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Questions and Answers
Which type of stimulus does not elicit fast pain?
Which type of stimulus does not elicit fast pain?
Which of the following substances does not directly stimulate nociceptors but rather increases their sensitivity?
Which of the following substances does not directly stimulate nociceptors but rather increases their sensitivity?
How does the rate of tissue damage relate to pain, particularly from heat?
How does the rate of tissue damage relate to pain, particularly from heat?
In the context of a tissue ischemia, which of these factors contributes most rapidly to pain?
In the context of a tissue ischemia, which of these factors contributes most rapidly to pain?
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Which neurotransmitter is primarily used by Aδ fibers when communicating fast pain to the spinal cord?
Which neurotransmitter is primarily used by Aδ fibers when communicating fast pain to the spinal cord?
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According to the International Association for the Study of Pain (IASP), what is the defining characteristic of pain?
According to the International Association for the Study of Pain (IASP), what is the defining characteristic of pain?
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What is the primary function of pain as a protective mechanism?
What is the primary function of pain as a protective mechanism?
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Which of the following is a characteristic of fast pain?
Which of the following is a characteristic of fast pain?
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Which type of nerve fiber is primarily responsible for transmitting slow pain signals?
Which type of nerve fiber is primarily responsible for transmitting slow pain signals?
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In which specific area are pain receptors NOT typically found?
In which specific area are pain receptors NOT typically found?
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Study Notes
Pain Perception
- Pain is an unpleasant sensory and emotional experience.
- Nociceptors are receptors stimulated by potentially tissue damaging stimuli.
- Pain is a symptom, subjective, protective, and modified by developmental, behavioral, personality and cultural factors.
- Pain can be acute or chronic.
Types of Pain
- Fast pain: Also called sharp, pricking, acute pain, felt within 0.1 seconds after the stimulus is applied. Well localized. Not felt in deeper tissues.
- Slow pain: Also called slow burning, aching, throbbing, nauseous, chronic pain. Felt after 1 second or more, increasing over time. Poorly localized, often associated with tissue destruction, and can lead to prolonged, almost unbearable suffering.
Nerve Fibers
- Different nerve fibers transmit pain signals, categorized by myelination, diameter, and speed.
- A delta fibers are fast pain fibers and myelinated thin nerves associated with sharp, localized pain.
- C fibers are slow pain fibers, unmyelinated, associated with dull, poorly localized lingering pain.
Pain Receptors and Stimulation
- Pain receptors are free nerve endings.
- Located in superficial skin layers, somatic tissues, and some internal tissues (excluding brain and lung parenchyma).
- Stimulated by mechanical, thermal, and chemical factors.
- Fast pain is elicited by mechanical or thermal stimuli.
- Slow pain is triggered by all three types of stimuli.
Neurotransmitters
- Chemicals (e.g. bradykinin, histamine, serotonin, K+ ions) released cause pain and sensitize nociceptors.
- Prostaglandins and substance P increase sensitivity, without directly stimulating nociceptors.
Pain Receptors and their Stimulation
- Pain receptors are free nerve endings.
- Widespread in superficial skin and somatic tissues.
- Stimuli include mechanical, thermal, and chemical.
- Chemicals like bradykinin, serotonin, K+ ions, histamine, H+, lactic acids, ACh, proteolytic enzymes, leucotrienes, cytokines & capsaicin.
Pain Modulation
- Pain perception is variable due to endogenous & exogenous mechanisms, which can increase or decrease pain threshold.
- Enhancement and inhibition occur at all nervous system levels.
- Modulation at nerve, spinal cord and brain levels influence pain perception.
Pain Suppression (Pain Modulation)
- Includes periaqueductal gray and periventricular areas of the mesencephalon and pons, raphe magnus nucleus, as well as a pain inhibitory complex in the spinal cord's dorsal horns.
- Transmitters like enkephalin (pre- and post-synaptically inhibit pain fibers - Aδ,C) and serotonin (which stimulates enkephalin release).
- Brain opioid system: endorphins (hypothalamus/pituitary), enkephalins and dynorphins (brain stem).
Opioid Actions
- Endogenous opioid peptides, such as endorphin, enkephalin, and dynorphin, and exogenous substances like morphine, codeine, fentanyl, pethidine and heroin.
- Act presynaptically or postsynaptically to block calcium channels, inhibiting neurotransmitter release (e.g. glutamate, substance P) and trigger potassium channel opening, resulting in membrane hyperpolarization and inhibiting pain neurotransmitter activity.
- Activate descending pain modulatory inhibitory pathway and inhibit GABA-mediated inhibition of descending pathways.
Gate Control Theory
- Non-painful input closes gates to painful input.
- This occurs at the substantia gelatinosa in the dorsal horn of the spinal cord, and stimulation in the Aδ or C neurons will activate it.
- Stimulation of Aβ fibers opens the gates.
- The theory helps explain methods of pain relief through massage, applying irritants, transcutaneous electrical stimulation and acupuncture.
Varieties of Pain
- Phantom pain: occurs when there's no stimulus but a feeling of pain in the missing limb/tissue.
- Psychogenic pain: originates from emotional or psychological factors.
- Neuropathic pain: a pain caused by damage or disease to the somatosensory nervous system.
Pain in Dentistry
- Pulpal Origin: Visceral pain; threshold type pain. responds to various stimuli, but not usually mastication.
- PDL Origin: Deep somatic musculoskeletal pain. more localized than pulpal pain, is related to biomechanical function & can be precisely localized.
- A-delta fibers and C-fibers contribute to pain sensations from different parts of the mouth and teeth.
Orofacial Pain Pathway
- Somatic inputs from facial structures travel through the trigeminal nerve (CN V) to various brain nuclei.
- Different nerves transmit sensations in the face and mouth directly to specific central nervous system nuclei.
Orthodontic Pain Pathway
- The trigeminal neurons receive nociceptive signals.
- These first-order neurons synapse with second-order neurons in the trigeminal nucleus caudalis, which then decussate (cross to the opposite side) before synapsing with third-order neurons in the thalamus.
- The thalamus then relays the signals to the somatosensory cortex where the pain perception is integrated.
Dental Pain of Pulpal Origin
- Characterized by visceral pain, threshold, and widespread stimuli response.
- Non-localized and doesn't always persist.
- Can become chronic or spread to the periodontal ligament.
Dental Pain of PDL Origin
- Deeper somatic musculoskeletal pain.
- More localized than pulpal pain.
- Intimately related to biomechanical function (e.g. mastication).
- Highly localized & related to biting pressure or discomfort localized to a specific area.
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Description
This quiz delves into the complexities of pain perception, exploring various types of pain including fast and slow pain, along with the nerve fibers involved in transmitting pain signals. Understand the differences between acute and chronic pain and how various factors can affect it.
