19 Questions
What is the primary function of analgesics?
To reduce distress associated with pain
What type of pain is characterized by an aberration of the normal physiological pathway?
Chronic pain
Which type of nerve fibre is responsible for conveying sharp, well-localized pain?
Aδ fibres
What is the result of the activation of nociceptive neurons?
Depolarization of peripheral nerves
What is the primary difference between nociception and pain?
Pain is a subjective experience, while nociception is a direct response to tissue damage
What is the primary mechanism by which opioids produce analgesia?
Binding to opioid receptors in the central nervous system
What type of receptors are opioid receptors classified as?
G-protein coupled receptors
What is characterized by the requirement of increasingly higher doses of a drug to produce a given pharmacological effect?
Tolerance
What is the term for the withdrawal symptoms that occur when an individual stops taking an opioid drug?
Physical dependence
What type of pain is often resistant to conventional analgesics and is associated with neurological disease?
Neuropathic pain
Allodyria is a type of pain that is characterized by an intense and unpleasant sensation in response to an excessive noxious stimulus.
False
C fibres are myelinated nerve fibres that convey sharp, well-localized pain.
False
Bradykinin is a neurotransmitter that is involved in the inhibition of nociceptive neurons.
False
The dorsal horn is a structure in the peripheral nerve terminal where nociceptive neurons are activated.
False
The.rostroventral medulla is involved in descending inhibitory controls.
True
Enkephalins are found in the peripheral sensory neurons.
False
Opioid receptors are classified as Gs receptors.
False
Nausea and vomiting are associated with opioid use.
True
Neuropathic pain is typically responsive to conventional analgesics.
False
Study Notes
Pain and Analgesics
- Pain is a subjective experience, a direct response to an untoward event associated with tissue damage, and is characterized by nociception, the perception of noxious stimuli.
- Analgesics aim to reduce the distress associated with pain, not just its antinociceptive effects.
Types of Pain
- Acute pain: an intense and unpleasant sensation resulting from an excessive noxious stimulus.
- Chronic pain: aberrations of the normal physiological pathway, often accompanied by:
- Hyperalgesia: increased pain in response to a mild noxious stimulus.
- Allodyria: pain evoked by a non-noxious stimulus.
- Spontaneous pain: pain without an apparent stimulus.
Nociceptive Afferent Pathway
- Pain is transmitted through impulse activity in small-diameter primary afferent fibers of peripheral nerves, which have sensory endings.
- C fibers (unmyelinated) have polymodal nociceptive endings, conveying dull, diffuse, burning pain.
- Aδ fibers (myelinated) convey sharp, well-localized pain.
Modulation in the Nociceptive Pathway
- Transmission of pain to higher centers involves descending inhibitory controls, including:
- Amygdala
- Insular cortex
- Hypothalamus
- Periaqueductal grey
- Rostroventral medulla
- Substantia gelatinosa
Analgesic Drugs (Opioids)
- Opioids are derived from opium, an extract from poppy juice, and contain morphine.
- Opioid receptors include μ, δ, κ, and ORL, which are widely distributed in the brain, spinal cord, and peripheral sensory neurons.
- Endogenous ligands for opioid receptors include endorphins.
Mechanism of Action (Opioids)
- Opioids act on the CNS, producing:
- Analgesia
- Euphoria
- Respiratory depression
- Depression of the cough reflex
- Nausea and vomiting
- Pupillary constriction
- GI tract effects
- Other actions
Tolerance and Dependence
- Tolerance: increased dose required to produce a given pharmacological effect, partly due to desensitization of μ receptors.
- Physical dependence: withdrawal causes adverse physiological effects, such as irritability, aggression, shakes, and writhing.
Neuropathic Pain
- Neuropathic pain is associated with neurological disease, unrelated to peripheral tissue injury.
- It is often linked to conditions like stroke, multiple sclerosis, peripheral diabetic neuropathy, and shingles.
- Pathophysiology is poorly understood, and conventional analgesics may be ineffective, making it opioid-resistant.
Learn about the concept of pain, its perception, and the different types of pain. This quiz covers nociceptive pathways, endogenous modulation, and pharmacological modulation of pain, as well as analgesics and their effects.
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