Somatosensory, Pain, Plasticity, and PNS Nerve Injury Flashcards

Vocabulary-style flashcards based on lecture notes covering proprioceptors, cutaneous receptors, pain systems, neurological plasticity, nerve injury types, and neuromuscular junction diseases.

Muscle spindle

The most structurally complex proprioceptor that detects absolute muscle length, change in muscle length, rate of change in length, and stretch.

Dynamic bag fibers

Fibers within the muscle spindle that detect the rate of change in muscle length.

Static bag fibers

Fibers within the muscle spindle that detect muscle length.

Nuclear chain fibers

Fibers within the muscle spindle that primarily signal muscle length.

Primary ending (annulospiral ending)

A sensory ending that wraps around both bag and chain fibers and detects both muscle length and the rate of change of length.

Secondary (flower-spray) ending

A sensory ending that innervates nuclear chain fibers and detects length and tension.

Afferent fiber $Ia$

The fiber that innervates the primary spindle ending.

Afferent fiber $II$

The fiber that innervates the secondary spindle ending.

Golgi tendon organ

A receptor located at the musculotendinous junction that detects muscle tension.

Afferent fiber $Ib$

The fiber that innervates the Golgi tendon organ.

Meissner corpuscle

A rapidly adapting cutaneous receptor that detects light touch and low-frequency vibration.

Merkel disk

A slowly adapting cutaneous receptor that detects pressure.

Pacinian corpuscle

A rapidly adapting cutaneous receptor that detects vibration and has the lowest threshold (highest sensitivity).

Ruffini corpuscle

A slowly adapting cutaneous receptor that detects skin stretch.

ALS (Anterolateral System)

The sensory pathway that carries pain and temperature.

$A-\delta$ fibers

Fibers that produce fast, sharp, and localized pain.

$C$ fibers

Fibers that produce slow, dull, aching pain and have an emotional/affective component.

Mechanonociceptors

One of the four major nociceptor types specializing in mechanical pain.

Thermonociceptors

One of the four major nociceptor types specializing in thermal stimuli.

Chemonociceptors

One of the four major nociceptor types specializing in chemical stimuli.

Polymodal nociceptors

One of the four major nociceptor types that respond to multiple modes of painful stimuli.

Hyperalgesia

An increased sensitivity to painful stimuli.

Allodynia

Pain resulting from a normally nonpainful stimulus.

Paresthesia

An abnormal sensation such as tingling, burning, or prickling.

Gate Control Theory

The theory stating that stimulation of non-nociceptive fibers can inhibit pain fibers.

Enkephalin

An endogenous opioid that mediates Gate Control Theory and decreases the release of Substance P.

Substance P

A neurotransmitter released by primary pain afferents that contributes to sensitization.

Periaqueductal Gray (PAG)

A structure that, when activated, stimulates the Raphe nucleus.

Raphe nucleus

A nucleus that releases serotonin for pain modulation.

Locus ceruleus

A structure that releases norepinephrine for pain modulation.

Habituation

A decreased response after repeated stimulation.

Denervation hypersensitivity

The formation of new postsynaptic receptors following axon loss.

Synaptic hypereffectiveness

A process where remaining axons release more neurotransmitter after neighboring axons degenerate.

Silent synapses

Existing synapses that are normally unused.

Nudo's monkey study

A study showing that early training promotes cortical reorganization and recovery.

Kozlowski's study

A study indicating that immediate forced use may worsen injury.

Wallerian degeneration

The degeneration of the distal axon after injury, beginning $3-5$ days post-injury.

Chromatolysis

The swelling of the neuron cell body and nucleus following injury.

Axonal regeneration rate

The typical rate at which axons regrow, approximately $1-2\,mm/day$.

Schwann cells

Cells that promote regeneration in the Peripheral Nervous System (PNS).

Neuropraxia

A nerve injury involving damage to the myelin only, with no Wallerian degeneration.

Axonotmesis

A nerve injury where the axon is damaged but connective tissue remains intact, resulting in Wallerian degeneration.

Neurotmesis

Complete nerve severance, which associated with the poorest prognosis.

Myasthenia gravis

A neuromuscular junction disorder that attacks postsynaptic acetylcholine (ACh) receptors, where symptoms worsen with activity.

Lambert-Eaton

A neuromuscular junction disorder that attacks presynaptic voltage-gated calcium channels, where symptoms improve with activity.