Pain

Question 1

What is nociception?

Answer 1

The sensory process that detects harmful or potentially harmful stimuli, leading to the perception of pain.

Question 2

What are nociceptors?

Answer 2

Specialized sensory neurons that respond to noxious stimuli, such as mechanical, thermal, or chemical signals.

Question 3

What types of fibers are involved in nociceptive signaling?

Answer 3

• Aδ fibers: Fast-conducting, myelinated fibers responsible for sharp, localized pain.
• C fibers: Slow-conducting, unmyelinated fibers responsible for dull, aching, and burning pain.

Question 4

What is the role of the dorsal horn in nociception?

Answer 4

It is the site in the spinal cord where nociceptive signals are transmitted to second-order neurons.

Question 5

Name the four main stages of nociception.

Answer 5

1. Transduction: Conversion of noxious stimuli into electrical signals by nociceptors.
2. Transmission: Propagation of signals through the nervous system.
3. Perception: Conscious experience of pain in the brain.
4. Modulation: Modification of pain signals by descending pathways.

Question 6

What is the spinothalamic tract’s role in nociception?

Answer 6

It transmits nociceptive information from the spinal cord to the thalamus, and then to the somatosensory cortex for pain perception.

Question 7

Which chemical mediators activate nociceptors?

Answer 7

• Bradykinin: Released during tissue injury, sensitizes nociceptors.
• Prostaglandins: Increase sensitivity to pain.
• Substance P: Enhances pain signaling in the spinal cord.

Question 8

What is the role of glutamate in nociception?

Answer 8

Glutamate is a primary excitatory neurotransmitter in nociceptive pathways, acting on AMPA and NMDA receptors.

Question 9

How does the gate control theory explain pain modulation?

Answer 9

Non-noxious input (e.g., from Aβ fibers) can inhibit nociceptive signals at the dorsal horn, “closing the gate” to pain perception.

Question 10

What is the role of descending pathways in pain modulation?

Answer 10

Descending pathways from the brainstem release inhibitory neurotransmitters (e.g., serotonin, norepinephrine, endorphins) to reduce pain signals.

Question 11

What is the difference between nociceptive and neuropathic pain?

Answer 11

• Nociceptive pain: Results from actual or potential tissue damage.
• Neuropathic pain: Caused by damage or dysfunction of the nervous system.

Question 12

What is referred pain?

Answer 12

Pain perceived in a location different from the site of the actual stimulus, often due to convergence of visceral and somatic afferents.

Question 13

How do NSAIDs modulate nociception?

Answer 13

They inhibit cyclooxygenase (COX) enzymes, reducing prostaglandin synthesis and decreasing nociceptor sensitization.

Question 14

What is the mechanism of opioids in pain modulation?

Answer 14

Opioids bind to mu-opioid receptors, inhibiting neurotransmitter release and enhancing descending inhibitory pathways.

Question 15

How does capsaicin reduce nociception?

Answer 15

Activates TRPV1 receptors, causing calcium influx and desensitization of nociceptive neurons.

Question 16

What is allodynia?

Answer 16

Pain due to a stimulus that does not normally provoke pain, often seen in neuropathic conditions.

Question 17

What is hyperalgesia?

Answer 17

An exaggerated pain response to a normally painful stimulus, often due to sensitization of nociceptors or central neurons.

Question 18

What is the role of local anesthetics in nociception?

Answer 18

Block voltage-gated sodium channels, preventing the generation and propagation of nociceptive signals.

Question 19

How do antidepressants help in managing chronic pain

Answer 19

Enhance descending inhibitory pathways by increasing serotonin and norepinephrine availability in the CNS.

Question 20

What is central sensitization?

Answer 20

Increased excitability of neurons in the central nervous system, leading to amplified pain perception, often associated with chronic pain.

Question 21

What are the main types of nociceptors based on modality?

Answer 21

• Mechanical nociceptors: Respond to mechanical damage like cuts or pressure.
• Thermal nociceptors: Respond to extreme temperatures.
• Chemical nociceptors: Detect irritating chemicals.
• Polymodal nociceptors: Respond to multiple types of stimuli (mechanical, thermal, and chemical).

Question 22

What is the difference between silent and active nociceptors?

Answer 22

• Active nociceptors: Respond immediately to harmful stimuli.
• Silent nociceptors: Usually inactive but become responsive in the presence of inflammation.

Question 23

Which ion channels are involved in nociceptor activation?

Answer 23

TRPV1 (heat), TRPA1 (cold and irritants), ASIC (acid sensing), and voltage-gated sodium channels (signal propagation).

Question 24

What is peripheral sensitization?

Answer 24

Increased sensitivity of nociceptors to stimuli, often due to inflammatory mediators like prostaglandins or bradykinin.

Question 25

How do prostaglandins enhance nociceptor sensitivity?

Answer 25

They lower the activation threshold of nociceptors by modulating ion channels, amplifying the pain response.

Question 26

What is central sensitization?

Answer 26

Increased excitability of neurons in the dorsal horn of the spinal cord, leading to heightened pain perception.

Question 27

Name a condition where central sensitization is common.

Answer 27

Fibromyalgia, chronic pain syndromes.

Question 28

What are the two main ascending pathways for nociceptive signals?

Answer 28

1. Spinothalamic tract: Conveys pain and temperature to the thalamus and somatosensory cortex. 2. Spinoreticular tract: Sends signals to the reticular formation, influencing emotional and arousal aspects of pain.

Question 29

What is the role of endorphins in pain modulation?

Answer 29

Endorphins bind to opioid receptors to inhibit pain signals in the central nervous system.

Question 30

How do descending inhibitory pathways reduce pain?

Answer 30

By releasing neurotransmitters like serotonin and norepinephrine, which suppress nociceptive transmission at the spinal cord

Question 31

What is the difference between peripheral and central neuropathic pain?

Answer 31

Peripheral neuropathic pain arises from damage to peripheral nerves, while central neuropathic pain results from lesions or dysfunctions in the central nervous system.