Leandie Buys Realtionship Therapist & Clinical Sexologist

How does an Erection Work?


The penis is made up of three spongy cylinders. It doesn’t contain any muscular tissue or bone as some people believe.

How does an erection happen?

Erections are considered neuro-vascular events. This means that the process of getting an erection involves complex interaction between veins, nerves and neurons.
Blood naturally flows into the penis through arteries (Helicine arteries) and out of the penis through veins (venules) just as it flows through the arms, legs and other parts of the body. In order for an erection to occur, the blood must be prevented from flowing out of the penis – causing the spongy cylinders to fill with blood, and the penis to become fully erect and hard.

3 Types of Erection

The process of an erection can begin in the brain, or directly from the penis itself.

  1. When it starts in the brain (psychogenic erection), triggers for the erection could be things like imagination, touch, hearing, smell etc… these triggers result in the brain sending a nerve impulse down the spinal chord to the penis to begin the erectile process. The neurotransmitters involved in this process are dopamine, serotonin and oxytocin (that will promote an erection) and noraderenalin (that will prevent an erection).
  2. An erection can also be the result of direct stimulation of the genital organs (reflexogenic erection).
  3. Erections can also occur at night (nocturnal erections). They occur mainly during rapid-eye movement (REM) sleep, the phase of sleep associated with dreaming.

The nitric oxide cycle

Following the stimulus (either originating in the brain or from direct stimulation of the penis), the body releases nitric oxide at the nerve endings of the penis. Nitric Oxide causes an increase in blood flow to the area – filling the spongy cylinders around the penis with blood.

How are erections inhibited?

  • Erections which start in the brain (psychogenic erections) may be hindered by emotional issues such as performance anxiety, marital discord, divorce or trauma such as the death of a spouse. Psychogenic causes are more common among younger men who suffer from erectile dysfunction.
  • Erections which start through direct stimulation of the penis (reflexogenic erections) may be hindered by organic risk factors such as medical conditions, structural abnormalities, medications, surgery, trauma and endocrine disorders. Older men are more like to have an organic cause for their erectile dysfunction.

The many possible risk factors for ED produce dysfunction by interfering with one or more of the following components of an erection:

  • The vascular component
  • The neurological component
  • The structural component of the penis

How do the following medical issues affect erections?

  • High blood pressure: This is when the pressure in the veins of the body is fairly high even when the heart is at rest. High blood pressure makes it more difficult for the blood to enter the penis. The elevated pressure in the arteries and veins also leads to friction between the blood and the vessel walls. This damages the delicate lining of the vessels – further inhibiting the erectile process.
  • Depression: Depression is often characterised by irregular levels of serotonin in the body. Serotonin is one of the neurotransmitters involved in erectile signalling in the brain, so irregular levels can cause issues with the erectile process.
  • Diabetes: Diabetic patients suffer from both micro and macro-vascular changes to the small arteries and veins that supply blood to and from the penis. Diabetic patients can also suffer from neuronal damage due to elevated glucose levels.  As erections are neurovascular events, these vascular and neuronal changes put diabetic patients at a particularly high risk of developing erectile dysfunction.
  • Cardiovascular Disease: Cardiovascular disease leads to the narrowing or blockage of blood vessels in the body. Constricted blood vessels around the heart increase a person’s risk of a heart attack or cardiovascular disease. Constricted blood vessels around the penis can also lead to erectile dysfunction.
  • Cholesterol: High cholesterol indicates a high risk factor for cardiovascular disease (which can lead to erectile dysfunction).

Diagnosing whether ED is the result of psychogenic or organic issues:

Patients will be sent for a full check-up at their GP to identify any physical (organic) issues that may be present. Tests include:

  • Full Blood Count
  • Urinalysis
  • Fasting blood glucose
  • Lipid profile (cholesterol)
  • Testosterone and prolactin
  • Thyroid function
  • PSA (prostate specific anigen) testing
  • Liver enzymes


Whether the diagnosis is psychogenic or organic, therapy is recommended. A patient suffering from ED due to an organic issue (such as high blood pressure) can treat the organic cause, but previous occurrences of ED may cause the patient to be anxious during sex which may lead to a secondary, psychogenic cause of ED.

Counselling is also recommended in order for couples to understand the causes of the ED, and to support each other in the recovery process.

Treatment for ED can include:

  • Therapy
  • Medication (such as Viagra)
  • Intracavernosal Injection
  • Intraurethral therapy
  • Testosterone Replacement Therapy
  • Vacuum constriction devices
  • Penile implants