Lecture 21. Pain Receptors & Pain Pathways

What is pain as defined in neuroscience?

An unpleasant sensory and emotional experience associated with actual or potential tissue damage.

What is nociception?

The unconscious activity induced by a harmful stimulus applied to sensory receptors.

Define algesia.

Sensitivity to pain.

What is allodynia?

Sensation of pain in response to innocuous stimuli.

What does hyperalgesia refer to?

An exaggerated response to a noxious stimulus.

What is analgesia?

Absence of pain in response to stimulation which would normally be painful.

What fibers are responsible for fast pain detection?

Aδ fibers.

Which fibers contribute to slow pain detection?

C fibers.

What are the main types of pain categories?

First/Fast Pain and Second/Slow Pain.

What is the ascending spinothalamic pathway involved in?

Pain and temperature processing.

What neurotransmitter is primarily associated with nociceptors involved in fast pain?

Glutamate.

What neurotransmitter is associated with slow pain transmission?

Substance P.

What is peripheral sensitization?

Increased excitability of nociceptor terminals and lowered threshold for activation following tissue damage.

What role do NMDA receptors play in chronic pain?

They mediate excitability and contribute to central sensitization.

What kind of pain is phantom limb syndrome related to?

Neuropathic pain resulting from maladaptive plasticity.

What is referred pain?

Pain perceived from a remote somatic portion of the body wall originating from a visceral structure.

Describe the function of enkephalins in pain modulation.

They mediate pre- and post-synaptic inhibition of pain fibers, contributing to pain modulation.

What does the Gate Control Theory propose?

Non-painful input closes the gates to painful input, preventing pain sensation from traveling to the CNS.

What is the primary target of the descending pain pathways?

The dorsal horn of the spinal cord.

What happens in central sensitization?

Increased excitability of neurons in the dorsal horn of the spinal cord following high activity levels in nociceptive afferents.

How does the body suppress pain according to descending pathways?

Through an innate analgesia system involving the periaqueductal gray and the raphe nucleus.

What is the main challenge in treating phantom limb pain?

It can be difficult to treat with conventional analgesic medication.

What structures are involved in processing visceral pain?

Dorsal root ganglia and nucleus of solitary tract in the medulla.

What is a major consequence of visceral pain?

It is often diffuse and difficult to localize precisely.

What is the clinical relevance of understanding referred pain patterns?

Critical for diagnosis that could otherwise be missed.