Pain Function and Classification Lecture Notes

Comprehensive flashcards covering the definition, classification, physiology, and modulation of pain based on lecture notes.

Pain

An unpleasant sensory and emotional experience associated with actual or potential tissue damage according to the International Association for the Study of Pain.

Sensory component of pain

The physical detection of a pain stimulus.

Motivationally-affective component of pain

An uncontrollable emotional reaction that drives activity toward ending the pain sensation.

Superficial pain

Pain occurring on the body surface.

Deep Somatic pain

Pain originating from muscles or connective tissues.

Visceral pain

Pain originating from internal organs, where nociceptors are the only source of sensation.

Acute pain

Short-term pain ($< 6 \text{ months}$) that is reversible and primarily caused by direct stimulation of nociceptors.

Chronic pain

Long-term pain ($> 6 \text{ months}$) where psychological and behavioral factors play a major role, and the pain itself may become a disease.

Pain Stimulus

Triggered by tissue damage from intense mechanical deformation, extreme temperatures, or chemicals like $H^+$, histamine, and prostaglandins.

Nociceptors

Free nerve endings in the epidermis and internal tissues (except the brain) that adapt poorly and detect potential or actual tissue damage.

High-threshold mechanoreceptors

A type of nociceptor that detects intense mechanical pressure.

Polymodal receptors

Nociceptors that respond to high-intensity mechanical, thermal, and chemical stimuli.

Fast Pain (First Pain)

A sharp, prickling, well-localized sensation conducted by lightly myelinated $A\text{-delta}$ fibers via the Spinothalamic tract.

Slow Pain (Second Pain)

A dull, burning, diffuse, and persistent sensation conducted by unmyelinated $C \text{ fibers}$ via the Spinoreticular tract.

Referred Pain

Visceral pain perceived as coming from a different body part (usually the skin) because sensory impulses from both areas travel the same nerve pathway.

Head's Zones

Specific segmental fields of the skin to which pain from specific internal organs is characteristically referred.

Anterolateral System

The system responsible for transmitting pain information to the brain, consisting of the Spinothalamic, Spinoreticular, and Spinomesencephalic tracts.

Spinothalamic Tract

The main pathway signaling pain to the somatosensory cortex for conscious perception and localization.

Spinoreticular Tract

A pathway projecting to the nonspecific thalamus and cortex that is involved in the emotional and motivational aspects of pain.

Spinomesencephalic Tract

A pathway projecting to the periaqueductal grey of the midbrain that signals the limbic system and Autonomic Nervous System (ANS).

Trigeminothalamic System

Conveys pain from the head, face, and oral cavity via the trigeminal nerve to the VPM nucleus of the thalamus.

Segmental Inhibition

Pain suppression occurring at the spinal cord level where transmission between the first and second neurons is inhibited.

Descending Inhibition

Pain suppression where higher brain centers send signals down to block pain relay before it reaches the brain.

Endogenous Opioid System

The body's internal painkiller system consisting of amino acid sequences like Enkephalins, Dynorphins, and Endorphins.

$$\beta\text{-endorphin}$$

The most potent substance within the body's endogenous opioid system.