How We Feel Pain
Pain is a complex physiological process. A pain message is transmitted to the brain by specialized nerve cells known as nociceptors, or pain receptors . When pain receptors are stimulated by temperature, pressure or chemicals, they release neurotransmitters within the cells. Neurotransmitters are chemical messengers in the nervous system that facilitate communication between nerve cells.
As seen in the diagram, these messengers transmit a pain signal from the pain receptor to the spinal cord, and then to the thalamus, a region of the brain. The thalamus then transmits the pain signal to other areas of the brain to be processed.
Once the brain has received and interpreted the pain message, it coordinates an appropriate response. The brain can send a signal back to the spinal cord and nerves to increase or decrease the severity of pain. For example, the brain can signal the release of natural painkillers known as endorphins. Alternately, the brain can direct the release of neurotransmitters that enhance pain or hormones that stimulate the immune system to respond to an injury. Recent research has shown that people possess differing amounts of these neurotransmitters, possibly explaining why some people experience pain more intensely than others. Furthermore, recent studies have found that genetic makeup can influence an individuals sensitivity to pain.
Types of Pain
Optogenetic Stimulation Of Specific Nociceptor Populations In Mice
In contrast to the approach taken by Zlyka et al. in which channelrhodopsin was inserted into the locus of a low abundance marker of a subset of nociceptors, the Nav1.8-Cre approach may be more useful for behavioral studies, and investigations of spinal and supraspinal activation, given that a greater number of nociceptors will be activated in this way.
The Impact Of Anxiety And Depression On The Brain
No one wants to be in pain. The unpleasant feelings of pain cause depression and anxiety in many people. This, too, becomes a vicious cycle. Our mood impacts our nociception and influences whether or not the brain decides that the pain response is necessary. This feeling of pain can make us feel anxious, triggering the fight-or-flight response. The fight-or-flight response stiffens our muscles, negatively impacts our sleep, and prevents the body from properly regulating itself. All of these additional factors may lead to more pain.
So how do we break this cycle? Many recommend cognitive behavioral therapy . CBT operates on the principle that our thoughts and feelings make us who we are. Our thoughts influence how we see the world, make judgments about ourselves, and experience pain. By addressing memories of pain or our expectations of pain through CBT, we may find that our pain is reduced and we can live life with less anxiety.
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Transcutaneous Electrical Nerve Stimulation
Pain perception is transferred to the brain through the dorsal horn of the medulla spinalis. Pain sensation is mainly mediated by small nerve fibers , whereas touch and pressure sensations are transferred by large nerve fibers . Some conditions may affect this transmission according to the gate-control theory, described by Melzack and Wall in the mid-1960s . Transmission cells and inhibitory interneurons control this transmission traffic together. Increased stimulation of the large fibers compared to small fibers causes inhibitory neuron stimulation, resulting in less sensation of pain.
Fig. 3. Transcutaneous electrical nerve stimulation according to INFLATE . Electrode attachment sites are shown on the abdominal wall and posterior surface . The TENS device with electrode connections . T1112 shows the thoracal 1112 dermatome lines both on anterior and posterior surfaces. Symp, symphysis pubis.
William Renthal, in, 2020
Optopharmacology And Novel Optoreceptors In Pain Research
Another approach has been the recent development of a photoactive MOR, the main receptor mediating the analgesic actions of morphine . This study designed a recombinant receptor, containing the optically active component of the rhodopsin molecule and the parts of the mu opioid receptor responsible for MOR receptor protein and G protein signaling. In a HEK cell system, this receptor is activated by light and has the ability to activate endogenous MOR receptor intracellular signaling pathways. Further development would be required, but expression of this mutant MOR receptor could be a useful way to overcome the side effects of MOR mediated analgesia, including analgesic tolerance, which is associated with alterations in MOR signal transduction pathways. Future work will determine if selective activation of the MOR in the periphery by light application prevents the CNS problems in patients requiring long term morphine treatment.
