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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
2
|
| pubmed:dateCreated |
1987-11-9
|
| pubmed:abstractText |
The recruitment curves of the monosynaptic Hoffmann (H) reflex and of the direct motor (M) excitation of alpha-motor fibers of the posterior popliteal nerve were studied in seven human subjects in normoxic and hypoxic conditions at sea level. The amplitude of the H and M responses were determined from the computerized full-wave rectified and integrated surface electromyographic (EMG) signal derived from bipolar surface electrodes placed over the soleus muscle. Hypoxic exposure [end-tidal O2 fraction (FETO2) = 0.066 +/- 0.003 and end-tidal CO2 fraction (FETCO2) = 0.0504 +/- 0.001 (SE)] did not affect the maximal M (Mmax) response but decreased significantly (7%) the maximal H (Hmax) response. The Hmax/Mmax ratio decreased from 0.60 to 0.53. Furthermore, by fitting the rising phase of the recruitment curves of the H and M responses vs. stimulus intensity with linear regressions, hypoxia was found to produce a significant decrease of similar magnitude (6%) in the threshold of both the H and M responses with no change in slope. Using a constant stimulus strength eliciting an H response of half the maximum (H50%) of the control conditions, hypoxia resulted in a 50% increase in the amplitude of the H response within 12 min. These results suggest that the effects of hypoxia on the nervous system consist of a direct depolarizing action on the peripheral alpha-fibers and 1A sensory fibers and of a central effect on supraspinal structures affecting the spinal alpha-motoneurons.
|
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:status |
MEDLINE
|
| pubmed:month |
Aug
|
| pubmed:issn |
8750-7587
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
63
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
639-45
|
| pubmed:dateRevised |
2006-11-15
|
| pubmed:meshHeading |
pubmed-meshheading:3654424-Adult,
pubmed-meshheading:3654424-Anoxia,
pubmed-meshheading:3654424-Electric Stimulation,
pubmed-meshheading:3654424-Electromyography,
pubmed-meshheading:3654424-H-Reflex,
pubmed-meshheading:3654424-Humans,
pubmed-meshheading:3654424-Male,
pubmed-meshheading:3654424-Middle Aged,
pubmed-meshheading:3654424-Movement,
pubmed-meshheading:3654424-Recruitment, Neurophysiological,
pubmed-meshheading:3654424-Reflex, Monosynaptic,
pubmed-meshheading:3654424-Tibial Nerve
|
| pubmed:year |
1987
|
| pubmed:articleTitle |
Hypoxia and monosynaptic reflexes in humans.
|
| pubmed:affiliation |
Laboratory of Clinical Neurophysiology, Faculté de Médecine Saint-Antoine, Paris, France.
|
| pubmed:publicationType |
Journal Article
|