scholarly journals An integrated mathematical model of the human cardiopulmonary system: model development

2016 ◽  
Vol 310 (7) ◽  
pp. H899-H921 ◽  
Author(s):  
Antonio Albanese ◽  
Limei Cheng ◽  
Mauro Ursino ◽  
Nicolas W. Chbat
Keyword(s):  
Neural Control ◽  
Model Development ◽  
Control Mechanisms ◽  
Short Term ◽  
Physiological Variables ◽  
Animal Data ◽  
Adult Humans ◽  
Underlying Mechanisms ◽  
Cardiopulmonary System ◽  
Alveolar Gas Exchange

Several cardiovascular and pulmonary models have been proposed in the last few decades. However, very few have addressed the interactions between these two systems. Our group has developed an integrated cardiopulmonary model (CP Model) that mathematically describes the interactions between the cardiovascular and respiratory systems, along with their main short-term control mechanisms. The model has been compared with human and animal data taken from published literature. Due to the volume of the work, the paper is divided in two parts. The present paper is on model development and normophysiology, whereas the second is on the model's validation on hypoxic and hypercapnic conditions. The CP Model incorporates cardiovascular circulation, respiratory mechanics, tissue and alveolar gas exchange, as well as short-term neural control mechanisms acting on both the cardiovascular and the respiratory functions. The model is able to simulate physiological variables typically observed in adult humans under normal and pathological conditions and to explain the underlying mechanisms and dynamics.

scholarly journals Early Lipid Raft-Related Changes: Interplay between Unilateral Denervation and Hindlimb Suspension

2021 ◽  
Vol 22 (5) ◽  
pp. 2239
Author(s):  
Irina G. Bryndina ◽  
Maria N. Shalagina ◽  
Vladimir A. Protopopov ◽  
Alexey V. Sekunov ◽  
Andrey L. Zefirov ◽  
...  
Keyword(s):  
Lipid Raft ◽  
Hindlimb Suspension ◽  
Short Term ◽  
Antiapoptotic Protein ◽  
Muscle Disuse ◽  
Proapoptotic Protein ◽  
Raft Fraction ◽  
Rat Soleus Muscle ◽  
Afferent Inputs ◽  
Underlying Mechanisms

Muscle disuse and denervation leads to muscle atrophy, but underlying mechanisms can be different. Previously, we have found ceramide (Cer) accumulation and lipid raft disruption after acute hindlimb suspension (HS), a model of muscle disuse. Herein, using biochemical and fluorescent approaches the influence of unilateral denervation itself and in combination with short-term HS on membrane-related parameters of rat soleus muscle was studied. Denervation increased immunoexpression of sphingomyelinase and Cer in plasmalemmal regions, but decreased Cer content in the raft fraction and enhanced lipid raft integrity. Preliminary denervation suppressed (1) HS-induced Cer accumulation in plasmalemmal regions, shown for both nonraft and raft-fractions; (2) HS-mediated decrease in lipid raft integrity. Similar to denervation, inhibition of the sciatic nerve afferents with capsaicin itself increased Cer plasmalemmal immunoexpression, but attenuated the membrane-related effects of HS. Finally, both denervation and capsaicin treatment increased immunoexpression of proapoptotic protein Bax and inhibited HS-driven increase in antiapoptotic protein Bcl-2. Thus, denervation can increase lipid raft formation and attenuate HS-induced alterations probably due to decrease of Cer levels in the raft fraction. The effects of denervation could be at least partially caused by the loss of afferentation. The study points to the importance of motor and afferent inputs in control of Cer distribution and thereby stability of lipid rafts in the junctional and extrajunctional membranes of the muscle.

Attention Biases Visual Activity in Visual Short-term Memory

2014 ◽  
Vol 26 (7) ◽  
pp. 1377-1389 ◽  
Author(s):  
Bo-Cheng Kuo ◽  
Mark G. Stokes ◽  
Alexandra M. Murray ◽  
Anna Christina Nobre
Keyword(s):  
Large Scale ◽  
Short Term Memory ◽  
Control Mechanisms ◽  
Top Down ◽  
Short Term ◽  
Visual Activity ◽  
Visual Short Term Memory ◽  
Large Scale Network ◽  
Visual Areas ◽  
Scale Network

In the current study, we tested whether representations in visual STM (VSTM) can be biased via top–down attentional modulation of visual activity in retinotopically specific locations. We manipulated attention using retrospective cues presented during the retention interval of a VSTM task. Retrospective cues triggered activity in a large-scale network implicated in attentional control and led to retinotopically specific modulation of activity in early visual areas V1–V4. Importantly, shifts of attention during VSTM maintenance were associated with changes in functional connectivity between pFC and retinotopic regions within V4. Our findings provide new insights into top–down control mechanisms that modulate VSTM representations for flexible and goal-directed maintenance of the most relevant memoranda.

