Related Experiment Videos
[Electrophysiological aspects of peripheral nervous system development]
1Laboratoire de neurophysiologie, URA 1331 CNRS, faculté de médecine, Amiens, France.
Insights
Peripheral nerve maturation in infants shows that absolute refractory periods are established at birth and vary by fiber type, not conduction velocity. Muscle fiber refractory periods differ between premature and full-term neonates.
Area of Science:
- Neuroscience
- Developmental Biology
- Physiology
Context:
- Peripheral nervous system (PNS) maturation is crucial for infant development.
- Understanding nerve and muscle fiber excitability provides insights into neurological development.
Purpose:
- To investigate the maturation of peripheral nerve and muscle fibers in infants.
- To characterize absolute refractory periods and conduction velocities in different nerve fiber types.
Summary:
- Absolute refractory periods (ARPs) in nerve fibers are established at birth and are characteristic of fiber groups, independent of conduction velocity.
- Most excitable fibers exhibit smaller ARPs than motor fibers. Muscle fiber ARPs are higher in premature neonates compared to full-term neonates and adults.
- Conduction velocities indicate that type IA fibers have the highest velocities, with significant differences between fiber length development and postnatal diameter growth influencing conduction times.
Impact:
- Provides foundational data on normal PNS development in infants.
- Highlights distinct maturation patterns between nerve and muscle fibers.
- Offers insights into potential electrophysiological markers for assessing infant neurological status.
Abstract:
Different aspects of the maturation of the peripheral nervous system have been studied in infants, essentially during the first year of postnatal life. Absolute refractory periods which enable indirect estimation of excitability have been measured in both nerve and muscle fibers. It appears that already at birth, the absolute refractory period is characteristic for a given group of nerve fibres. In each group of nerve fibres, the absolute refractory period is not correlated to conduction velocity (ie fibre diameter) and remains rather constant during development. However, the absolute refractory period of the most excitable fibres is smaller than the absolute refractory period of motor fibres independent of the subject's age. On the other hand, the absolute refractory period of muscle fibres is slightly higher in premature in comparison with full-term neonates and adults. The diameter growth of different categories of nerve, fibers (motor--IA--non nociceptive cutaneous) is assessed by measurement of conduction velocities. At each age the IA fibre conduction velocities are the highest. The marked difference which exists between length development and postnatal increase of the fibre diameter explains the particular evolution of conduction times.