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The Role Of Nerves In Identifying Pain Sensations
Lets say you step on a rock. How does a sensory nerve in the peripheral nervous system know this is any different than something like a soft toy? Different sensory nerve fibers respond to different things and produce different chemical responses which determine how sensations are interpreted. Some nerves send signals associated with light touch, while others respond to deep pressure.
Special pain receptors called nociceptors activate whenever there has been an injury, or even a potential injury, such as breaking the skin or causing a large indentation. Even if the rock does not break your skin, the tissues in your foot become compressed enough to cause the nociceptors to fire off a response. Now, an impulse is heading through the nerve into the spinal cord, and eventually all the way to your brain. This happens within fractions of a second.
Brain Areas In The Neuromatrix And The Changes Due To Chronic Pain
Studies using functional MRI have identified six common regions activated in acute pain. These regions include the primary somatosensory cortex , secondary somatosensory cortex , anterior cingulated cortex, insular cortex, prefrontal cortex and the thalamus. It is these regions that make up the pain neuromatrix which Melzack has identified. More information on the Neuromatrix Theory of Pain and the Mature Organism Model can be found on the Multidimensional Nature of Pain page and on Louis Gifford’s website here.
The secondary somatosensory cortex is associated with the discrimination of pain intensity. There has been shown to be a co-activation between the primary somatosensory cortex and the secondary somatosensory cortex. In patients with chronic pain, there is a bilateral activation pattern, as compared to a contralateral activation pattern as seen in acute pain. This indicates that there is less of a representation of the initial pain and again may contribute to the widespread, vague pain described by chronic pain patients.
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What Role Does The Spinal Cord Play In Response To Pain
The complexity of the spinal cord, with all its bundles of nerves transmitting all sorts of signals back and forth from the brain at will. Calling it the Indy 5000 for motor and sensory impulses would fit well. Look at your spinal cord like the office manager, not only does it send and receive messages it also makes basic decisions, known as reflexes.
At the same time directing impulses to the brain and back down the spinal cord to the injured area is the information hub. The information hub is an area of your spinal cord known as the dorsal horn. So, when you stepped on that truck, the first impulse was to quickly lift your foot, right? Thats because your dorsal horn had already sent the message. So again, your spinal cord is like an office manager, but your brain is the CEO running the show.
DRG neurons arise from the spinal nerves of the dorsal root, which carries sensory messages from several receptors, inclusive of the response from the nervous system towards pain and temperature. Ask your specialist at Southeast Pain & Spine Care if Dorsal root ganglion stimulation could be an option for your chronic pain.
Effects Of Chronic Pain On Cognition And Working Memory
Working memory refers to the short term, information retention system which is essential to the skill of maintaining and manipulating behaviourally relevant information. Effective working memory function is necessary for guiding behaviour, making decisions and reasoning and planning. Chronic pain patients often display cognitive or working memory deficits and are often impaired in the performance of cognitively demanding tasks.
There have been a number of studies which have tried to understand how an increased attention to pain can then lead to decreased working memory. Walteros et al compared fifteen patients with fibromyalgia and fifteen healthy patients and looked at how they performed the Iowa Gambling Task and a conditional associative learning task. The results showed that fibromyalgia patients had a poorer performance than healthy controls in both tasks. The patients with fibromyalgia displayed more errors in the learning task and more disadvantageous decisions in the gambling task.
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What The Nervous System Is And Does
There are two main parts that make up the nervous system the brain and spinal cord which in combination forms the central nervous system including your motor and sensory nerves, which makes up the peripheral nervous system.
You see, the brain and spinal cord receive signals from your nerves while sending out large patterns of signals to the muscles controlling your arms, legs, and spinal movements. The spinal cord consistently receives updates to your sensors that detect your muscle flexibility, endurance and strength.
So in a nutshell, sensory nerves send impulse updates to your brain through your spinal cord. The brain then sends updates to the motor nerves, which is the reason why we perform actions.
How The Nervous System Detects And Interprets Pain
How your nervous system detects and interprets pain is nothing short of miraculous. Think about it. How does your brain know the difference from feather touch to a pinch, or what about the fact that your brain knows when youre in pain?
