Pathophysiology

· Pain Pathway o Because Pain is not a disease or disorder, but the outcome of contact with harmful or noxious stimuli, the pathophysiology is related to the Pain Pathway – the way in which pain is interpreted and counteracted by the brain. o Pain incorporates cognitive, behavioural and emotional responses from an individual, therefore knowing how pain manifests itself in a person is key to know how best to treat them. o Pain follows a simple pathway to the brain § Transduction, transmission, perception and modulation. · Transduction o a physiological process whereby a noxious mechanical, chemical, or thermal stimulus is converted/transduced via specialized receptors on primary afferent neurons into an electrical impulse or action potential.  <span style="line-height: normal; margin: 0cm 0cm 0pt 72pt; mso-add-space: auto; mso-list: l0 level2 lfo1; text-indent: -18pt;"><span style="font-family: 'courier new'; font-size: 12pt; mso-fareast-font-family: 'Courier New'; mso-fareast-language: EN-AU; msofareastfontfamily: 'courier new'; msofareastlanguage: en-au; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">This occurs at nociceptors, which are primary sensory neurons and are activated by intense stimuli <span style="line-height: normal; margin: 0cm 0cm 0pt 108pt; mso-add-space: auto; mso-list: l0 level3 lfo1; text-indent: -18pt;"><span style="font-family: wingdings; font-size: 12pt; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; mso-fareast-language: EN-AU; msobidifontfamily: wingdings; msofareastfontfamily: wingdings; msofareastlanguage: en-au; msolist: ignore;">§ <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Pressure, heat, mechanical insults (a surgical incision) or irritant chemicals <span style="line-height: normal; margin: 0cm 0cm 0pt 72pt; mso-add-space: auto; mso-list: l0 level2 lfo1; text-indent: -18pt;"><span style="font-family: 'courier new'; font-size: 12pt; mso-fareast-font-family: 'Courier New'; mso-fareast-language: EN-AU; msofareastfontfamily: 'courier new'; msofareastlanguage: en-au; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Strong physical stimuli (heat or pressure) and disease processes (inflammation) cause tissue damage and release a variety of chemicals. <span style="line-height: normal; margin: 0cm 0cm 0pt 108pt; mso-add-space: auto; mso-list: l0 level3 lfo1; text-indent: -18pt;"><span style="font-family: wingdings; font-size: 12pt; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; mso-fareast-language: EN-AU; msobidifontfamily: wingdings; msofareastfontfamily: wingdings; msofareastlanguage: en-au; msolist: ignore;">§ <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Some of these chemicals such as bradykinin, cholecystokinin and prostaglandins, activate or sensitize nearby nociceptors <span style="line-height: normal; margin: 0cm 0cm 0pt 72pt; mso-add-space: auto; mso-list: l0 level2 lfo1; text-indent: -18pt;"><span style="font-family: 'courier new'; font-size: 12pt; mso-fareast-font-family: 'Courier New'; mso-fareast-language: EN-AU; msofareastfontfamily: 'courier new'; msofareastlanguage: en-au; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Once released, these chemicals bind and activate specific receptors on the nerve endings increasing the excitability of the cell membrane leading to the generation of Action Potentials. <span style="font-family: symbol; font-size: 12pt; line-height: 115%; mso-bidi-font-family: Symbol; mso-fareast-font-family: Symbol; msobidifontfamily: symbol; msofareastfontfamily: symbol; msolist: ignore;">· <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Transmission <span style="line-height: normal; margin: 0cm 0cm 0pt 72pt; mso-add-space: auto; mso-list: l0 level2 lfo1; text-indent: -18pt;"><span style="font-family: 'courier new'; font-size: 12pt; mso-fareast-font-family: 'Courier New'; mso-fareast-language: EN-AU; msofareastfontfamily: 'courier new'; msofareastlanguage: en-au; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Once transduced and generated, action potentials (nerve impulses) are conducted to the central nervous system primarily via two types of primary afferent neurons <span style="margin: 0cm 0cm 0pt 144pt; mso-add-space: auto; mso-list: l0 level4 lfo1; text-indent: -18pt;"><span style="font-family: symbol; font-size: 12pt; line-height: 115%; mso-bidi-font-family: Symbol; mso-fareast-font-family: Symbol; msobidifontfamily: symbol; msofareastfontfamily: symbol; msolist: ignore;">· <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">A delta Fibres "Epricritic Pain" <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;"> <span style="margin: 0cm 0cm 0pt 180pt; mso-add-space: auto; mso-list: l0 level5 lfo1; text-indent: -18pt;"><span style="font-family: 'courier new'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Courier New'; msofareastfontfamily: 'courier new'; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Mechanical message <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;"> <span style="margin: 0cm 0cm 0pt 180pt; mso-add-space: auto; mso-list: l0 level5 lfo1; text-indent: -18pt;"><span style="font-family: 'courier new'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Courier New'; msofareastfontfamily: 'courier new'; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Sharp, Fast pain <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;"> <span style="margin: 0cm 0cm 10pt 180pt; mso-add-space: auto; mso-list: l0 level5 lfo1; text-indent: -18pt;"><span style="font-family: 'courier new'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Courier