1
Q
What is pain?
A
Pain is an unpleasant sensation (sensory and emotional) with biological, psychological, and social components. It can be classified by duration (acute, subacute, chronic).
2
Q
What is the function of pain?
A
- Alerts of a problem
- Protects the body from further injury
- Triggers withdrawal reflex
- Aids healing
3
Q
What are the main theories of pain?
A
- Direct ascend to the brain
- Neural specificity theory
- Pattern theory
- Gate control theory
- Neuromatrix theory
4
Q
What are nociceptors?
A
Peripheral receptors sensitive to mechanical or chemical stimuli. They are free nerve endings with small receptive fields, specific for pain, and do not adapt to repeated stimulation.
5
Q
What are the two types of nociception?
A
- First or Epicritic Pain: Sharp, pricking pain at the moment of injury; well-localized; high threshold for mechano-heat receptors; thinly myelinated A-delta fibers.
- Second or Protopathic Pain: Dull, aching pain lasting after the stimulus; polymodal nociceptors (chemical, thermal, mechanical); unmyelinated C fibers.
6
Q
What substances are involved in pain signaling?
A
- Prostaglandins
- Histamines
- Neuropeptides (Substance P, CGRP, glutamate, etc.)
- Neurotrophins (NGF, BDNF, etc.)
7
Q
What are the key receptors involved in pain?
A
- Neurotrophin receptors
- Tyrosine kinase receptors
- TRPV1, TRPV3
- Tachykinin receptors
- Purinergic receptors (ATP)
- Opioid and cannabinoid receptors
8
Q
Describe the pain pathway.
A
- First-order neuron: From peripheral nerve to thalamus (cell body in dorsal root ganglion).
- Second-order neuron: In dorsal horn of spinal cord; crosses midline and ascends via spinothalamic tract to thalamus.
- Third-order neuron: Projects to postcentral gyrus (via internal capsule).
9
Q
What is the anti-nociceptive system?
A
A system that modulates pain perception, involving:
- GABA
- Glycine
- Endorphins, enkephalins, dynorphins
- Opioid system (highest concentration in spinal cord laminae I and II)
10
Q
How is pain classified by duration?
A
- Acute: Recent onset, limited duration, identifiable cause.
- Chronic: Persists beyond healing time, often no clear cause.
11
Q
What is nociceptive pain?
A
Pain with intact signaling pathways; serves a protective function. Can be acute (physiologic) or chronic (pathologic).
12
Q
What is neuropathic pain?
A
Pain due to malfunction in the pain signaling pathway (central or peripheral). It serves no biological purpose and includes hyperalgesia and allodynia.
13
Q
What is visceral pain?
A
Pain from internal organs; poorly localized, accompanied by autonomic reflexes, and often referred to other locations.
14
Q
What is idiopathic pain?
A
Pain with no underlying lesion found despite investigation; disproportionate to tissue injury.
15
Q
What is psychogenic pain?
A
Pain primarily attributable to psychological factors without objective physical pathology.
16
Q
What is the OPQRST pain assessment?
A
- O: Onset
- P: Provoking/Palliating factors
- Q: Quality/Quantity
- R: Radiation
- S: Severity
- T: Timing
17
Q
What is the difference between pain threshold and pain tolerance?
A
- Pain threshold: Minimal stimulus required to produce pain (mediated by A-delta fibers).
- Pain tolerance: Greatest level of pain a subject can tolerate (mediated by C fibers).
18
Q
Why is pain treatment important?
A
- Reduces negative impact on the body
- Decreases complications and chronic pain risk
- Improves recovery, patient satisfaction, and quality of life
19
Q
What are the mechanisms of paracetamol (acetaminophen)?
A
- Acts mainly in the brain
- Weak COX-1/COX-2 inhibition
- Serotonergic pathway activation
- NMDA antagonism
- Metabolized by the liver; hepatotoxic in overdose
20
Q
What are the opioid receptor subtypes and their functions?
A
- Mu (μ): Analgesia, respiratory depression, euphoria, reduced GI motility.
- Delta (δ): Analgesia, antidepressant effects, modulates μ-receptor effects.
- Kappa (k): Analgesia, dysphoria, sedation, diuresis.
- Nociceptin receptor: Anxiety, depression, appetite modulation.
21
Q
What are the adverse effects of opioids?
A
- Respiratory depression
- Sedation
- Nausea/vomiting
- Constipation
22
Q
What are adjuvant medications for pain?
A
- Antidepressants
- Anticonvulsants
- Neuroleptics
- Antiarrhythmics
- Corticosteroids
- Osteoclast inhibitors
- Spasmolytics
- Alpha blockers/agonists
23
Q
What is the role of prostaglandins in pain?
A
Prostaglandins are responsible for pain throughout the body and are often released alongside histamines during inflammation.
