The Non Visual Sensory Systems PAIN Nearly everyone experiences pain and this is good Pain is a warning signal It lets us know if something is wrong Can also be a function or cause of depression or drug dependency There are many reasons someone might experience pain Three different kinds of pain Cutaneous pain arises from a superficial structure like a paper cut There is also deep somatic pain This typically involves muscles tendons or joints like a sprained ankle The actual focal point of a deep somatic pain is more difficult to pinpoint than cutaneous pain because it tends to radiate out Finally there is visceral pain Visceral pain originates in the viscera This is the cell lining that surrounds many of one s internal organs Visceral pain is not caused by actual tissue damage but rather by a stretching or distension of viscera Pain is subjective What really hurts one person may be meh to another It can be genetics neurophysiology or psychological for why this is Not everyone experiences pain CIPA is a disorder where someone doesn t experience pain They are born with an inability to feel pain This is incredibly dangerous They must be observed 24 7 Walking across heated pavement or stepping on a rusted nail are things they can t feel They can feel textures and certain stimuli but they can t feel pain If a certain touch becomes painful then they can t feel it CIPA is caused by a peripheral nerve defect where pain is not transmitted A lot of our responses to pain are learned Depends on social modeling looking at the reactions of others and how they respond Some people have an insensitivity to the subjective proponent of pain There is a very strong emotional component to pain If one doesn t respond emotionally to pain it won t hurt very badly There are some drugs that can block this component Pain can be either acute or chronic Acute lasts during the injury chronic means it lasts long after the injury is healed The process of receiving pain is nociception It is possible to have pain without nociception like in phantom limb pain You can also have nociception without pain It s much easier to say where pain receptors are not because there are a lot of them They are not in bones or the brain they are not in lung tissue and not in the non living parts of teeth hair and nails Pain receptors are very generally one of two types A delta and C fibers Couple of neurotransmitters important for transmitting pain If mild pain glutamate is important If pain is severe it s glutamate and substance P that are important There are both fast and slow components of pain Shutting the door of a car on a finger get an immediate sharp pain and then a dull throbbing pain The immediate sharp bright pain is the fast pain and that involves A delta fibers These fibers are necessary for transmission of fast pain The C fibers are responsible for slower dull throbbing pain Stimuli is picked up by the receptors sent to spinal cord goes to the brain stem hits the thalamus and then one gets the basic sensation of pain Information then goes to somatosensory cortex it s here that one gets precision and determination where exactly and what exactly It goes from ow my ankle hurts to crap my ankle hurts and there s a piece of glass in it One also gets offshoots to the limbic system this is where the emotional component of pain is registered the affective component of pain At the site of the injury there are the release of all kinds of chemicals that will amplify that pain There are other reactions like clenching teeth and drawing back Some receptors respond to intense heat that registers pain Heat receptors respond to a chemical that is incredibly common in this part of the country This is in hot peppers called capsaicin This will cause an immediate dumping of neurotransmitters in the localized pain receptors Once all the neurotransmitters are gone there is numbness Acts locally Can be used on sore joints to numb pain The gate theory of pain explains some of pain but not all of it The pain receptors have synapses in the spinal cord The T cells in the spinal cord receive all of this information The idea of the gate theory is that the T cells are receiving this information to be sent up they receive all kinds of information It is possible to put a block on the painful information sent up to the brain if one over stimulates the T cells with other tactile information One uses the gate theory pretty often in everyday life Like rubbing the elbow if the funny bone is hit Sends other tactile information that hopefully blocks the information sent by T cells We have our bodies own pain killers that inhibit or decrease pain Endorphins and enkephalins help The PAG is where one finds a lot of opiate receptors A lot of things can cause the release of these endorphins and enkephalins Really liking things like chocolate and or music can cause the release of these chemicals These chemicals all play a role in the so called placebo responses If the individual is told they will receive a really painful stimulus and is then given a mild shock they will report a much more violent pain It s possible to become sensitized to pain That s because of chemicals that are released will actually increase the number of sodium channels on nearby neurons that are likely to fire So things that are normally not painful suddenly are Pain and itch are two different sensations Pain inhibits itch and vice versa Itch has its own spinal pathway uses its own neurotransmitter gastrin releasing peptide TASTE There are certain things that let us know if something is good to eat or not There is something called learned taste aversion that we experience With the learned taste aversion experiment there are two groups of rats They re given water On test day we give them a novel substance that they ve never had before sugar water The rats are going to exhibit something called neophobia fear of something new Humans have the same thing Following sugar water the experimental group is injected with a drug that makes them nauseous the control group is injected with saline On the next test day they re again exposed to sugar water The control group will drink that sugar water the experimental group will not touch that water because they have developed a learned taste aversion Learned taste aversion is critical for animals that can t throw up They ll eat a little of something see what happens and then decide whether or not to eat it in the future depending on their reaction When