New'; msofareastfontfamily: 'courier new'; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Thin Myelinated fibres increase speed of processing <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;"> <span style="font-family: 'courier new'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Courier New'; msofareastfontfamily: 'courier new'; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">1st Order Sensory Neurons <span style="margin: 0cm 0cm 0pt 108pt; mso-add-space: auto; mso-list: l0 level3 lfo1; text-indent: -18pt;"><span style="font-family: wingdings; font-size: 12pt; line-height: 115%; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; msobidifontfamily: wingdings; msofareastfontfamily: wingdings; msolist: ignore;">§ <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Located in the dorsal root ganglia in the posterior of the spinal cord. <span style="font-family: 'courier new'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Courier New'; msofareastfontfamily: 'courier new'; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Nociceptive impulses travel along these peripheral nerve fibers (peripheral transmission) to the dorsal horn of the spinal cord where they synapse with the second order neurons(synaptic transmission). <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;"> <span style="font-family: 'courier new'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Courier New'; msofareastfontfamily: 'courier new'; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">2nd Order Sensory Neurons <span style="line-height: normal; margin: 0cm 0cm 0pt 108pt; mso-add-space: auto; mso-list: l0 level3 lfo1; text-indent: -18pt;"><span style="font-family: wingdings; font-size: 12pt; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; mso-fareast-language: EN-AU; msobidifontfamily: wingdings; msofareastfontfamily: wingdings; msofareastlanguage: en-au; msolist: ignore;">§ <span style="font-family: 'Times New Roman','serif'; font-size: 12pt;">Located in the dorsal grey column of the brainstem. <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">The impulse is further transmitted via neurons which cross the spinal cord and ascend to the thalamus and branches to the brainstem nuclei (central transmission). <span style="margin: 0cm 0cm 0pt 108pt; mso-add-space: auto; mso-list: l0 level3 lfo1; text-indent: -18pt;"><span style="font-family: wingdings; font-size: 12pt; line-height: 115%; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; msobidifontfamily: wingdings; msofareastfontfamily: wingdings; msolist: ignore;">§ <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Messages cross the cord and ascend to the thalamus via the Spinothalamic pathway, heading to th <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">e somatosensory cortex, the insula, frontal lobes and limbic system. <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;"> <span style="font-family: 'courier new'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Courier New'; msofareastfontfamily: 'courier new'; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Adelta and Cfibres slide <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;"> <span style="font-family: 'courier new'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Courier New'; msofareastfontfamily: 'courier new'; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Peripheral Transmission <span style="margin: 0cm 0cm 0pt 108pt; mso-add-space: auto; mso-list: l0 level3 lfo1; text-indent: -18pt;"><span style="font-family: wingdings; font-size: 12pt; line-height: 115%; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; msobidifontfamily: wingdings; msofareastfontfamily: wingdings; msolist: ignore;">§ <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Via the A-delta and C fibres along the Spinal Cord to the brain via the Spinothalamic Tract. <span style="font-family: 'courier new'; font-size: 12pt; line-height: 115%; mso-fareast-font-family: 'Courier New'; msofareastfontfamily: 'courier new'; msolist: ignore;">o <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Synaptic Transmission <span style="line-height: normal; margin: 0cm 0cm 0pt 108pt; mso-add-space: auto; mso-list: l0 level3 lfo1; text-indent: -18pt;"><span style="font-family: wingdings; font-size: 12pt; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; mso-fareast-language: EN-AU; msobidifontfamily: wingdings; msofareastfontfamily: wingdings; msofareastlanguage: en-au; msolist: ignore;">§ <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Action potential synapse at the dorsal horn of the spinal cord <span style="line-height: normal; margin: 0cm 0cm 0pt 108pt; mso-add-space: auto; mso-list: l0 level3 lfo1; text-indent: -18pt;"><span style="font-family: wingdings; font-size: 12pt; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; mso-fareast-language: EN-AU; msobidifontfamily: wingdings; msofareastfontfamily: wingdings; msofareastlanguage: en-au; msolist: ignore;">§ <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Neuroactive excitatory and inhibitory neurotransmitters are released from the Post synaptic nerve cell to the nociceptor terminal. <span style="line-height: normal; margin: 0cm 0cm 10pt 108pt; mso-add-space: auto; mso-list: l0 level3 lfo1; text-indent: -18pt;"><span style="font-family: wingdings; font-size: 12pt; mso-bidi-font-family: Wingdings; mso-fareast-font-family: Wingdings; mso-fareast-language: EN-AU; msobidifontfamily: wingdings; msofareastfontfamily: wingdings; msofareastlanguage: en-au; msolist: ignore;">§ <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">This leads to generation of action potentials across the synapses and central transmission of pain signals to higher centres.
