Nerve conduction Sompol Tapechum M.D., Ph.D. Department of Physiology
Faculty of Medicine Siriraj Hospital Objectives nerve conduction velocity nerve conduction velocity nerve conduction velocity axon Nervous system Structure of Nervous system
Central nervous system (CNS) Brain Cerebrum Cerebellum Brainstem Spinal cord Peripheral nervous system (PNS) Nerves Cranial nerve 12 pairs Spinal nerve 31 pairs Spinal nerve and Cranial nerve Nerve structure Nerve = Bundle of axon Component of nerve Motor
Somatic Autonomic Sensory Visceral Axon Motor neurons Sensory neurons Orthodromic Antidromic Orthodromic Types of axon Type of axon Information Processed
Table I Somatosensory Receptors and their Peripheral Axons Receptor Type Axon3 Group CAP Peak Conduction Velocity Axon Diameter Information Processed Muscle Spindle: Annulospiral endings Ia Aa m/sec mM Muscle length and velocity Muscle Spindle: Flower Spray endings II Ab m/sec mM Muscle length Golgi Tendon Organ Ib Muscle tension Joint: Pacinian Joint movement Joint: Ruffini Joint angle Joint: Golgi Tendon Organ Joint torque Meissner corpuscle Touch, flutter or movement Pacinian corpuscle Vibration Ruffini corpuscle Skin stretch Hair follicle II & III Ab & Ad m/sec 2 -12 mM Touch movement Merkel complex Fine touch Free Nerve Endings III Ad m/sec 1 - 6 mM Sharp pain or cool/cold IV C m/sec < 1.5 mM Dull or aching pain, or touch or warm Nerve conduction Sensory conduction study
Antidromic Sensory conduction study
Orthodromic Motor conduction study
Orthodromic Median nerve Motor conduction study: Median nerve Motor neuron Neuromuscular junction Neuromuscular junction Nerve conduction velocity
NCV = D1-D2 L1-L2 D1 Latency (s)L1 L2 Sensory conduction study: Median nerve Purposes of Nerve conduction study
To diagnose nerve damage or destruction To follow up nerve regeneration after damage To evaluate diseases of nerve or muscle Normal nerve conduction velocity
normal conduction velocity approximately 50 to 60 meters per second. may vary from one individual to another and from one nerve to another. Carpal tunnel syndrome Nerve injury Axon regeneration 2-4 mm/day Myasthenia gravis