Abnormal auditory N400 in a case of zolpidem dependence, during a working memory test

2006 ◽  
Vol 21 (2) ◽  
pp. 135-137 ◽  
Author(s):  
Ioannis A. Liappas ◽  
Charalabos C. Papageorgiou ◽  
Andreas D. Rabavilas
Keyword(s):  
Working Memory ◽  
Spatial Working Memory ◽  
Event Related Potentials ◽  
Short Term ◽  
Context Processing ◽  
Gaba A ◽  
Related Potentials ◽  
N400 Component ◽  
Underlying Mechanisms ◽  
Term Management

AbstractZolpidem is a GABA (A) agonist, which is indicated for the short-term management of insomnia. Recent research provide evidence suggesting that zolpidem produces spatial working memory (WM) deficits and dependence; however, the underlying mechanisms of these effects are unknown. Since the auditory N400 component of event-related potentials (ERPS) is considered as an index of memory use of context processing, the present study focused on N400 waveform of ERPs elicited during a WM task in a case suffering from zolpidem dependence. The patterns of N400 waveform of this case were compared to the patterns obtained from healthy controls. This comparison revealed that zolpidem dependence is accompanied by reduced amplitudes located at posterior brain areas and diffuse prolongation of N400. These findings may indicate that zolpidem dependence manifests alterations with regard to the memory use of context processing, involving or affecting a wide-ranging network of the brain's structures.

scholarly journals Aquifer-eustasy as the main driver of short-term sea-level fluctuations during Cretaceous hothouse climate phases

2019 ◽  
Vol 498 (1) ◽  
pp. 9-38 ◽  
Author(s):  
Benjamin Sames ◽  
M. Wagreich ◽  
C. P. Conrad ◽  
S. Iqbal
Keyword(s):  
Sea Level ◽  
Phase Relationship ◽  
Sea Level Changes ◽  
Short Term ◽  
Groundwater Levels ◽  
Sequence Stratigraphic ◽  
Sea Level Fluctuations ◽  
Minimum Estimate ◽  
Underlying Mechanisms ◽  
Continental Ice Sheets

AbstractA review of short-term (<3 myr: c. 100 kyr to 2.4 myr) Cretaceous sea-level fluctuations of several tens of metres indicates recent fundamental progress in understanding the underlying mechanisms for eustasy, both in timing and in correlation. Cretaceous third- and fourth-order hothouse sea-level changes, the sequence-stratigraphic framework, are linked to Milankovitch-type climate cycles, especially the longer-period sequence-building bands of 405 kyr and 1.2 myr. In the absence of continental ice sheets during Cretaceous hothouse phases (e.g. Cenomanian–Turonian), growing evidence indicates groundwater-related sea-level cycles: (1) the existence of Milankovitch-type humid-arid climate oscillations, proven via intense humid weathering records during times of regression and sea-level lowstands; (2) missing or inverse relationships of sea-level and the marine δ18O archives, i.e. the lack of a pronounced positive excursion, cooling signal during sea-level lowstands; and (3) the anti-phase relationship of sea and lake levels, attesting to high groundwater levels and charged continental aquifers during sea-level lowstands. This substantiates the aquifer-eustasy hypothesis. Rates of aquifer-eustatic sea-level change remain hard to decipher; however, reconstructions range from a very conservative minimum estimate of 0.04 mm a−1 (longer time intervals) to 0.7 mm a−1 (shorter, probably asymmetric cycles). Remarkably, aquifer-eustasy is recognized as a significant component for the Anthropocene sea-level budget.

Resituating cognitive mechanisms within heterarchical networks controlling physiology and behavior

2019 ◽  
Vol 29 (5) ◽  
pp. 620-639 ◽  
Author(s):  
William Bechtel
Keyword(s):  
Cognitive Control ◽  
Cognitive Science ◽  
Neural Control ◽  
Science Research ◽  
Control Mechanisms ◽  
Cognitive Mechanisms ◽  
Physiological Processes ◽  
High Level ◽  
And Behavior ◽  
Production Mechanisms

Cognitive science has traditionally focused on mechanisms involved in high-level reasoning and problem-solving processes. Such mechanisms are often treated as autonomous from but controlling underlying physiological processes. I offer a different perspective on cognition which starts with the basic production mechanisms through which organisms construct and repair themselves and navigate their environments and then I develop a framework for conceptualizing how cognitive control mechanisms form a heterarchical network that regulates production mechanisms. Many of these control mechanisms perform cognitive tasks such as evaluating circumstances and making decisions. Cognitive control mechanisms are present in individual cells, but in metazoans, intracellular control is supplemented by a nervous system in which a multitude of neural control mechanisms are organized heterarchically. On this perspective, high-level cognitive mechanisms are not autonomous, but are elements in larger heterarchical networks. This has implications for future directions in cognitive science research.

