Exam 1 Flashcards
What is the motor nerve conduction?
alpha motoneurons in anterior horn > ventral root > motor axon > skeletal muscle
What is the sensory nerve conduction?
free nerve endings or specialized receptors > sensory axon > nerve cell bodies in DRG > dorsal root > dorsal horn
What is autonomic nerve conduction?
nerve cells in chain ganglia > autonomic axons > sweat glands > vascular smooth muscle
What is orthodromic conduction?
normal direction of conduction
i.e. sensory: peripheral moving centrally
What is antidromic conduction?
opposite direction of normal conduction
i.e. sensory: central moving peripherally
What are the conduction velocities?
a-alpha > a-beta > a-delta > c fibers
larger diameter, faster conduction
What is the peripheral nerve composition?
schwann cells, connective tissue, and vascular supply
What are the schwann cells?
cells arranged serially around the outside of the axons (nodes of Ranvier are the gaps between)
What connective tissue in the peripheral nerve?
epineurium (surrounding entire nerve for protection), perineurium (surrounding bundles/fascicles), and endoneurium (surrounds single nerve fiber)
How are the peripheral nerves vascularized?
each nerve fiber is vascularized
What are the classifications of nerve injuries?
class I- neurapraxia, class II- axonotmesis, class III- neurotmesis
What is neurapraxia?
blockage of nerve conduction without axonal interruption or degeneration (mild injury)
What are the characteristics of neurapraxia?
localized conduction block; no sign of axonal degeneration, excitability is essentially normal in the segments above and distal to the lesion; complete recovery occurs within days or weeks or even immediately after decompression
(muscle will respond to stimulation)
What are the clinical examples of neurapraxia?
temporary vascular occlusion; lidocaine or xylocaine injection, intentional; focal entrapment or compression
