Which of the following carries fast pain?
Ans. a (Ad fibres) (Ref. Ganong 23rd/ Table 4-1; pg.167)# Fast pain is mediated by Ad fibers and causes sharp, localized sensation.0# Slow pain is mediated by C fibers and causes a dull, intense, diffuse, and unpleasant feeling.0PAIN# Pain impulses are transmitted via lightly myelinated Ad and unmyelinated C fibers.# Cold receptors are on dendritic endings of Ad fibers and C fibers, whereas heat receptors are on C fibers.0# Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage, whereas nociception is the unconscious activity induced by a harmful stimulus applied to sense receptors.# Acute pain has a sudden onset, recedes during the healing process, and serves as an important protective mechanism.# Chronic pain is persistent and caused by nerve damage; it is often refractory to NSAIDs and opiates.# Hyperalgesia is an exaggerated response to a noxious stimulus.# Allodynia is a sensation of pain in response to an innocuous stimulus.0# Referred pain is pain that originates in a visceral organ but is sensed at a somatic site. It may be due to convergence of somatic and visceral nociceptive afferent fibers on the same second-order neurons in the spinal dorsal horn that project to the thalamus and then to the somatosensory cortex.NERVE FIBER TYPES IN MAMMALIAN NERVE.Fiber TypeFunctionFiber Diameter (pm)Conduction Velocity (m/s)Spike Duration (ms)Absolute Refractory Period(ms)AAaProprioception; somatic motor12-2070-120_ AbTouch, pressure5-1230-700.4-0.50.4-1AgMotor to muscle spindles3-615-30--AdPain, cold, touch2-512-30--BCPreganglionic autonomic<33-151.21.2Dorsal rootPain, temperature, mechanorecepn0.4-1.20.5-222SympatheticPostganglionic sympathetic0.3-1.30.7--2.322Numerical Classification of Sensory Neurons.NumberOriginFiber TypeIaMuscle spindle, annulo-spiral endingAaIbGolgi tendon organAaIIMuscle spindle, flower-spray ending; touch, pressureAbIIIPain and cold receptors; some touch receptorsAdIVPain, temperature, and other receptorsDorsal root CNerve fiber susceptibility to conduction block produced by various agents.Susceptibility to:Most SusceptibleIntermediateLeast SusceptibleHypoxiaBACPressureABCLocal anestheticsCBA
AS fibres
Ap fibres
Aa fibres
C fibres
Nervous System