Autonomic Neural Control Mechanisms and the Release of Adrenal Steroids after Hypoglycaemia in Man

2008 ◽  
Vol 16 (S 1) ◽  
pp. 138-141 ◽  
Author(s):  
B. Frier ◽  
E. A. S. Al-Dujaili ◽  
R. J. M. Corrall ◽  
J. Pritchard ◽  
C. R. W. Edwards
Keyword(s):  
Neural Control ◽  
Control Mechanisms ◽  
Adrenal Steroids

Blood volume redistribution from a passive elastic permeable microcirculation due to hypovolemia

1994 ◽  
Vol 266 (6) ◽  
pp. H2268-H2278
Author(s):  
A. J. LaForte ◽  
L. P. Lee ◽  
G. F. Rich ◽  
T. C. Skalak ◽  
J. S. Lee
Keyword(s):  
Blood Volume ◽  
Plasma Density ◽  
Neural Control ◽  
Circulation Model ◽  
Volume Of Fluid ◽  
Time Interval ◽  
Short Term ◽  
Local Regulation ◽  
Pentobarbital Sodium ◽  
Volume Shift

We measured the variations in blood and plasma density for a cyclic hemorrhage protocol in conscious rabbits to calculate delta Vf [the volume of fluid restituted into the circulation from the time the blood volume was at its control to that after the hemorrhage of a blood volume (delta V)] and delta Vs (the volume shift from micro- to macrocirculation over the same time interval). We found that delta Vf is 7% of delta V and delta Vs 60% of delta V. They combine to reduce the effect of hemorrhage on macrovascular volume by 67% of delta V. Based on a two-resistor circulation model, the change in microcirculatory pressure (delta Pmic) from control to hemorrhage was estimated from the measured cardiac outputs and arterial and venous pressures. The computations indicate that delta Vs (or delta Vf) is linearly related to delta Pmic. With one relation fitting all data of rabbits that were conscious, infused with hexamethonium, and anesthetized with pentobarbital sodium, we concluded that the two short-term volume redistributions are not direct neural control or local regulation, but the response of a passive, permeable microcirculation to delta Pmic. From the linear relations, we obtained 0.88 ml.mmHg-1.kg-1 as the compliance of the rabbit microcirculation and 0.21 ml.min-1.mmHg-1.kg-1 as its filtration coefficient.

scholarly journals Interlimb Coordination in Human Crawling Reveals Similarities in Development and Neural Control With Quadrupeds

2009 ◽  
Vol 101 (2) ◽  
pp. 603-613 ◽  
Author(s):  
Susan K. Patrick ◽  
J. Adam Noah ◽  
Jaynie F. Yang
Keyword(s):  
Neural Control ◽  
Force Plate ◽  
Interlimb Coordination ◽  
Limb Length ◽  
Bipedal Walking ◽  
Human Infants ◽  
Hind Limbs ◽  
Underlying Mechanisms ◽  
Hands And Feet ◽  
Coordination Patterns

The study of quadrupeds has furnished most of our understanding of mammalian locomotion. To allow a more direct comparison of coordination between the four limbs in humans and quadrupeds, we studied crawling in the human, a behavior that is part of normal human development and mechanically more similar to quadrupedal locomotion than is bipedal walking. Interlimb coordination during hands-and-knees crawling is compared between humans and quadrupeds and between human infants and adults. Mechanical factors were manipulated during crawling to understand the relative contributions of mechanics and neural control. Twenty-six infants and seven adults were studied. Video, force plate, and electrogoniometer data were collected. Belt speed of the treadmill, width of base, and limb length were manipulated in adults. Influences of unweighting and limb length were explored in infants. Infants tended to move diagonal limbs together (trot-like). Adults additionally moved ipsilateral limbs together (pace-like). At lower speeds, movements of the four limbs were more equally spaced in time, with no clear pairing of limbs. At higher speeds, running symmetrical gaits were never observed, although one adult galloped. Widening stance prevented adults from using the pace-like gait, whereas lengthening the hind limbs (hands-and-feet crawling) largely prevented the trot-like gait. Limb length and unweighting had no effect on coordination in infants. We conclude that human crawling shares features both with other primates and with nonprimate quadrupeds, suggesting similar underlying mechanisms. The greater restriction in coordination patterns used by infants suggests their nervous system has less flexibility.

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