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At least 19 recordsLinked to original sources
PubMed1993

[Anesthesia and laryngeal muscle, especially intrinsic laryngeal muscles].

The intrinsic laryngeal muscles are highly specialized for phonation, respiration and sphincter activity. The muscles are disposed between three unpaired cartilages (the thyroid, cricothyroid and epiglottic) and the paired arytenoid cartilages. These laryngeal muscles, which are striated in character, are bilaterally disposed and can be grouped as adductors and abductors of the glottis and tensors of the vocal cords. The motor neurons for the intrinsic laryngeal muscles are located in the caudal half of the nucleus ambiguous. The intrinsic laryngeal muscles receive motor nerve supply from the external branches of the superior laryngeal and recurrent nerves on each side. The external branch of the superior laryngeal nerve serves in motor innervation of the cricothyroid muscle, while the other laryngeal muscles receive a motor innervation from the recurrent nerve. Compared with limb skeletal muscles, the intrinsic laryngeal muscle have unique morphologic and histochemical characteristics. In general, the intrinsic laryngeal muscle fibers contain greater percentages of histochemically type 1 fibers than limb skeletal muscles. In addition, morphometrical studies of the subneural apparatus at the neuromuscular junctions of the intrinsic laryngeal muscles demonstrate the difference between the morphological features of the nerve endings and the distribution pattern of the motor end-plates of the laryngeal muscles and those of the limb skeletal muscles. Finally, the influence of anesthetic drugs including neuromuscular blocking agents on the intrinsic laryngeal muscles is discussed. The gross anatomical features such as the motor innervation, localization of the neurons for the motor nerve fibers, and arrangement and characteristics of the motor end-plates of the intrinsic laryngeal muscles are described based on a review of literature and our current investigations.

Anesthesia↗
PubMed1982

Morphologic and histochemical characteristics of laryngeal muscle.

Laryngeal muscle (LM) is highly specialized for phonation and sphincter activity. We queried whether this specialization is reflected in the structure of LM. We examined, using histochemical techniques, the structure of five LM from three men who died suddenly and who had no evidence of laryngeal disease. Compared with nonlaryngeal skeletal muscle, our specimens demonstrated moderate fibrosis, rounding of fibers, basophilia, and ragged red fibers that were shown to be mitochondria. In general, LM fibers are smaller, have more variability in size, and contain a greater percentage of histochemically type 1 fibers than limb skeletal muscles. These differences suggest that theories of motor control derived from studies of limb skeletal muscles may not apply to LM.

Adenosine Triphosphatases↗
PubMedDate not supplied

Comparative histochemistry of human and sheep laryngeal muscles.

Four laryngeal muscles of human male, human female and sheep female cadavers were evaluated by histological, histochemical and quantitative techniques. The muscle fibre sizes showed significant differences between human male, female and sheep. Fibre diameters of male human laryngeal muscles were 2 to 4 microns larger than in female human and 11 to 13 microns larger than in sheep muscles. In the group of human laryngeal muscles, the posterior cricoarytenoid muscle contained the highest percentage (65%) of type I fibres. In sheep, the homologous muscle consists only of 45% type I fibres. On the other hand, in sheep the cricothyroid muscle showed significantly more type I fibres (58%) than the human counterpart (43%). In both species the vocal muscles had a rather low content of type I fibres (26 to 37%).

Animals↗
PubMed2000

Comparison of succinylcholine with two doses of rocuronium using a new method of monitoring neuromuscular block at the laryngeal muscles by surface laryngeal electromyography.

We compared the onset of neuromuscular block with succinylcholine (1 mg kg-1) and two doses of rocuronium (0.6 and 0.9 mg kg-1) at the adductor pollicis muscle using electromyography (EMG) and acceleromyography (AMG), and at the adductor laryngeal muscles with a new electromyographic method using a disposable surface electrode attached to the cuff of a tracheal tube. At the larynx, the mean (+/- SD) time to 90% block and the onset time of succinylcholine (38 +/- 15 and 47 +/- 19 s, respectively) were significantly shorter (P < 0.01) than for rocuronium 0.6 mg kg-1 (92 +/- 42 and 106 +/- 38 s) and rocuronium 0.9 mg kg-1 (52 +/- 31 and 64 +/- 30 s). We found that, with comparable degrees of neuromuscular block, the onset time of succinylcholine at the adductor pollicis was significantly shorter (P < 0.01) than for rocuronium 0.6 mg kg-1 and 0.9 mg kg-1 (EMG, 80 +/- 39 vs 145 +/- 48 s and 99 +/- 31 s; AMG, 90 +/- 39 vs 124 +/- 53 s and 106 +/- 38 s). Clinical duration at the adductor pollicis (AMG) was significantly longer (P < 0.01) for both rocuronium groups than for succinylcholine (T4:T1 = 0.7, 54 +/- 18 and 77 +/- 21 vs 8 +/- 6 min). The surface laryngeal electrode proved non-invasive, easy to use and reliable in measuring onset of the neuromuscular block at the larynx.

