PSY 325 1st EditionExam # 2 Study Guide Lectures: 8-13 (excluding 12) Lecture 8 Chronic Pain: Understanding and Managing PainWhat is Pain? Pain begins with sense receptors on or near the surface of the body. These receptors change physical energy like light, sound, heat and pressure into neural impulses. Most of the pain we experience originates as stimulation to the skin and muscles. Neural impulses that start in the skin and muscle are part of the peripheral nervous system (PNS). All neurons outside the brain and spinal cord (the CNS) are part of the PNS. Tracing the path of neural impulses from the receptors to the brain is a way to comprehend the physiology of pain.Pain can be defined as “an unpleasant sensory and emotional experience associated with actualor potential tissue damage, or described in terms of such damage.”Pain is remarkably difficult for people to define; it is an unpleasant sensory and emotional experience. We are starting to see pain as having an emotional component as well.Pain is not simply the result of tissue damage. The experience is situational, objective, and cultural. A lot of different things about us can affect our personal experience.Purpose of pain—those who cannot feel pain have a rare genetic disorder called congenital insensitivity to pain. Many people with this disorder die at a pretty young age due to health problems that could have been treated if they were able to heed the warning signs that pain provides. Pain is necessary for survival however because it is the body’s way of calling attention to injury. Understand the general physiology of pain- Somatosensory system—conveys sensory information from the body to the brain. It consists of several senses, including touch, light and deep pressure, cold, warmth, tickling, movement, and body positiono Afferent neurons—are one of three types (afferent, efferent, and interneurons). Afferent( sensory) relay information from the sense organs toward the brain. Efferent (motor) neurons result in the movement of muscles or the stimulation of organs or glands. Interneurons connect sensory to motor neurons. Sensoryneurons called primary afferents with specialized receptors that convert physical energy into neural impulses which travel to the spinal cord and then to the brain, where that information is processes and interpreted. Nociception refers to the process of perceiving pain. The skin is the largest of the nociceptors. Some neurons are covered with myelin. A-fibers with this fatty insulation on them travel neural impulses faster than unmyelinated C fibers do. There are two important types of A fibers: A-beta fibers and the smaller A-delta fibers. C fibers require more stimulation to fire but are more common than A-fibers. A-delta fibers produce “fast” pain that is sharp or pricking. C-fibers often result in a slower developing sensation of burning or dull aching.- Spinal cord—an avenue for sensory information traveling toward the brain and motor information coming from it. The spinal cord also produces the spinal reflexes. The afferent fibers group together after leaving the skin and this grouping forms a nerve.o Neuron fibers extend into the dorsal horns of the spinal cord. Dorsal horns have several layers of laminae. - Brain (somatosensory cortex in particular)—o Includes a map of the skin, with more of the cortex devoted to areas of the body richer in skin receptorso The thalamus receives information from afferent (sensory) neurons in the spinal cord. After making connections in the thalamus, the information travels to other parts of the brain including the somatosensory cortex- located in the cerebral cortex. o Referred pain—when pain is experienced in a part of the body other than the site where the pain stimulus originates. - Neurotransmitters—chemicals that are synthesized and stored in neurons. Researchers have shown that the neurochemistry of the brain plays a role in the perception of pain. Receptors in the brain are sensitive to opiate drugs; that is some neurons have receptor sites that opiate drugs are capable of occupying and activating. This explains how opiates reduce pain by fitting into brain receptors, modulating neuron activity and alter pain perceptiono These neurochemicals seem to be one of the brain’s mechanisms for modulating pain. Stress, suggestion and electrical stimulation The modulation of painThe Periaqueductal gray is involved in modulating pain. Neurons in this area run down into the reticular formation and the medulla (lower part of the brain that is involved in pain perception). Types (or stages) of pain—1. Acute pain—pain from cuts, burns, childbirth, surgery, dental work, and other injuries. Its duration is normally brief. It is adaptive and signals the person to avoid further injury.2. Prechronic pain—the most crucial stage of pain which comes between the acute and the chronic stages. The person, at this stage, either overcomes the pain at this time or develops the feelings of fear and helplessness that can lead to chronic pain3. Chronic pain—endures over months or even years. It may be due to a condition such as rheumatoid arthritis or it may be the result of an injury that persists beyond the time of healing. It is NOT adaptive, rather it can be debilitating and demoralizing and lead to feelings of helplessness and hopelessness. Chronic pain does not ever have a biological benefit.Another type of pain is chronic recurrent pain—pain marked by alternating episodes of intense pain and no pain (headache pain is an example).Factors influencing pain:C.A. Strong and others conceptualized pain to include two factors: the sensation and theperson’s reaction to that sensation. This view put organic causes and psychological factors at the same level of importance. New definition of pain and an altered view of the experience came along.Theories of Pain– Specificity theory:o Hypothesizes that specific pain fibers and pain pathways exist, making the experience of pain virtually equal to the amount of tissue damage or injury. Descartes proposed that the body works mechanically. His view said that the mind works by a different set of principles and body and mind interact in a limited way. Researchers tried to find out which type of receptor conveyed what type of sensory information. The attempt failed. Some parts of the bodycontain only one type of receptor yet those areas feel a full range of sensations. - Gate-control theoryo