NEUROSCIENCE: Glossary

GLOSSARY

Acuity:  Ability to distinguish fine detail or to localize precisely

Adaptation:  Decrease in sensory response when the stimulus is held constant

Afferent: Input to the cell body and dendrites (Note: In the PNS, afferent = sensory, but not necessarily so within the CNS)

Albinism:   Deficiency in or lack of ability to produce the pigment melanin. .

-algesia:   Suffix for pain, e.g. hyperalgesia: increased pain sensitivity; hypoalgesia: decreases pain sensitivity

-algia:   Suffix for pain

Algesiometer:   Device for generating a quantitative pain stimulus (also termed dolorimeter)

Allodynia:  Pain induced by an ordinarily nonpainful stimulus

Analgesia:  Loss or decrease of pain intensity

Ascending: Toward the cerebral cortex (in the context of CNS pathways)

Causalgia:   Burning pain associated with previous tissue injury (sympathetic dystrophy)

Contralateral:   Opposite side

Decussate:   Cross from one side (left or right) to the other side

Dermatome: Cutaneous receptive field of a spinal dorsal root

Descending: Away from the cerebral cortex (in the context of CNS pathways)

Efferent: Output from the cell body (Note: In the PNS, efferent = motor, but not necessarily so in the CNS)

-esthesia: Technical term for sensation, e.g. anesthesia: no sensation; paresthesia: abnormal or spontaneous (no external stimulus) sensation, such as "tingling"

Fibromyalgia:  Chronic pain originating from muscles and attachments which long outlasts the precipitating trigger event

Glabrous:  Having no hair

Graphesthesia: Recognition of a letter or number by tactile sensation

Ipsilateral:  Same side

Hyperpathia:   Combination of hyperalgesia and allodynia

Lemniscus:   Ribbon-shaped fiber tract

Neuralgia:   Pain that follows the course of a nerve or is related to a nerve;  e.g. trigeminal neuralgia

Lower motor neuron (LMN):   Neuron (a-motoneuron) directly innervating skeletal muscle cells (motor unit); cell body in the brainstem (head) or spinal cord ventral horn (lamina IX, rest of the body);  lesion results in flaccid paralysis, lack of muscle tone and reflexes, muscle atrophy, and (initially) muscle fasciculations (small, uncoordinated muscle fiber contractions)

Nociceptor:  Sensory ending responding to noxious stimuli and eliciting the sensation of pain

Noxious:   Damaging or potentially damaging to tissue

Otitis media:   Middle ear inflammation

Papilla:   Nipple

Paresis: Partial paralysis or weakness

Pruritus:  Itch

Receptive Field:  Normal region within which application of a stimulus elicits a response; appli8ed to neurons or groups of neurons in the peripheral or central nervous system

Sensitization:   Decreased threshold and/or increased response for a given stimulus due to increased sensitivity of the afferent ending

Sensory fiber types:  Sensory fibers are classified by diameter and conduction velocity:

Fiber Diameter, myelination Conduction
Group I 20-12 mm, myelinated 120-72 m/sec
Group II, Ab (A-beta) 12-6 mm, myelinated 72-36 m/sec
Group III,  Ad (A-delta) 6-1mm, myelinated 36-6 m/sec
Group IV, C <1mm, unmyelinated approx. 1 m/sec

Note:  I, II, III, IV from muscle & tendon;  Ab, Ad, C from skin & viscera

Somatic Sensory (Somatosensory): General sensory input widely distributed throughout the body; innervated by spinal afferents and General Somatic Afferent (GSA) cranial nerves (e.g. touch-pressure, hot-cold, pain)

Somatotopic:  Organization based on anatomical relations

Special Sensory: Sensory input mediated by complex structures located in the head; innervated by Special Sensory Afferent (SSA) cranial nerves (vision, hearing, taste, smell, equilibrium/vestibular)

Stereognosis: Recognition of the shape or identity of a stimulus based solely on touch

Transducer: Change of one form of energy to another form of energy or information

Two-point threshold: Smallest distance between adjacent stimuli that can be recognized as separate

Upper motor neuron (UMN):  Neuron originating in the motor cortex or brain stem which synapses directly on a-motoneurons (rare) or on local interneurons that synapse on a-motoneurons (most);  lesion typically results in spastic paralysis or paresis, increase muscle tone, increase reflex response (sometimes clonus, oscillating contraction following muscle stretch), Babinski sign

VPL, VPM:  Ventral-Posterior-Lateral and Ventral-Posterior-Medial nuclei of the thalamus; afferents from ascending sensory tracts (VPL from spinal sensory, VPM from trigeminal sensory); efferents to the cerebral cortex.