Adult↗
PubMed1976

Coordinated activities of middle-ear and laryngeal muscles in echolocating bats.

The middle-ear muscles and laryngeal muscles of the little brown bat (Myotis lucifugus) are highly developed. When the bat emits orientation sounds, action potentials of middle-ear muscles appear approximately 3 milliseconds after those of the laryngeal muscles; this activity of middle-ear muscles attenuates the vocal self-stimulation and improves the performance of the echolocation system. When an acoustic stimulus is delivered, both types of muscles contract; action potentials of the laryngeal muscles appear approximately 3 milliseconds after those of the middle-ear muscles. These two groups of muscles are apparently activated in a coordinated manner not only by the nerve impulses from the vocalization center, but also by those from the auditory system.

Action Potentials↗
PubMed2005

Proteomic analysis of rat laryngeal muscle following denervation.

Laryngeal muscle atrophy induced by nerve injury is a major factor contributing to the disabling symptoms associated with laryngeal paralysis. Alterations of global proteins in rat laryngeal muscle following denervation were, therefore, studied using proteomic techniques. Twenty-eight adult Sprague-Dawley rats were divided into normal control and denervated groups. The thyroarytenoid (TA) muscle was excised 60 days after right recurrent laryngeal nerve was resected. Protein separation and identification were preformed using 2-DE and MALDI-MS with database search. Forty-four proteins were found to have significant alteration in expression level after denervation. The majority of these proteins (57%), most of them associated with energy metabolism, cellular proliferation and differentiation, signal transduction and stress reaction, were decreased levels of expression in denervated TA muscle. The remaining 43% of the proteins, most of them involved with protein degradation, immunoreactivity, injury repair, contraction, and microtubular formation, were found to have increased levels of expression. The protein modification sites by phosphorylation were detected in 22% of the identified proteins that presented multiple-spot patterns on 2-D gel. Significant changes in protein expression in denervated laryngeal muscle may provide potential therapeutic strategies for the treatment of laryngeal paralysis.

Animals↗
PubMed2002

Multiple motor unit recordings of laryngeal muscles: the technique of vector laryngeal electromyography.

OBJECTIVES: To display time-series firing rate and recruitment data for multiple, simultaneously active motoneurons activating human laryngeal muscles. These data provide specific information about how laryngeal muscle force is being controlled by the central nervous system at the level of the lower motoneuron. METHODS: A quadrifilar needle electrode was used to record multi-channel myoelectric signals from thyroarytenoid muscle of normal subjects during tasks ranging from quiet breathing to a short sentence. Motor unit action potentials of the signal space were identified and tracked throughout task productions using pattern recognition and Precision Decomposition software. RESULTS: We present the first recordings and analyses of multiple motor unit activations in the larynx. The firing times and mean firing rates are plotted for each identified motor unit, which reveal recruitment and decruitment information and the database from which common firing statistics across motor units may be derived. CONCLUSIONS: This study provides new information about neuromuscular physiology of the larynx. Specifically, the results reveal the ordered recruitment and firing patterns of multiple motor units and the existence of common drive from the central nervous system. The technique may prove fundamental to understanding various neuromuscular pathologies such as laryngeal spasm and to assist clinical prognosis of laryngeal paresis and the diagnosis of certain neurogenic disorders.

Adult↗
PubMed2005

Central nervous system control of the laryngeal muscles in humans.

Laryngeal muscle control may vary for different functions such as: voice for speech communication, emotional expression during laughter and cry, breathing, swallowing, and cough. This review discusses the control of the human laryngeal muscles for some of these different functions. Sensori-motor aspects of laryngeal control have been studied by eliciting various laryngeal reflexes. The role of audition in learning and monitoring ongoing voice production for speech is well known; while the role of somatosensory feedback is less well understood. Reflexive control systems involving central pattern generators may contribute to swallowing, breathing and cough with greater cortical control during volitional tasks such as voice production for speech. Volitional control is much less well understood for each of these functions and likely involves the integration of cortical and subcortical circuits. The new frontier is the study of the central control of the laryngeal musculature for voice, swallowing and breathing and how volitional and reflexive control systems may interact in humans.

Brain↗
PubMedDate not supplied

Transposition of infrahyoid muscles to replace intrinsic laryngeal muscles: technique and long-time observations on return of function.

Insertion of the separate motor branches of the caudal laryngeal nerve of the dog separately and atraumatically into a denervated infrahyoid muscle resulted in reinnervation of that muscle, as indicated by the appearance of electromyographic potentials two months postoperatively. When the nerve branches were used to reinnervate a sufficiently large mass of muscle, which was transposed to replace surgically removed intrinsic laryngeal muscles, nearly normal adduction and abduction of the vocal cord was obtained on the experimental side in some dog if ample time were allowed for maturation of nerve fibers and motor end plates. The minimum time for return of effective function under these circumstances was slightly more than 12 months, and function may improve for up to 36 months. A simplified procedure is described for reconstructing the intrinsic laryngeal muscles following submucosal resection. Electromyography is useful in monitoring the progress of reinnervation of muscle, but it is not a reliable indicator of mechanical function.