24
Q
What is the spinothalamic pathway?
A
An ascending pathway that transmits pain signals from the body to the brain. It involves three neurons:
- First-order neuron (peripheral nerve to thalamus).
- Second-order neuron (spinal cord to thalamus).
- Third-order neuron (thalamus to postcentral gyrus).
25
What is the descending control of pain?
The brain modulates pain signals through descending pathways, such as the corticospinal tract, which can inhibit or enhance pain perception.
26
What is hyperalgesia?
An increased response to a normally painful stimulus, often seen in neuropathic pain.
27
What is allodynia?
A painful response to a normally non-painful stimulus, commonly associated with neuropathic pain.
28
What are the characteristics of visceral pain?
Not evoked from all viscera.
Poorly localized and diffuse.
Often referred to other locations.
Accompanied by autonomic reflexes.
29
What is the biological role of visceral nociceptors?
To warn of internal threats or disease, despite their low density compared to somatic afferents.
30
What is the pain threshold stimulus temperature?
44ºC is often used as the stimulus to measure pain threshold.
31
What is the submaximal effort tourniquet test?
A method to measure pain tolerance by inducing ischemic pain in a limb.
32
What are the consequences of poorly managed acute pain?
Increased risk of chronic pain.
Longer recovery times.
Higher healthcare costs.
Reduced patient satisfaction and quality of life.
33
What is the mechanism of NSAIDs?
NSAIDs inhibit cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis and inflammation. They are metabolized by the liver and excreted renally.
34
What is the pharmacokinetic advantage of diclofenac?
Diclofenac absorbs well in the bursae of joints, making it effective for localized pain.
35
What are pure opioid agonists?
Drugs that predominantly act on μ-receptors (e.g., morphine, fentanyl) and produce analgesia, euphoria, and respiratory depression.
36
What are agonist-antagonist opioids?
Drugs that act as agonists on some opioid receptors (e.g., kappa) and antagonists on others (e.g., mu), reducing the risk of respiratory depression.
37
What is the role of gabapentin in pain management?
Gabapentin produces opioid-sparing effects, improves postoperative pain scores, and is used for neuropathic pain.
38
What is pregabalin, and how does it differ from gabapentin?
Pregabalin has a similar mechanism to gabapentin but with a better pharmacokinetic profile. It is used for neuropathic pain and mixed results in postoperative pain.
39
What is ketamine's role in pain management?
Ketamine is an NMDA receptor antagonist used for acute and chronic pain, especially when opioids are ineffective or contraindicated.
40
What are the side effects of gabapentin and pregabalin?
Somnolence (drowsiness) and dizziness are common side effects.
41
What are the main neurotransmitters involved in nociception?
Neuropeptides (Substance P, CGRP).
Tachykinins.
Glutamate and aspartate.
Somatostatin.
Neurotrophins (NGF, BDNF).
42
What is the role of the opioid system in pain modulation?
The opioid system, particularly μ-receptors, plays a key role in analgesia, euphoria, and respiratory depression. It is concentrated in the spinal cord and brain.
43
What is the difference between nociceptive and neuropathic pain?
Nociceptive: Pain from intact signaling pathways; serves a protective function.
Neuropathic: Pain from malfunctioning signaling pathways; serves no biological purpose.
44
What is the role of the vagus nerve in nociception?
The vagus nerve does not have mechanical nociceptors but can transmit visceral pain signals.
45
What is the role of the neuromatrix theory in pain perception?
The neuromatrix theory suggests that pain is a multidimensional experience generated by neural networks in the brain, not just a direct response to stimuli.
46
What is the role of endorphins in pain control?
Endorphins are endogenous opioids that bind to opioid receptors, reducing pain perception and producing feelings of well-being.
47
What is the role of the gate control theory in pain modulation?
The gate control theory proposes that non-painful input (e.g., touch) can 'close the gate' and inhibit pain signals from reaching the brain.
48
What is the role of the pattern theory in pain perception?
The pattern theory suggests that pain is produced by the pattern of nerve impulses rather than specific pain receptors.
49
What is the role of the neural specificity theory in pain perception?
The neural specificity theory states that specific nerve fibers are dedicated to transmitting pain signals.
50
What is the role of the direct pathway theory in pain perception?
The direct pathway theory suggests that pain signals travel directly to the brain without modulation.
51
What is the role of the opioid receptor subtypes in pain modulation?
Mu (μ): Analgesia, respiratory depression, euphoria, reduced GI motility.
Delta (δ): Analgesia, antidepressant effects, modulates μ-receptor effects.
Kappa (k): Analgesia, dysphoria, sedation, diuresis.
Nociceptin receptor: Anxiety, depression, appetite modulation.
52
What is the role of the opioid system in the spinal cord?
