penis to produce an erection.

Often, an additional physical constriction at the base of the penis and negative pressure is needed to prevent blood from leaving.

While this method has generally been taken over by medications as the preferred treatment for ED, vacuum pumps have shown promising results in preserving erectile function.


There are some surgical options available for ED.


Penis implants can be shaped or inflatable. One study²¹ reported a 90% satisfactory response.

Vascular surgery

Vascular surgery can be considered if the blood vessels to the penis are not working. One study²² reported a 12% satisfactory response.

When should I see a doctor?

While erections are a normal part of life for those with a penis, you may want to seek additional advice from a health professional if you’re worried about the health of your penis.

Erectile dysfunction is relatively common in men of all ages, and you shouldn’t feel ashamed of getting help. You should visit your doctor when you suspect you might have ED or you know you have ED, and it is negatively affecting your social and sexual health and overall quality of life.

If needed, they may refer you to a specialist doctor to get additional treatment options. 

You should also consult your doctor before stopping any medications that could cause erectile dysfunction or if you are experiencing any side effects to medications.

As explained earlier, you should also see a doctor if you’re having prolonged erections or an abnormal amount of spontaneous erections, as this can be indicative of a health condition.

The lowdown

Erections are normal and indicative of a healthy penis. However, if the duration, frequency, and discharge of your erections are abnormal, it’s important to see your doctor.

There are numerous options to treat abnormal erections or ED, including therapy, medications, and surgery.

  1. Oxford languages and google | Oxford Languages

  2. Neural control and physiology of sexual function: Effect of spinal cord injury (2017)

  3. Impaired prefrontal-amygdala pathway, self-reported emotion, and erection in psychogenic erectile dysfunction patients with normal nocturnal erection (2018)

  4. Neuroanatomy, parasympathetic nervous system (2022)

  5. Neuroanatomy and neurophysiology related to sexual dysfunction in male neurogenic patients with lesions to the spinal cord or peripheral nerves (2010)

  6. Nocturnal penile erections: A retrospective study of the role of RigiScan in predicting the response to sildenafil in erectile dysfunction patients (2018)

  7. Testosterone and sleep-related erections: an overview* (2005)

  8. Physiology of penile erection and pathophysiology of erectile dysfunction (2006)

  9. The role of puberty in the developing adolescent brain (2010)

  10. Nocturnal emissions: A comparative study of male experiences and reactions (1982)

  11. Semen physiology | News Medical Life Sciences

  12. Erectile dysfunction (ED) | NIH: National Institute of Diabetes and Digestive and Kidney Diseases

  13. Definition & facts for erectile dysfunction | NIH: National Institute of Diabetes and Digestive and Kidney Diseases

  14. Prevalence of and risk factors for erectile dysfunction in young nondiabetic obese men: results from a regional study (2020)

  15. A meta-analysis of erectile dysfunction and alcohol consumption (2021)

  16. Organic causes of erectile dysfunction in men under 40 (2014)

  17. Erectile dysfunction in the elderly: An old widespread issue with novel treatment perspectives (2014)

  18. Which drug for erectile dysfunction? | Harvard Health Publishing

  19. Erectile dysfunction (2017)

  20. Psychotherapy for erectile dysfunction: now more relevant than ever (2004)

  21. Penile implants: a look into the future (2017)

  22. Implants, mechanical devices, and vascular surgery for erectile dysfunction (2010)

Other sources:

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