What is Pain?

Pain can be defined in many ways. It is usually described as a distressing sensation in a particular part of the body or, an unpleasant or hurtful sensation resulting from the stimulation of nerve endings. However, pain can also be explained as a mental or emotional suffering or torment.

Why is there Pain?

Pain is said to be a part of the body's defence system, triggering a reflex reaction to retract from a painful stimulus. It helps adjust behaviour to increase avoidance of that particular harmful situation in the future.

What causes Pain?

Various daily activities and actions may cause pain and aches. For example, a pinch from someone or engaging in strenuous exercises that can lead to muscle aches. Occasionally, pain also occurs through serious injuries and illnesses such as road accidents and sore throats.

Cytokines, a type of protein found in the nervous system, also part of the body's immune system and the body's shield for fighting off disease can also trigger pain. It promotes inflammation even in the absence of injury or damage. Certain types of cytokines have been linked to nervous system injury. After trauma, cytokine levels rise in the brain, spinal cord and at the site in the peripheral nervous system where the injury occurred. Below is a picture of cytokines.

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How Pain occurs?

Pain is a complicated process that involves an intricate interaction between a number of important chemicals found naturally in the brain and spinal cord. In general, these chemicals called neurotransmitters transmit nerve impulses from one cell to another.
Receptors on the skin activate a series of events upon receiving a stimulus. It begins with an electrical impulse that travels from the skin to the spinal cord where the stimulus is carried by nerve fibres. The picture below shows the pain receptors found in the skin.

The body's chemicals act in the transmission of pain messages by stimulating neurotransmitter receptors found on the surface of cells. Each receptor has a corresponding neurotransmitter.
Receptors function much like gates that enable pain messages to pass through and on to the neighbouring cells.
The spinal cord acts as a relay centre where pain signals can be blocked, enhanced, or otherwise modified before it is relayed to the brain. One area of the spinal cord in particular, called the dorsal horn is important in the reception of pain signals.
The most common destination in the brain for pain signals is the thalamus and then the cortex, the headquarters for complex thoughts. This is where the signals are interpreted as pain.

There are many different neurotransmitters in the human body acting in various combinations to produce painful sensations in the body. Some chemicals govern mild pain sensations while others control intense or severe pain.
A type of receptor that responds to painful stimuli is called nociceptors. Nociceptors are thin nerve fibres in the skin, muscle, and other body tissues, that when stimulated, carry pain signals to the spinal cord and brain. Normally, nociceptors only respond to strong stimuli such as a pinch. However, when tissues become injured or inflamed, chemicals are released making nociceptors much more sensitive causing them to transmit pain signals in response to even gentle stimuli such as breeze or a caress. This condition is called allodynia; a state in which pain is produced by harmless stimuli.


Pain is sometimes felt not only at the site of stimulation but in other parts of the body supplied by nerves in the same sensory path for example, the pain of angina pectoris or coronary thrombosis may extend to the left arm. This phenomenon is known as referred pain.

This is a simple video showing how pain occurs.

How can Pain be reduced?

The brain is able to send signals that release painkillers found in the spinal cord. These painkillers include serotonin, norepinephrine and opioid-like chemicals.

Pain may be modified by sedatives and Nonsteroidal Antiinflammatory Drugs (NSAIDs) or, if unusually severe, by opioid narcotics. In this case, the important receptors in pain transmission are opiate-like receptors. Morphine and other opioid drugs work by locking on to these opioid receptors, switching on pain-inhibiting pathways or circuits, and thereby blocking pain.

Recently, patient-controlled analgesic techniques have been introduced; in which patients have the option of injecting small quantities of narcotic type analgesics to control their own pain.

Another way to control pain is by inhibiting hormones called prostaglandins. Prostaglandins stimulate nerves at the site of injury and cause inflammation and fever. Certain drugs, including Nonsteroidal Antiinflammatory Drugs (NSAIDs), act against such hormones by blocking the enzyme that is required for their synthesis.

Acupuncture, meditation, massages and other medications such as ointments and balms can help to reduce pain too.

Topical Capsaicin, a type of chilli pepper extract is believed to reduce pain of certain illnesses. However, it does promote some side effects.

Some people also believe that pain can be controlled by the mind.