Recruitment and suprathreshold frequency modulation of single extraocular muscle fibers in the rabbit

N. H. Barmack

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The isometric tension developed by the inferior rectus muscle of the rabbit was modulated by the vestibuloocular reflex (VOR) in unanesthetized rabbits. Single muscle fiber activity was recorded from the inferior rectus muscle during reflex activation. The force at which a muscle fiber was recruited and its suprathreshold frequency-force relationship were studied. The size of individual motor units was measured by averaging the tension which was 'time-locked' to the discharge of a single muscle fiber. The average motor unit twitch amplitude was 1.3 mg. The suprathreshold frequency-force function was characterized by an initially steep slope, followed by a less steep slope, until a level of saturation was reached at higher forces. Motor unit size was linearly related to recruitment threshold. Small motor units also had a significantly steeper frequency-force relationship than larger motor units. The relationship between motor unit size and recruitment threshold appears to compensate for changes in the operating point on the length-tension curve of extraocular muscle.

Original languageEnglish (US)
Pages (from-to)779-790
Number of pages12
JournalJournal of Neurophysiology
Volume40
Issue number4
StatePublished - 1977

Fingerprint

Oculomotor Muscles
Rabbits
Muscles
Neurophysiological Recruitment
Vestibulo-Ocular Reflex
Reflex

ASJC Scopus subject areas

  • Physiology
  • Neuroscience(all)

Cite this

Recruitment and suprathreshold frequency modulation of single extraocular muscle fibers in the rabbit. / Barmack, N. H.

In: Journal of Neurophysiology, Vol. 40, No. 4, 1977, p. 779-790.

Research output: Contribution to journalArticle

@article{0353488bba05404ab479bd86efe4c268,
title = "Recruitment and suprathreshold frequency modulation of single extraocular muscle fibers in the rabbit",
abstract = "The isometric tension developed by the inferior rectus muscle of the rabbit was modulated by the vestibuloocular reflex (VOR) in unanesthetized rabbits. Single muscle fiber activity was recorded from the inferior rectus muscle during reflex activation. The force at which a muscle fiber was recruited and its suprathreshold frequency-force relationship were studied. The size of individual motor units was measured by averaging the tension which was 'time-locked' to the discharge of a single muscle fiber. The average motor unit twitch amplitude was 1.3 mg. The suprathreshold frequency-force function was characterized by an initially steep slope, followed by a less steep slope, until a level of saturation was reached at higher forces. Motor unit size was linearly related to recruitment threshold. Small motor units also had a significantly steeper frequency-force relationship than larger motor units. The relationship between motor unit size and recruitment threshold appears to compensate for changes in the operating point on the length-tension curve of extraocular muscle.",
author = "Barmack, {N. H.}",
year = "1977",
language = "English (US)",
volume = "40",
pages = "779--790",
journal = "Journal of Neurophysiology",
issn = "0022-3077",
publisher = "American Physiological Society",
number = "4",

}

TY - JOUR

T1 - Recruitment and suprathreshold frequency modulation of single extraocular muscle fibers in the rabbit

AU - Barmack, N. H.

PY - 1977

Y1 - 1977

N2 - The isometric tension developed by the inferior rectus muscle of the rabbit was modulated by the vestibuloocular reflex (VOR) in unanesthetized rabbits. Single muscle fiber activity was recorded from the inferior rectus muscle during reflex activation. The force at which a muscle fiber was recruited and its suprathreshold frequency-force relationship were studied. The size of individual motor units was measured by averaging the tension which was 'time-locked' to the discharge of a single muscle fiber. The average motor unit twitch amplitude was 1.3 mg. The suprathreshold frequency-force function was characterized by an initially steep slope, followed by a less steep slope, until a level of saturation was reached at higher forces. Motor unit size was linearly related to recruitment threshold. Small motor units also had a significantly steeper frequency-force relationship than larger motor units. The relationship between motor unit size and recruitment threshold appears to compensate for changes in the operating point on the length-tension curve of extraocular muscle.

AB - The isometric tension developed by the inferior rectus muscle of the rabbit was modulated by the vestibuloocular reflex (VOR) in unanesthetized rabbits. Single muscle fiber activity was recorded from the inferior rectus muscle during reflex activation. The force at which a muscle fiber was recruited and its suprathreshold frequency-force relationship were studied. The size of individual motor units was measured by averaging the tension which was 'time-locked' to the discharge of a single muscle fiber. The average motor unit twitch amplitude was 1.3 mg. The suprathreshold frequency-force function was characterized by an initially steep slope, followed by a less steep slope, until a level of saturation was reached at higher forces. Motor unit size was linearly related to recruitment threshold. Small motor units also had a significantly steeper frequency-force relationship than larger motor units. The relationship between motor unit size and recruitment threshold appears to compensate for changes in the operating point on the length-tension curve of extraocular muscle.

UR - http://www.scopus.com/inward/record.url?scp=0017645837&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0017645837&partnerID=8YFLogxK

M3 - Article

C2 - 301927

AN - SCOPUS:0017645837

VL - 40

SP - 779

EP - 790

JO - Journal of Neurophysiology

JF - Journal of Neurophysiology

SN - 0022-3077

IS - 4

ER -