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32 Cards in this Set
- Front
- Back
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Describe pain |
- protective mechanism meant to bring a conscious awareness of tissue being damaged is or is about to damage |
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What helps us avoid potentially harmful events in the future? |
Storage of painful experiences |
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Sensation of pain is accompanied by: |
1. motivated behavioural response: withdrawal of defense 2. emotional reaction: crying or fear 3. past or present experience: heightened pain |
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What are the types of pain? |
1. acute 2. chronic pain/neuropathic pain |
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Acute pain(3) |
- temporary and lasts less than 6 months - person experiences higher than normal level of anxiety - distress arises from pain but subsidizes as condition improves |
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Chronic pain/neuropathic pain (3) |
- characterized by repeated and intense episodes separated by periods without pain - presence of discomfort all the time but not related to disease - discomfort and pain becomes intense as condition worsen and warn about actual damage to body |
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Abnormal chronic pain can result from |
1. Damaged pathways in peripheral nerves or CNS 2. Abnormal signalling within the pain pathways in absence of peripheral injury or painful stimuli |
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Example of abnormal chronic pain |
neuropathic pain during stroke damage afferent pathways, leading to abnormal and persistent pain |
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3 categories of pain receptors |
1. mechanical nociceptors: respond to mechanical damage (cutting, pinching, crushing) 2. thermal nociceptors respond to temperature extremes 3. polymodal nociceptors respond to all kinds of damaging stimuli (irritating chemicals released from injured tissues) |
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Nociceptors do not have... |
specialized structure, posses naked nerve ending |
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Pain impulse travel: |
1. pain umpulses -> 2. nociceptors -> 3. A-deltra fibres OR C-fibres -> 4. CNS
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Fast pain pathways are called |
A-delta fibres |
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Pain impulses sent via A-delta fibres |
1. passes signals arising from mechanical and thermal nociceptors 2. these fibres are small and myelinated 3. transmit pain impulses are rate up to 6-30 met/sec |
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Ex of pain impulse sent via A-delta fibres
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pain from cut or burned fingers -> pain can be felt as twinge at first, followed by more diffuse, disagreeable, sharp and prickling sensatio |
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Slow pain pathways are called |
C-fibres |
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Pain impulses sent via C-fibres |
- carry impulses from polymodal nociceptors to CNA - are small, NON-mylinated fibres and carry impulses at a rate of 1-2 met/sec - feeling of pain is dull, unpleasant, aching, poorly localized and persists for longer time |
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Bradykinin ( this happens in C-fibre path)... |
- is activated by enzymes from injured tissue - stimulate polymodal receptor causing the long-lasting, aching pain that continues after removal of the mechanical or thermal stimulus |
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How do hot peppers activat the peripheral receptors of C-fibres? |
Capsaicin (from peppers) activates the peripheral receptors of C-fibres - this substance binds to both pain and thermal receptors causing burning sensation when eating hot peppers |
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Characteristics of fast pain (4) |
- occurs on stimulation of mechnical and thermal nociceptors - carried by small myelinated A-delta fibres - produces sharp, prickling sensation - easily localized - occurs FIRST |
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Characteristics of slow pain (5) |
- occurs on stimulation of polymodal nociceptors - carried by small, unmyelinated C-fibres - produces dull, aching, burning sensation - poorly localized - occurs SECOND - persists for longer time, more unpleasant |
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A-delta fibres: 1. general characteristics 2. speed 3. diameter 4. stimuli 5. description 6. receptor classification |
1. small and myelinated 2. 6-3m/sec 3. 1-5 um 4. fast pain,cold, warmth, mechanical 5. sharp, stabbing or acute 6. free nerve ending |
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C-fibre: 1. general characteristics 2. speed 3. diameter 4. stimuli 5. description 6. receptor classification |
1. small and UNmyelinated 2. <1-2m/sec 3. 0.5-2 um 4. slow pain, heat, cold, mechanical 5. burning, aching, throbbing 6. free nerve ending |
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List two pain neurotransmitters and briefly describe each |
1. Substance P: activates ascending pathways that transmit nociceptive signals to higher levels for further processing 2. Glutamate: major excitatory neurotransmitter |
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The brain has a built in analgesic system that: (2)
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1. supresses transmission in pain pathways as they enter spinal cord
2. depends on presence of opiate receptors (endogenous opiates: endorphins, enkephalins, dynorphin) |
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Will a person with am amputated limb continue to receive pain from that limb? |
WILL continue to receive a pain from amputated limb as pain sensation evoked in the brain is projected to the amputation
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Pathway of pain from amputated limb |
amputated limb -> irritation of severed nerve endings -> action potential -> afferent pathways -> somatosensory cortex -> interpreted as pain from missing limb
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What are dematomes? |
areas of the body that are served by a particular spinal nerve and its branches |
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Patient suffering from a myocardial infraction (MI) |
- may thin kthe pain is originating from his left arm when the sensory input is coming from the heart |
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Shared pathways of dematomes and internal organs are evident in |
referred pain |
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where does the perception of pain occur |
thalamus |
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glutamate binds with what 2 receptors on plasma membrane of dorsal horn? |
1. AMPA receptors (transmit pain msg to higher brain centers) 2. NMDA receptors ( do not involve pain transmission, bu Ca2+ initiates 2nd msngr sys. and contributes to exaggerated sensitivity of area to pain) |
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What are the 2 built-in pain suppressing systems? |
1. periaqueductal gray matter (electrical stimulation) 2. reticular formation (blocks release of sub. P) - they both release endogenous opiates |
