A common word which you ever heard in every moment of your life. Do you ever think about pain? What is pain? Why do we have pain? Why do we feel pain, is it good for our health or not? So come here and discuss pain. In today’s topic, we will discuss pain, the pathology of pain, the pathway of pain, How to stop the pain, etc.
What is Pain
Pain is an uncomfortable feeling in your body that warns you that something is wrong with your body. While this feeling is the body’s way of alerting your brain that there is any problem in your body, it can go on for weeks, months, or longer. Pain becomes a part of your existence. At that point, pain is not only a symptom but the disease itself. It can be steady, aching, throbbing, stabbing, pinching, or in many other ways.
Types of Pain:
7 Types of pain and a full list
Acute pain is a short-term pain that comes on suddenly and has a specific cause. Generally, it lasts for fewer than six months.
A common cause of acute pain includes
- Labor and childbirth
Pain that lasts for more than six months, even after the original injury is healed, is considered chronic pain.
A common example of chronic pain-
- . Headaches
- . Low back Pain
- . Arthritis Pain
- . Fibromyalgia Pain
- . Nerve damage Pain
It is the most common type of pain. It is caused by the stimulation of nociceptors, which are pain receptors for tissue injury.
It results from injuries or damage to internal organs. You can feel the pain in your trunk region which includes chest, abdomen, pelvis. It is often hard to pinpoint the exact location of visceral pain.
Common examples are-
- Irritable bowel syndrome
It results from stimulation of nociceptors in your tissues rather than your internal organs. This includes your skin, muscle, joints, connective tissues and bones. It is easier to pinpoint the location of somatic pain rather than visceral pain.
Common examples are-
- Bone fractures
- Strained muscles
- Connective tissue disease like osteoporosis
- Skin cuts, scrapes and burns
- Joint pain including arthritis pain
It results from damage to or dysfunction of the nervous system. Diabetes is the common cause of neuropathic pain.
Neuropathic pain is described as-
- Electric shocks
Pain that is perceived at the site different from its point of origin but innervated by the same spinal segment.
E.g. The pain associated with heart attack is commonly referred to the left arm, neck or chest.
How do we feel pain? When we touch anything our muscular control sends signals to the brain and our brain receives the signals and reads that signals and instructs to remove your hand from here or is there any pain which is a warning sign of any disease.
Nociceptors are the specialized sensory receptors with the ability to detect noxious stimuli and transform the stimuli into electrical signals that the central nervous system interprets. The free nerve endings of primary afferent A-delta and C fibres are responsible for nociception. Nociceptors respond to intense heat, cold, mechanical and chemical stimuli.
Primary Afferent Fibres
The A delta and c fibres that carry noxious sensory information, there are primary afferent fibres that carry non-noxious stimuli.
The axons of most second-order neurons cross the midline close to their level of origin to the contralateral side before they form the tract.
- They send their fibres to the thalamus, the reticular formation, the nucleus raphe magnus and the periaqueductal grey matter.
- This tract can be divided into medial and lateral tract
- Pseudounipolar cell (dorsal root ganglion) divides into central and peripheral branches.
- Impulses are transmitted by A-delta and C fibers
- These impulses are transmitted through the axons to the spinal cord.
- The cell body is located in the dorsal root ganglion.
- Axons of first-order neurons may synapse with interneurons, sympathetic neurons, and ventral neurons.
Secondary order Neurons Consists of
- Nociceptors specific primarily in LAMINAI
- Wide dynamic range neurons primarily in LAMINA 5
- Nociceptor-specific neurons serve only noxious stimuli but WDR neurons also receive nonnoxious afferent input from A beta, A-delta, and C fibers.
- Cell body in the spinal cord or medulla oblongata.
Laminal 2 also called the SUBSTANSIA GELATINOSA, contains many interneurons. It is believed to be a major site of action for opioids.
Lamina 5 contains WDR neurons, responds to both noxious and nonnoxious sensory input, and receives both visceral and somatic pain afferents. Thus responsible for referred pain.
Located in the thalamus and send fibres to somatosensory areas 3 1 2 in the postcentral gyrus of the parietal cortex.
Perception and discrete localization of pain takes place in these cortical areas.
Modulation of Pain
“Ronald Melzack and Petrick Wall” proposed the pain gate control theory.
It suggests that the signals encounter ‘nerve gates’ at the level of the spinal cord.They need to get cleared through these gates to reach the brain. They are-
- The intensity of the pain signals
- The intensity of the other sensory signals (touch, temperature and pressure), if generated at the site of injury.
- The message from the brain itself (to send the brain signals or not).
The gate = spinal cord interneurons that release opioids.
The synaptic junctions between the peripheral nociceptors fibre and the dorsal horn cells in the spinal cord are the sites of considerable plasticity.
A “Gate” can stop pain signals arriving at the spinal cord from being passed on to the brain.
- The intensity of the pain signals
- The intensity of the other sensory signals (touch, temperature and pressure), if generated at the site of injury
- The message from the brain itself (to send the brain signals or not)
Supraspinal structures send fibres down the spinal cord to inhibit pain in the dorsal horn.
Important sites of origin for these pathways include the periaqueductal grey matter, reticular formation and nucleus raphe magnus.
Stimulation of periaqueductal grey area in the midbrain produces widespread analgesia in humans. Axons from these tracts act presynaptically on primary afferent neurons and postsynaptically on second order neurons
Pain modulation via Analgesic Pathway
These pathways mediate their antinociceptive action via adrenergic, serotonergic, and opiate receptor mechanism.
The role of monoamines in pain inhibition explains the analgesic action of antidepressants that block reuptake of catecholamines and serotonins.