The Phases, Treatment, and Types of Nociceptive Pain

Nociceptive pain is a type of pain caused by an injury, physical pressure, or inflammation of some part of the body. There are two types of nociceptive pain: Somatic, which originates in your arms, legs, face, muscles, tendons, and superficial areas of your body, and visceral, which originates from your internal organs (for example, a stomachache or pain from a kidney stone).

Unlike neuropathic pain, which is caused by nerve hypersensitivity or dysfunction (for example, diabetic neuropathy or phantom limb pain), nociceptive pain involves the activation of pain receptors by a stimulus that normally causes pain (think, bumping your arm on a table, breaking a bone, or feeling pain from an inflamed appendix).

What Are Nociceptors?

Both somatic pain and visceral pain are detected by nociceptors, which are sensory nerves that detect acute pain due to tissue injury, as well as chronic pain due to swelling or inflammation. These sensory nerves are located throughout the body in the skin, bones, joints, muscles, and tendons, as well as in the internal organs, such as the stomach, bladder, uterus, and colon.

Nociceptors respond to painful stimuli by tiny specialized nerve endings that are activated by temperature, pressure, and stretching in and around their surrounding tissues.

Types

Though somatic and visceral pain is detected by the same types of nerves, and the triggers for both types of pain are sometimes similar, they do not usually feel the same. 

Somatic Pain

Somatic pain, felt like a sharp pain, dull ache, or throbbing sensation, is detected by the nerves located in the skin, subcutaneous tissues, muscles, and joints. It can be triggered by an acute injury or by a chronic process.

The pain felt from a cut, bruise, or arthritis are examples of somatic pain.

Visceral Pain

Visceral pain is detected by nociceptors in the body's internal organs. You might feel visceral pain if you have a stomach infection, constipation, or something more serious such as internal bleeding or cancer. 

Unlike somatic pain, you might not feel visceral pain exactly at the area that is injured or inflamed. In other words, visceral pain can be felt further away from its actual origin; this is called referred pain.

Another difference between somatic and visceral pain is that visceral pain may be associated with other symptoms like nausea, vomiting, or jitteriness, which less commonly occurs with somatic pain.

Phases

When nociceptors detect physical damage to your body, they create electrical signals. The signals travel to your spinal cord, which then sends the message up to the brain. 

This process occurs rapidly, involves four key steps, and is the same for both somatic and visceral nociceptive pain:

1. Transduction: Tissue injury (bumping your arm on a table) triggers the release of chemicals (for example, substance P or prostaglandins) within the body, which then excites the nociceptive nerve fibers.
2. Transmission: During this phase, the "pain message" moves from your skin, bones, joints, or internal organs toward your spine and then up to the brain. It first reaches the brainstem, then moves up to the thalamus, and finally to the cerebral cortex, where your brain has a "map" that registers the exact location of your pain.  
3. Perception: In this phase, you become aware or conscious of the pain, which is the perception of pain.
4. Modulation: This final phase is when your brain interacts with your nerves to modulate or alter the pain experience (for example, to adjust the intensity and duration). Modulation involves the release of chemicals, such as endorphins and serotonin, that reduce the transmission of pain signals.

The concepts of pain threshold (when a sensation becomes "painful") and pain tolerance (the amount of pain a person endures) also fit into this stage. A person's pain threshold and tolerance are based on a number of factors, both learned and inherited.

Chronic Nociceptive Pain

Most of the time, nociceptors stop firing once the injury or illness has resolved, which may require treatment, healing time, or both, depending on the underlying cause. You have probably noticed this when you have recovered from a cut, a broken bone, or an infection.

Sometimes, however, the body can release substances that make nociceptors more sensitive even after an injury has healed, causing them to continue to fire. For example, when a painful condition is prolonged, the repetitive stimulation can sensitize the neurons for the long-term, resulting in excessive reactivity to pain.

This can lead to chronic pain issues such as headaches, arthritis, fibromyalgia, and pelvic pain.

Treatment

Treatment of nociceptive pain depends on the specific injury, and whether the pain is acute or chronic. For example, an acute injury like a hard bump on a table may simply require ice or a one-time dose of nonsteroidal anti-inflammatory (NSAID) like ibuprofen. On the other hand, chronic pain, like from fibromyalgia, may require a daily medication to thwart pain signaling.

More specifically, when it comes to medications, most target one of the four pain phases. For instance, NSAIDs target the first phase (transduction) by reducing prostaglandins, thus decreasing the activation of nociceptors. Likewise, an epidural spinal injection for a bulging or herniated disc also targets phase one.

On the other hand, opioids and antidepressants target phase four (modulation), so they work by inhibiting the pain signals that are sent along the nerve pathway.

Of course, besides medications, there are a plethora of other therapies used to treat nociceptive pain, with some examples including:

• Physical therapy
• Alternative treatments like biofeedback or acupuncture
• Hot and cold therapy
• Surgery (for example, for pain from a visceral problem, like appendicitis)

A Word From Verywell

While nociceptive pain may be distressing, the good news is that it's generally responsive to pain medications like NSAIDs or opioids. These can usually control the pain until the body heals itself (think a broken bone in a cast or a paper cut) or the underlying problem is resolved (think passing a kidney stone or a surgeon removing an inflamed appendix).