scholarly journals Inability to increase the neural drive to muscle is associated with task failure during submaximal contractions

2020 ◽  
Vol 124 (4) ◽  
pp. 1110-1121 ◽  
Author(s):  
Eduardo Martinez-Valdes ◽  
Francesco Negro ◽  
Deborah Falla ◽  
Jakob Lund Dideriksen ◽  
C. J. Heckman ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Firing Rate ◽  
Motor Unit ◽  
Time To Failure ◽  
Neural Drive ◽  
Tracking Technique ◽  
Motor Unit Firing ◽  
Submaximal Contraction ◽  
The Central Nervous System

Motor unit firing and contractile properties during a submaximal contraction until failure were assessed with a new tracking technique. Two distinct phases in firing behavior were observed, which compensated for changes in twitch area and predicted time to failure. However, the late increase in firing rate was below the rates attained in the absence of fatigue, which points to an inability of the central nervous system to sufficiently increase the neural drive to muscle with fatigue.

scholarly journals Central nervous system modulates the neuromechanical delay in a broad range for the control of muscle force

2018 ◽  
Vol 125 (5) ◽  
pp. 1404-1410 ◽  
Author(s):  
A. Del Vecchio ◽  
A. Úbeda ◽  
M. Sartori ◽  
J. M. Azorín ◽  
F. Felici ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Motor Unit ◽  
Neural Coding ◽  
Neural Control ◽  
Motor Units ◽  
Force Generation ◽  
Neural Drive ◽  
Wide Range ◽  
The Central Nervous System

Force is generated by muscle units according to the neural activation sent by motor neurons. The motor unit is therefore the interface between the neural coding of movement and the musculotendinous system. Here we propose a method to accurately measure the latency between an estimate of the neural drive to muscle and force. Furthermore, we systematically investigate this latency, which we refer to as the neuromechanical delay (NMD), as a function of the rate of force generation. In two experimental sessions, eight men performed isometric finger abduction and ankle dorsiflexion sinusoidal contractions at three frequencies and peak-to-peak amplitudes {0.5, 1, and 1.5 Hz; 1, 5, and 10 of maximal force [%maximal voluntary contraction (MVC)]}, with a mean force of 10% MVC. The discharge timings of motor units of the first dorsal interosseous (FDI) and tibialis anterior (TA) muscle were identified by high-density surface EMG decomposition. The neural drive was estimated as the cumulative discharge timings of the identified motor units. The neural drive predicted 80 ± 0.4% of the force fluctuations and consistently anticipated force by 194.6 ± 55 ms (average across conditions and muscles). The NMD decreased nonlinearly with the rate of force generation ( R2 = 0.82 ± 0.07; exponential fitting) with a broad range of values (from 70 to 385 ms) and was 66 ± 0.01 ms shorter for the FDI than TA ( P < 0.001). In conclusion, we provided a method to estimate the delay between the neural control and force generation, and we showed that this delay is muscle-dependent and is modulated within a wide range by the central nervous system. NEW & NOTEWORTHY The motor unit is a neuromechanical interface that converts neural signals into mechanical force with a delay determined by neural and peripheral properties. Classically, this delay has been assessed from the muscle resting level or during electrically elicited contractions. In the present study, we introduce the neuromechanical delay as the latency between the neural drive to muscle and force during variable-force contractions, and we show that it is broadly modulated by the central nervous system.

scholarly journals Reduced motoneuron excitability in a rat model of sepsis

2013 ◽  
Vol 109 (7) ◽  
pp. 1775-1781 ◽  
Author(s):  
Paul Nardelli ◽  
Jaffar Khan ◽  
Randall Powers ◽  
Tim C. Cope ◽  
Mark M. Rich
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Intensive Care ◽  
Motor Unit ◽  
Action Potentials ◽  
Cecal Ligation ◽  
Membrane Properties ◽  
Whole Body ◽  
Repetitive Firing ◽  
The Central Nervous System

Many critically ill patients in intensive care units suffer from an infection-induced whole body inflammatory state known as sepsis, which causes severe weakness in patients who survive. The mechanisms by which sepsis triggers intensive care unit-acquired weakness (ICUAW) remain unclear. Currently, research into ICUAW is focused on dysfunction of the peripheral nervous system. During electromyographic studies of patients with ICUAW, we noticed that recruitment was limited to few motor units, which fired at low rates. The reduction in motor unit rate modulation suggested that functional impairment within the central nervous system contributes to ICUAW. To understand better the mechanism underlying reduced firing motor unit firing rates, we moved to the rat cecal ligation and puncture model of sepsis. In isoflurane-anesthetized rats, we studied the response of spinal motoneurons to injected current to determine their capacity for initiating and firing action potentials repetitively. Properties of single action potentials and passive membrane properties of motoneurons from septic rats were normal, suggesting excitability was normal. However, motoneurons exhibited striking dysfunction during repetitive firing. The sustained firing that underlies normal motor unit activity and smooth force generation was slower, more erratic, and often intermittent in septic rats. Our data are the first to suggest that reduced excitability of neurons within the central nervous system may contribute to ICUAW.