So, does that mean that if the pain signal doesnt make it to your brain that you wont feel any pain? And how does your body know when to produce pain in a specific part of your body? Does your brain send signals to tell your body whether pain will be acute or become chronic? So many questions, and too many complex answers that the layperson cant comprehend, so what do you do?
We can help you to understand the basics of how your nervous system detects and interprets your pain in a way that you can understand. With a focus on interventional pain procedures, supporting medications and advanced therapies to help you control and relieve your pain.
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Nociception And Pain: Lessons From Optogenetics
- Fishberg Department of Neuroscience, Department of Pharmacology and Systems Therapeutics and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
The process of pain perception begins in the periphery by activation of nociceptors. From here nociceptive signals are conveyed via the dorsal horn of the spinal cord to multiple brain regions, where pain is perceived. Despite great progress in pain research in recent years, many questions remain regarding nociceptive circuitry and behavior, in both acute nociception and chronic pain states. Techniques that allow for selective activation of neuronal subpopulations in vivo can provide a better understanding of these complex pathways. Here we review the studies to date that have employed novel optogenetic tools to improve our understanding of the pain pathway at the peripheral, spinal and supraspinal levels.
Experiencing Pain Involves Multiple Brain Pathways And Can Be Self
Posted January 13, 2015
A study from the University of Colorado at Boulder released on Jan. 12, 2015, reports that the ability to use your thoughts to modulate perceptions of pain utilizes a completely separate brain pathway than the pathway used to send the physical pain signal to your brain. This discovery is a breakthrough.
As an ultra-endurance athlete, I have regularly used a technique called cognitive self-regulation to manage my perceptions of pain. Can you think of times in your life when changing your explanatory style and mindset has helped minimize your perceptions of pain?
This new study helps explain how cognitively controlling different pain pathways allowed me to compete in races like the Badwater Ultramarathon, which is a 135-mile run through Death Valley in July win the Triple Ironman, which is a 7.2-mile swim, 336-mile bike and 78.6-mile run done nonstop and break a Guinness World Record by running 153.76 miles on a treadmill in 24 hours.
Ultimately, the ultra-endurance athlete who can subject him or herself to the most intense levels of physical suffering and continue moving forward the fastest wins the race.
Christopher Bergland crossing the finish line of a Triple Ironman after 38 hours nonstop.
The January 2015 CU-Boulder study, Distinct Brain Systems Mediate the Effects of Nociceptive Input and Self-Regulation on Pain, was published in the journal PLOS Biology.
What cognitive methods work best for minimizing perceptions of pain?
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What Is The Role Of The Nerves In Relation To Identify Pain Sensations
Some nerves send signals related to light touch, while others react to intense pressure. For instance, if you accidentally step on a toy truck left lying around, how is your sensory nerve in the peripheral nervous system able to decipher the difference in pain sensations? Well, thats because different sensory nerve fibers produce different chemical responses that are able to interpret the different sensations as well as reacting to it.
Whenever an injury happens, special pain receptors called nociceptors are activated. Remember the toy truck from earlier? Well, lets say that when you stepped on that truck luck was on your side, and you didnt break any skin. Your nociceptors will still shoot off a response from your nerve, through the spinal cord, en route to your brain due to the compression of the tissues in your foot from stepping on the toy truck.
What Part Of The Brain Registers Pain
The brain stem, thalamus and cerebral cortex are the three structures of the brain that receive and process sensations of pain, according to BrainFacts.org. Different parts of the cerebral cortex are involved with painful sensations originating from specific parts of the body. Pain processing occurs in the sensory cortex.
Other regions of the brain are also associated with the perception of pain, according to Macalester College. Pain signals reach the brain through two different pathways, known as the fast pathway and the slow pathway. The fast pathway connects to the thalamus through A-delta fibers, which are neural pathways that transmit sensory information regarding pain and temperature to the brain. After pain signals reach the thalamus, they are then transferred to the sensory and motor sections of the cortex for further processing.