 * __<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; line-height: 115%;">Pathophysiology __ **
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level4 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">C Fibres "Protopathic Pain"
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level5 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Mechanical and Thermal Stimuli
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level5 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Slow, dull, long lasting pain
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level5 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">unmyelinated fibres, slower response
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level1 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Perception
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level2 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">The process by which a noxious event is recognized as pain by a conscious person.
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level2 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Multiple areas of the brain are involved. There is no one location where perception occurs, although major defining components of pain are attributed to processes that take place in specific areas of the brain.
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level2 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">3rd Order Sensory Neurons
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level3 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">To the higher brain centres of Limbic system
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level3 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Frontal cortex, primary sensory cortex of the post central gyrus of parietal lobe
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level3 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">For example, the //sensory-discriminative// component is the result of activity in the somatosensory and the insular cortex, which allows the person to identify the type, intensity and bodily location of the noxious event.
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level3 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">The //affective-emotional// response to the noxious stimulus is mediated by the limbic system. Pain has an inseparable affective-emotional component that defines the response and associated behaviour resulting from the initiating noxious event or stimulus.
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level1 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Modulation
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level2 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"> ** The process of **// dampening or amplifying //** these pain-related neural signals. **<span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level2 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Descending input from the brainstem influences central nociceptive transmission in the spinal cord.
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level2 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Specific brainstem nuclei send projections to the dorsal horn of the spinal cord and when activated by ascending nociceptive impulses and other influences from the brain result in descending modulation.
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level2 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Though not completely understood, modulation results in descending inhibition of nociception through the release of neurotransmitters such as serotonin, norepinephrine and endogenous opioids.
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level2 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Gate Control Theory
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level3 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">Proposed by <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-ansi-language: EN-GB;">by Melzack and Wall in 1965 <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level3 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-ansi-language: EN-GB;">They believed there to be an ability for the body to reduce or increase the degree of perceived pain through modulation of incoming impulses at a gate located in the dorsal horn of the spinal cord. <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level3 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-ansi-language: EN-GB;">The integration of these inputs from sensory neurons, the spinal cord, and the brain, determined whether the gate will be opened or closed, either increasing or decreasing the intensity of the ascending pain signal. <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">
 * <span style="line-height: normal; margin: 0cm 0cm 10pt; mso-list: l0 level3 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto;"><span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-ansi-language: EN-GB;">There is a role for psychological variables in the perception of pain, including motivation to escape pain, and the role of thoughts, emotions, and stress reactions in increasing or decreasing painful sensations, this is evident in the gate control theory. <span style="font-family: 'Times New Roman','serif'; font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-AU;">