Principles of Motor Unit Physiology Evolve With Advances in Technology

Physiology ◽  
2016 ◽  
Vol 31 (2) ◽  
pp. 83-94 ◽  
Author(s):  
Dario Farina ◽  
Francesco Negro ◽  
Silvia Muceli ◽  
Roger M. Enoka
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Motor Unit ◽  
Unit Activity ◽  
Motor Units ◽  
Motor Unit Activity ◽  
Technological Advances ◽  
The Central Nervous System

Movements are generated by the coordinated activation of motor units. Recent technological advances have made it possible to identify the concurrent activity of several tens of motor units, in contrast with much smaller samples available in classic studies. We discuss how these advances in technology have enabled the development of a population perspective of how the central nervous system controls motor unit activity and thereby the forces exerted by muscles.

Effects of Hyperoxia on Lung Utrastructure

1970 ◽  
Vol 28 ◽  
pp. 26-27
Author(s):  
Gladys Harrison
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Light Microscopy ◽  
Oxygen Effects ◽  
Age Dependent ◽  
The Central Nervous System ◽  
The Subject ◽  
Space Age ◽  
Alveolar Septa ◽  
Extensive Damage

With the advent of the space age and the need to determine the requirements for a space cabin atmosphere, oxygen effects came into increased importance, even though these effects have been the subject of continuous research for many years. In fact, Priestly initiated oxygen research when in 1775 he published his results of isolating oxygen and described the effects of breathing it on himself and two mice, the only creatures to have had the “privilege” of breathing this “pure air”.Early studies had demonstrated the central nervous system effects at pressures above one atmosphere. Light microscopy revealed extensive damage to the lungs at one atmosphere. These changes which included perivascular and peribronchial edema, focal hemorrhage, rupture of the alveolar septa, and widespread edema, resulted in death of the animal in less than one week. The severity of the symptoms differed between species and was age dependent, with young animals being more resistant.

Emigration of neutrophils in the central nervous system

1983 ◽  
Vol 41 ◽  
pp. 788-789
Author(s):  
John L.Beggs ◽  
John D. Waggener ◽  
Wanda Miller ◽  
Jane Watkins
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Osmium Tetroxide ◽  
White Blood Cells ◽  
Arterial Perfusion ◽  
E Coli ◽  
Intracisternal Injection ◽  
The Central Nervous System ◽  
Brain And Spinal Cord ◽  
Interendothelial Junctions

Studies using mesenteric and ear chamber preparations have shown that interendothelial junctions provide the route for neutrophil emigration during inflammation. The term emigration refers to the passage of white blood cells across the endothelium from the vascular lumen. Although the precise pathway of transendo- thelial emigration in the central nervous system (CNS) has not been resolved, the presence of different physiological and morphological (tight junctions) properties of CNS endothelium may dictate alternate emigration pathways.To study neutrophil emigration in the CNS, we induced meningitis in guinea pigs by intracisternal injection of E. coli bacteria.In this model, leptomeningeal inflammation is well developed by 3 hr. After 3 1/2 hr, animals were sacrificed by arterial perfusion with 3% phosphate buffered glutaraldehyde. Tissues from brain and spinal cord were post-fixed in 1% osmium tetroxide, dehydrated in alcohols and propylene oxide, and embedded in Epon. Thin serial sections were cut with diamond knives and examined in a Philips 300 electron microscope.

Mammalian Bone Marrow Acetylcholinesterase

1982 ◽  
Vol 40 ◽  
pp. 44-45
Author(s):  
Ezzatollah Keyhani
Keyword(s):  
Central Nervous System ◽  
Bone Marrow ◽  
Nervous System ◽  
Common Property ◽  
Extracellular Medium ◽  
The Central Nervous System ◽  
The Common ◽  
Mammalian Bone

Acetylcholinesterase (EC 3.1.1.7) (ACHE) has been localized at cholinergic junctions both in the central nervous system and at the periphery and it functions in neurotransmission. ACHE was also found in other tissues without involvement in neurotransmission, but exhibiting the common property of transporting water and ions. This communication describes intracellular ACHE in mammalian bone marrow and its secretion into the extracellular medium.

Glucuronyl 3-sulfate occurs exclusively on distal unmyelinated terminals of selected sensory neurons in the peripheral nervous system

1995 ◽  
Vol 53 ◽  
pp. 958-959
Author(s):  
S.S. Spicer ◽  
B.A. Schulte
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Cerebral Cortex ◽  
Peripheral Nervous System ◽  
Sensory Neurons ◽  
Sensory Nerves ◽  
Tissue Antigens ◽  
The Central Nervous System ◽  
The Brain ◽  
Leu 7

Generation of monoclonal antibodies (MAbs) against tissue antigens has yielded several (VC1.1, HNK- 1, L2, 4F4 and anti-leu 7) which recognize the unique sugar epitope, glucuronyl 3-sulfate (Glc A3- SO4). In the central nervous system, these MAbs have demonstrated Glc A3-SO4 at the surface of neurons in the cerebral cortex, the cerebellum, the retina and other widespread regions of the brain.Here we describe the distribution of Glc A3-SO4 in the peripheral nervous system as determined by immunostaining with a MAb (VC 1.1) developed against antigen in the cat visual cortex. Outside the central nervous system, immunoreactivity was observed only in peripheral terminals of selected sensory nerves conducting transduction signals for touch, hearing, balance and taste. On the glassy membrane of the sinus hair in murine nasal skin, just deep to the ringwurt, VC 1.1 delineated an intensely stained, plaque-like area (Fig. 1). This previously unrecognized structure of the nasal vibrissae presumably serves as a tactile end organ and to our knowledge is not demonstrable by means other than its selective immunopositivity with VC1.1 and its appearance as a densely fibrillar area in H&E stained sections.

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