Action Potentials↗
PubMed1978

Laryngeal muscle activity during stuttering.

Laryngeal muscle activity during fluent and stuttered utterances was investigated via electromyography. Analysis revealed that stuttering was accompanied by high levels of laryngeal muscle activity and disruption of normal reciprocity between abductor and adductor muscle groups. Results are interpreted as demonstrating the existence of a laryngeal component in stuttering and showing a strong correlation between abnormal laryngeal muscle activity and moments of stuttering.

Action Potentials↗
PubMed2005

Laryngeal muscle fibre types.

The internal laryngeal muscles have evolved to subserve the highly specialized functions of airways protection, respiration, and phonation. Their contractile properties, histochemistry, biochemical properties, myosin heavy chain (MyHC) expression and their regulation by nerves and hormones are reviewed and compared with limb muscle fibres. Cricothyroid, the vocal cord tensor, is limb-like in MyHC composition and fibre type properties, while the vocal fold abductor and adductors are allotypically different, with capacity for expressing an isoform of MyHC that is kinetically faster than the fastest limb MyHC. In rats and rabbits the faster isoform is the extraocular (EO) MyHC, while in carnivores, it is the IIB MyHC. These adaptations enable the abductor and adductor muscles to remain always faster than the cricothyroid as the latter changes in speed during evolution to match changing metabolic and respiratory rates in relation to scaling with body mass. Such phylogenetic plasticity is vital to the airways protection and respiratory functions of these muscles. The posterior cricoarythenoid, the abductor muscle, is tonically driven during expiration, and consequently has a slower fibre type profile than the principal adductor, the thyroarythenoid. The human thyroarythenoid appears not to express EO or IIB MyHC significantly, but is unique in expressing the slow-tonic MyHC. The concepts of allotype and phylogenetic plasticity help to explain differences in fibre type between limb and laryngeal muscles and between homologous laryngeal muscles in different species. Laryngeal muscle fibres exhibit physiological plasticity as do limb muscles, being subject to neural and hormonal modulation.

Adaptation, Physiological↗
PubMed1995

Expression of extraocular myosin heavy chain in rabbit laryngeal muscle.

The intrinsic laryngeal muscles of mammals are functionally heterogeneous, some of these muscles (e.g. the thyroarytenoid) contract extremely rapidly, like extraocular muscle, whilst others (e.g. the cricothyroid) contract as fast as limb fast muscle. The extraordinarily rapid contraction speed of extraocular muscles is associated with a fast myosin not found in limb muscles. In this work we explored the possibility that the thyroarytenoid muscle may also express this extraocular-specific fast myosin by raising a monoclonal antibody (mab 4A6) against its heavy chain. Electrophoretic separation of native isomyosins revealed that both the extraocular and the thyroarytenoid have two similar bands migrating ahead of bands found in limb fast or cricothyroid myosins. These two bands bound mab 4A6. The thyroarytenoid muscle can be divided into two divisions, a vocalis division which is important in phonation and an external division which functions in closing the glottis. Fibres in the vocalis are heterogeneous, some stain with mab 4A6, whilst others stain with mabs against limb myosin heavy chains. Fibres in the external division stain almost homogeneous with mab 4A6. The immunohistochemical staining pattern in the cricothyroid muscle resembled that of fast limb muscle: no fibres stained with mab 4A6. Thus, the high speed of contraction of the thyroarytenoid is associated with the same myosin heavy chain found in extraocular muscles, this characteristic is presumably an evolutionary adaptation for rapid closure of the glottis to enhance airway defense mechanisms.

Animals↗
PubMed1997

Innervation of adult human laryngeal muscle fibers.

The innervation of laryngeal muscle fibers was appraised in adult humans. Sixteen intrinsic laryngeal muscles were dissected during the autopsy of 4 adults (41-71 years old). Longitudinal serial frozen sections, 60 microm thick, of the whole muscles were double-stained for cholinesterase activity and axonal visualization. About 945 endplates per muscle were analysed using light microscopy. The neuromuscular junctions were always scattered throughout the whole muscles. Most of the muscle fibers showed a single neuromuscular junction, but multi-innervated fibers were found in all of the muscles. Their number was highest in interarytenoid muscles (21% of all the fibers). The distance between multiple neuromuscular junctions was most frequently less than 150 microm. Two neuromuscular junctions were frequently displayed, opposite one another, particularly in thyroarytenoid muscles, and this unusual feature seems specific for laryngeal muscles. The innervation of all of the muscle fibers was exclusively found to be unineuronal, with multi-innervated fibers being innervated by a single axon. Distal axonal degeneration occurred with aging, resulting in a loss in the number of multi-innervated muscle fibers.

Adult↗