Physiology of Nociception

<p>In the setting of continuous damage or inflammation (A)</p> Signup and view all the answers

<p>0.5 – 2 m/sec (A)</p> Signup and view all the answers

<p>C fibers (B)</p> Signup and view all the answers

<p>Fast pain (B)</p> Signup and view all the answers

<p>Thalamic nuclei (A)</p> Signup and view all the answers

<p>Release of enkephalins (C)</p> Signup and view all the answers

<p>Visceral pain (B)</p> Signup and view all the answers

<p>Mu opioid receptors (D)</p> Signup and view all the answers

<p>Fast pain (C)</p> Signup and view all the answers

<p>Often described as sharp or burning (B)</p> Signup and view all the answers

<p>Mechanical nociceptors (C)</p> Signup and view all the answers

<p>Skeletal muscle (C)</p> Signup and view all the answers

<p>Visceral pain (B)</p> Signup and view all the answers

<p>Usually described as sharp (A)</p> Signup and view all the answers

<p>Amygdala, cingulate gyrus, insular cortex (B)</p> Signup and view all the answers

<p>Serotonin and norepinephrine (A)</p> Signup and view all the answers

<p>Referred pain is often confused with visceral pain (D)</p> Signup and view all the answers

<p>Because it is confused with visceral pain (C)</p> Signup and view all the answers

<p>C fibers (C)</p> Signup and view all the answers

<p>It is released by C fibers and causes long-lasting depolarization of projection neurons. (D)</p> Signup and view all the answers

<p>Nerve injury reduces the stimulation of inhibitory interneurons, leading to excessive activation of excitatory interneurons and nociceptive projection neurons. (D)</p> Signup and view all the answers

<p>A-beta fibers stimulate inhibitory interneurons, reducing the transmission of pain from projection interneurons. (A)</p> Signup and view all the answers

<p>A-delta fibers transmit fast, sharp pain, while C fibers transmit slow, dull pain. (B)</p> Signup and view all the answers

<p>Neospinothalamic pathway (C)</p> Signup and view all the answers

<p>Referred pain occurs when pain is perceived in an area different from the site of injury or inflammation. (B)</p> Signup and view all the answers

C fibers are responsible for transmitting slow, poorly localized pain and itching sensations. They are unmyelinated and have a slow conduction velocity.

Polymodal nociceptors respond to multiple stimuli, including high-intensity mechanical, chemical, or thermal stimuli. This means they can be activated by various types of damage.

A-delta fibers are responsible for transmitting sharp, well-localized pain. They are myelinated and have a faster conduction velocity.

Silent nociceptors are normally inactive but can be 'awakened' to transmit pain information in the setting of continuous tissue damage or inflammation. This suggests a role in chronic pain.

C fibers have a conduction velocity between 0.5 and 2 meters per second. This slow speed explains why the pain they transmit is perceived as delayed and persistent.

C fibers are the primary type of fiber responsible for transmitting thermoception (temperature) sensations. This means they detect both hot and cold temperatures.

A-delta fibers carry fast pain, which is perceived as sharp and well-localized. It is the immediate pain response to injury.

The paleospinothalamic pathway carries signals to the thalamic nuclei. This pathway is associated with slow, poorly localized pain.

Projection neurons in the spinal cord are likely inhibited by the release of enkephalins. This is a mechanism of pain suppression by the body.

Visceral pain is likely transmitted along the anterior spinothalamic tract. It is characterized by dull, deep pain.

Mu opioid receptors, when activated, bring the most relief from pain. They are highly concentrated on C-fibers, suggesting a role in reducing the slow, dull pain.

Fast pain, unlike other sensory modalities, does not exhibit adaptation. This means that the pain signal remains constant, even with prolonged stimulation.

Dermal pain is often described as sharp or burning. This is due to the activation of nociceptors in the skin.

Mechanical nociceptors are activated by intense pressure applied to a structure. They are sensitive to strong squeezing or stretching.

Dull, pressure-like pain is common in skeletal muscle. This type of pain often results from overuse or strain.

Visceral pain can be described as dull, cramping, but can also be sharp. It is often associated with internal organs.

Pain from mesothelial linings, such as those lining the chest cavity, is usually described as sharp. This is due to the sensitivity of these tissues.

The amygdala, cingulate gyrus, and insular cortex are CNS areas involved in both pain perception and emotional processing. This links pain to mood and stress responses.

The serotonin and norepinephrine areas in the midbrain are involved in both descending modulation of pain and the pathophysiology of depression. This complex connection highlights the interplay between pain and mood disorders.

Referred pain is different from superficial skin nociception because it is perceived as a more internal pain, often confused with pain originating from visceral organs.

Referred pain is considered 'mixed message' pain because it is confused with visceral pain. This can lead to misdiagnosis and inappropriate treatment.

C fibers extend from the heart to areas like T1-T2, causing referred pain to the inner side of the arm. This explains why heart attacks can sometimes be felt in the arm.

Substance P is released by C fibers and causes long-lasting depolarization of projection neurons. This contributes to the perception of persistent, burning pain.

Nerve injury can sometimes cause neuropathic pain instead of analgesia because it disrupts the normal balance of excitatory and inhibitory neurons. This leads to excessive neuronal activity and chronic pain.

A-beta fibers stimulate inhibitory interneurons, reducing the transmission of pain from projection interneurons. This is a key mechanism in the pain gate theory.

A-delta fibers transmit fast, sharp pain, while C fibers transmit slow, dull pain. This difference is due to their different structures and conduction velocities.

The neospinothalamic pathway is associated with the transmission of fast, sharp pain. It projects to the thalamus and then to the somatosensory cortex.

Referred pain occurs when pain is perceived in an area different from the site of injury or inflammation. This can be confusing and misleading.