Physiology of Pain.pdf

Physiology of Pain Dr Karishma Jeeboo  Registered Pharmacist for 20 years and have previous community pharmacy practice experience of over 16 years. Lecturer in Pharmacotherapeutics; Clinical And Community Pharmacy; and Clinical Supervisor. Director, School of Pharmacy, University of...

Physiology of Pain Dr Karishma Jeeboo  Registered Pharmacist for 20 years and have previous community pharmacy practice experience of over 16 years. Lecturer in Pharmacotherapeutics; Clinical And Community Pharmacy; and Clinical Supervisor. Director, School of Pharmacy, University of Guyana Chair, Pharmacy Council of Guyana Professional Assns. - CAP Education Chair and Secretary, Active member of the GPA. I love volunteerism and the Outdoors. I travel as far as I can to volunteer in Medical outreaches and missions.  Learning Outcomes Identification of the major physiological targets for drugs that are used for modulation and suppression of pain and pathological changes in body temperature. Identify the location of pain receptors on peripheral nerves. Identify methods of stimulation of pain receptors Outline the processes of nerve transmission of pain impulses from peripheral tissues to major areas of the brain Outline major neuronal processes in the brain that inhibit the transmission of pain impulses Outline the processes of body temperature regulation 05/09/2024 Dr Karishma Jeeboo 3  Introduction - Pain Most common symptom that causes people to seek healthcare Unpleasant, uncomfortable and usually means tissue damage If not managed properly – affects the patient’s QOL Individual assessment if important – each person perceives pain differently 05/09/2024 Dr Karishma Jeeboo 4  Types of Pain Two major types of pain: Nociceptive - involves the normal neural processing of pain that occurs when free nerve endings are activated by tissue damage or inflammation Neuropatic Involves the abnormal processing of stimuli from the peripheral or central nervous systems and is thought to serve no useful purpose. Damage to peripheral nerves or spinal cord 05/09/2024 Dr Karishma Jeeboo 5  Nociceptive Pain Nociception involves: Transduction Transmission Perception Modulation The complex mechanism of these 4 steps produces pain. Tissue damage that releases chemical mediators: Prostaglandins, bradykinins, serotonin, substance P and histamine 05/09/2024 Dr Karishma Jeeboo 6 Mechanism – Pain Process Chemical mediators activate nociceptors resulting in transduction (generation and transmission of action potential/ electrical stimulus). Transmission - action potential moves from the site of injury along afferent nerve fibers to nociceptors at the spinal cord. Release of substance P and other neurotransmitters carry the action potential across the cleft to the dorsal horn of the spinal cord. From where it ascends the spinothalamic tract to the thalamus and the midbrain. Finally, from the thalamus, fibres send the nociceptive message to the somatosensory cortex, parietal lobe, frontal lobe, and the limbic system, where the third nociceptive process -- perception -- occurs 05/09/2024 Dr Karishma Jeeboo 7  Perception Conscious experience of pain, involves both the sensory and affective components of pain. Modulation: final nociceptive process. Activation of the midbrain by activation of multiple types of neurons from this area that have a variety of neurotransmitters, including endorphins, enkephalins, serotonin (5-HT), and dynorphin, descend to lower areas in the central nervous system. Neurons stimulate the release of additional neurotransmitters, which ultimately trigger the release of endogenous opioids and inhibit transmission of the pain impulse at the dorsal horn 05/09/2024 Dr Karishma Jeeboo 8 05/09/2024 Dr Karishma Jeeboo 9 05/09/2024 Dr Karishma Jeeboo 10 05/09/2024 Dr Karishma Jeeboo 11 Fever  Rise in Temperature Part of the inflammatory process Deals with the body’s thermostat? As a result of the release of inflammatory mediators 05/09/2024 Dr Karishma Jeeboo 13  Temperature Control Chemical Mediators being released from injured cells, carried from the blood stream into your brain and raising the thermostatic set point to a higher level. What If you have your thermostat in your home raised from 70 to 80 to 85. That will cause the heater to turn on until it reaches that new higher set point. Leukocytic pyrogen and prostaglandins act on the hypothalamic neurons causing an increase in the thermostat set-point. 05/09/2024 Dr Karishma Jeeboo 14  15 05/09/2024 Dr Karishma Jeeboo  How do I get a Fever?? Interleukins and prostaglandins raise the set point. It’s generally believed that the greater the injury, the more of these chemicals are released and the greater the set point is raised. So let’s say your new set point is now 103°F and your actual body temp is 98.6°F - what happens? The Thermoregulatory Reflex Center COMPARES the two and thinks you are way colder than you should be! So what happens next? The control center is going to tell the body to warm your body up to 103°F! A fever! 05/09/2024 Dr Karishma Jeeboo 16  “Breaking” the Fever Healing tissue cells stop releasing chemicals -> set-point returns to normal -> activation of “cooling mechanisms” Let’s suppose there’s a viral infection, so it’s up to your immune system. There’s a wisdom to the body that allows us to survive these things. Either the virus kills you, and the story ends there, such as with the elderly with weak immune systems. Or, the cells start to heal and stop releasing the chemicals that cause fever (prostaglandins and interleukins), returning back to the normal set point. Still, now, your actual body temperature is at 103°F. Now what will happen? This will activate the homeostatic reflexes for cooling: You will feel very hot, the blood vessels in your skin will dilate (you’ll get red), and you’ll start to sweat. This is known as the “breaking” of the fever because the set point will return back to normal. 05/09/2024 Dr Karishma Jeeboo 17