UNIT VII: PAIN

Objectives: By the end of this lecture the students will be able to : Review the concept of somatosensory pathway. Describe the function of Nociceptors in response to pain information. Describe the function of endogenous analgesic mechanism as they relate to transmission of pain information. Describe the proposed mechanism of pain relief associated with the use of heat, cold & TENS i.e. Transcutaneous electrical nerve stimulation

Somatosensory Pathway Sensory pathways consist of the chain of neurons, from receptor organ to cerebral cortex, that are responsible for the perception of sensations.

Nociceptor A nociceptor is a sensory neuron that responds to potentially damaging stimuli by sending signals to the spinal cord and brain. This process called nociception, usually causes the perception of pain. It is the afferent activity.

Pain An unpleasant sensation associated with actual or potential tissue damage. Pain is an unpleasant or emotional experience Pain is an unpleasant or emotional experience originating in real or potential damaged tissue originating in real or potential damaged tissue Unpleasant sensations (Sensory and emotional) associated with either potential or actual tissue damage.

Pain Stimuli Phospholipids are converted to Arachidonic Acid by phosholipase AA is converted to Prostaglandins by cycloxygenase-II

Acute pain Acute pain is a protective mechanism that alerts the individual to a condition or experience that is immediately harmful to the body. Sudden onset, short duration, severe It lasts less than 6 months It often results from injury, surgery It is presenting symptoms of some infections i.e. pharyngitis, appendicitis, otitis media etc.

Chronic Pain Continuous, long term processContinuous, long term process Lasts more than 6 months.Lasts more than 6 months. Examples: Back pain, cancer pain, arthritisExamples: Back pain, cancer pain, arthritis

Conti Cutaneous pain It is superficial coming from the skin or close to the surface of the body.It is superficial coming from the skin or close to the surface of the body. It is sharp painIt is sharp pain Deep somatic pain Deep somatic pain originates from deep structuresDeep somatic pain originates from deep structures i.e. muscles, joints, blood vessels etc.i.e. muscles, joints, blood vessels etc.

Conti Visceral pain Visceral pain refers to pain in internal organs, the abdomen, or chest.Visceral pain refers to pain in internal organs, the abdomen, or chest. i.e. renal pain, peptic ulcer pain, pain in cholecystitis etci.e. renal pain, peptic ulcer pain, pain in cholecystitis etc Referred pain Referred pain is pain that is present in an area distant from its point of origin. The area of referred pain is supplied by the nerves from the same spinal segment as the actual site of pain. i.e. MI pain etc. Referred pain is pain that is present in an area distant from its point of origin. The area of referred pain is supplied by the nerves from the same spinal segment as the actual site of pain. i.e. MI pain etc.

Naturopathic Pain It is caused due to peripheral nerves damage.i.e. Trigeminal neuralgia. Neuralgia It is characterized by severe, brief, often repetitive attacks of throbbing pain.

Endogenous Analgesia System Endogenous capability of the brain itself to suppress the input of pain signals to the nervous system by activating a pain control system, called an analgesia system.

Endorphin and enkephalin Endorphin and enkephalin are the body's natural painkillers. When a person is injured, pain impulses travel up the spinal cord to the brain. The brain then releases endorphins and enkephalins. Enkephalins block pain signals in the spinal cord. Endorphins are thought to block pain principally at the brain stem.

TENS is the method of applying minute amounts of electrical stimulation to a large diameter nerve fibers via electrodes placed on the skin. TENS (Transcutaneous electrical Nerve stimulation)

Cont… Presynaptic inhibition in the dorsal horn of the spinal cord Endogenous pain control (via endorphins, enkephalins) Direct inhibition of an abnormally excited nerve Restoration of afferent input

Cold therapy Cold slows down blood flow to an injury, thereby reducing pain and swelling. Cold therapy slows circulation, reducing inflammation, muscle spasm, and pain. It should be used if the area is swollen or bruised.

Heat therapy Heat opens up blood vessels, which increases blood flow and supplies oxygen and nutrients to reduce pain. The warmth also decreases muscle spasms and can increase range of motion.

References Porth, MC. (6th ED). Pathophysiology. (2002). Philadelphia. USA. Lippincott Willams& Willkins, A Wolters Kluwer Company McPhee, J. S., & Papadakis, A. M. (2011). Current Medical Diagnosis and Treatment. (50 th ED). Chicago. USA: Mc Graw Hill