The slow pathway, as the name suggests, transmits pain signals less quickly than the fast pathway. The slow pathway begins with C-fibers detecting a painful stimulus through chemical, pressure or temperature changes. The C-fibers transmit sensory information to the dorsal horn of the spinal cord, activating the central nervous system. The sensory information travels through the central nervous system to various areas of the brain, including the prefrontal cortex, the amygdala and the hypothalamus. The slow pathway is associated with the emotional reaction that occurs in response to painful stimuli, states Macalester College.
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Summary And Clinical Applicability
Research into placebo responses has shed light on several brain neural network modulating pain perception. Pain relief through distraction suggests that pain experience can be modified, and highlights the influence cognitive processes have on pain perception. The concept of pain as an actively constructed experience that is determined by expectations has implications for chronic pain prevention and treatment, so that patients with chronic pain might be good candidates for placebo intervention.
Brain Responses To Verbal And Pain Thermal Stimuli Over The Entire Experiment
Brain activity related to experimenters comments, thermal noxious stimuli, and fluctuation of pain intensity perception were examined for the whole fMRI experiment across all the conditions, and thresholded at p< 0.01 corrected . Verbal stimuli were associated with brain activity in the auditory network. Thermal noxious stimuli activated cortical areas commonly related to nociceptive stimuli while conscious pain intensity ratings were mainly associated with brain activity changes in the anterior mid-cingulate , anterior insula and dorsolateral prefrontal cortex . More details are reported in Fig. . For the full list of activated brain regions see Supplementary Table .
Most of the changes in FC concerned the comparisons between Empathetic minus Neutral conditions: In the Empathetic condition time-series correlations increased between right pI and bilateral vmPFC areas, between both anterior insular cortices, between right anterior insula and right vmPFC > 2.90, p< 0.007). The FC between left vmPFC and right PCC/Prec =3.27, p=0.003 Fig. ).
FC increased significantly in empathetic conditions between left anterior insula and right vmPFC and decreased between right PCC/Prec and left vmPFC =3.51, p< 0.001) as compared to the Unempathetic conditions.
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The Role Of The Spinal Cord In Pain Response
Your spinal cord is a complex array of bundles of nerves, transmitting all kinds of signals to and from the brain at any given time. It is a lot like a freeway for sensory and motor impulses. But your spinal cord does more than act as a message center: it can make some basic decisions on its own. These decisions are called reflexes.
An area of the spinal cord called the dorsal horn acts as an information hub, simultaneously directing impulses to the brain and back down the spinal cord to the area of injury. The brain does not have to tell your foot to move away from the rock because the dorsal horn has already sent that message. If your brain is the bodys CEO, then the spinal cord is middle management.
Optogenetic Studies Of Brain Regions Involved In Pain
Recently we have applied an optogenetic approach to explore novel brain regions involved in opiate analgesia. Opioids are important clinically, however their use is limited through the development of tolerance and addiction . Understanding the brain regions and cell types involved in these processes are is important to help tackle the problem. We had previously demonstrated that regulator of G protein signaling 9-2 is a negative modulator of morphine tolerance . In our recent study we demonstrated a potent role of Rgs9-2 in the nucleus accumbens in modulation of morphine tolerance. Taking advantage of an optogenetic strategy, we have showed that activation of Rgs9 expressing neurons in the NAc leads to the rapid development of analgesic tolerance in the hot plate test . Using bacterial artificial chromosome lines expressing Cre recombinase, we were also able to selectively stimulate the two main NAc neuronal subpopulations: those expressing primarily D1 dopamine receptors and those enriched in D2 dopamine receptors . Activation of channelrhodopsin-2 in each of these neuronal subpopulation demonstrated that morphine tolerance is modulated by D1 type neurons, which is the population that mostly expresses mu opioid receptors . In accord with our earlier findings on a role of Rgs9-2 in the NAc in morphine tolerance, activation of D1-type but not D2-type neurons increases Rgs9-2 levels in the NAc .
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