The highest concentration of opioid receptors is found in the spinal cord, particularly around C-fiber terminal zones in laminae I and II, where they modulate pain signals.
53
What is the role of the periaqueductal gray (PAG) in pain modulation?
The PAG is a key brainstem region involved in descending pain control, releasing endogenous opioids to inhibit pain signals.
54
What is the role of the rostral ventromedial medulla (RVM) in pain modulation?
The RVM is part of the descending pain control system, modulating pain signals through excitatory and inhibitory pathways.
55
What is the role of the substantia gelatinosa in pain processing?
The substantia gelatinosa (lamina II of the spinal cord) is a key site for pain signal modulation, where opioids and other neurotransmitters act to reduce pain transmission.
56
What is the role of the thalamus in pain processing?
The thalamus acts as a relay station for pain signals, transmitting them to the cortex for perception and interpretation.
57
What is the role of the postcentral gyrus in pain perception?
The postcentral gyrus (primary somatosensory cortex) processes and localizes pain signals from the body.
58
What is the role of the internal capsule in pain pathways?
The internal capsule carries third-order neurons from the thalamus to the postcentral gyrus for pain perception.
59
What is the role of the corticospinal pathway in pain modulation?
The corticospinal pathway is a descending pathway that modulates pain signals by inhibiting or enhancing transmission in the spinal cord.
60
What is the role of GABA in pain modulation?
GABA is an inhibitory neurotransmitter that reduces pain signals by hyperpolarizing neurons in the spinal cord and brain.
61
What is the role of glycine in pain modulation?
Glycine is an inhibitory neurotransmitter in the spinal cord that reduces pain transmission by hyperpolarizing neurons.
62
What is the role of dynorphins in pain modulation?
Dynorphins are endogenous opioids that act on kappa receptors to produce analgesia and modulate pain signals.
63
What is the role of enkephalins in pain modulation?
Enkephalins are endogenous opioids that act on delta and mu receptors to produce analgesia and reduce pain transmission.
64
What is the role of the serotonergic pathway in pain modulation?
The serotonergic pathway, originating in the brainstem, modulates pain signals by inhibiting pain transmission in the spinal cord.
65
What is the role of the noradrenergic pathway in pain modulation?
The noradrenergic pathway, originating in the locus coeruleus, modulates pain signals by inhibiting pain transmission in the spinal cord.
66
What is the role of the NMDA receptor in pain processing?
The NMDA receptor is involved in central sensitization, amplifying pain signals and contributing to chronic pain states.
67
What is the role of the TRPV1 receptor in pain processing?
The TRPV1 receptor is activated by heat, capsaicin, and protons, playing a key role in thermal and inflammatory pain.
68
What is the role of the TRPV3 receptor in pain processing?
The TRPV3 receptor is activated by warm temperatures and contributes to thermal pain perception.
69
What is the role of the purinergic receptor in pain processing?
Purinergic receptors (e.g., P2X) are activated by ATP, playing a role in inflammatory and neuropathic pain.
70
What is the role of the cannabinoid receptor in pain modulation?
Cannabinoid receptors (CB1 and CB2) modulate pain signals by reducing neurotransmitter release and inflammation.
71
What is the role of the adenosine triphosphate (ATP) in pain signaling?
ATP activates purinergic receptors, contributing to pain signaling, especially in inflammatory and neuropathic pain.
72
What is the role of the tachykinin receptor in pain processing?
Tachykinin receptors (e.g., NK1) are activated by substance P, contributing to pain transmission and neurogenic inflammation.
73
What is the role of the tyrosine kinase receptor in pain processing?
Tyrosine kinase receptors are involved in neurotrophin signaling (e.g., NGF), contributing to pain sensitization and chronic pain.
74
What is the role of the neurotrophin receptor in pain processing?
Neurotrophin receptors (e.g., TrkA) are activated by NGF, contributing to pain sensitization and chronic pain states.
75
What is the role of the opioid receptor-like 1 (ORL1) receptor in pain modulation?
The ORL1 receptor (NOP) modulates pain signals and contributes to anxiety, depression, and tolerance to μ-agonists.
76
What is the role of the opioid receptor subtypes in respiratory depression?
Mu-2 receptors are primarily responsible for opioid-induced respiratory depression.
77
What is the role of the opioid receptor subtypes in euphoria?
Mu-1 receptors are primarily responsible for opioid-induced euphoria.
78
What is the role of the opioid receptor subtypes in constipation?
Mu-2 receptors are primarily responsible for opioid-induced reduced GI motility and constipation.
79
What is the role of the opioid receptor subtypes in diuresis?
Kappa receptors are primarily responsible for opioid-induced diuresis.
80
What is the role of the opioid receptor subtypes in dysphoria?
Kappa receptors are primarily responsible for opioid-induced dysphoria.
