scholarly journals Acidosis inhibits rhythmic contractions of human thoracic ducts

2019 ◽  
Vol 7 (8) ◽  
pp. e14074 ◽  
Author(s):  
Anders L. Moeller ◽  
Vibeke E. Hjortdal ◽  
Donna M. B. Boedtkjer ◽  
Ebbe Boedtkjer
Keyword(s):  
Rhythmic Contractions

Vasodilation contributes to the rapid hyperemia with rhythmic contractions in humans

1998 ◽  
Vol 76 (4) ◽  
pp. 418-427 ◽  
Author(s):  
J K Shoemaker ◽  
M E Tschakovsky ◽  
R L Hughson
Keyword(s):  
Blood Flow ◽  
Forearm Blood Flow ◽  
Perfusion Pressure ◽  
Blood Velocity ◽  
Pulsed Doppler ◽  
Contraction Rate ◽  
Handgrip Exercise ◽  
Arterial Diameter ◽  
Exercise Tests ◽  
Rhythmic Contractions

The hypothesis that the rapid increases in blood flow at the exercise onsetare exclusively due to the mechanical effects of the muscle pump was tested in six volunteersduring dynamic handgrip exercise. While supine, each subject completed a series of eightdifferent exercise tests in which brachial artery blood pressure (BP) was altered by25–30 mmHg (1 mmHg = 133.3 Pa) by positioning the arm above or below the heart.Two different weights, corresponding to 4.9 and 9.7% of maximal voluntary isometriccontraction, were raised and lowered at two different contraction rate schedules (1s:1s and 2s:2swork–rest) each with a 50% duty cycle. Beat-by-beat measures of mean blood velocity (MBV)(pulsed Doppler) were obtained at rest and for 5 min following step increases in work ratewith emphasis on the first 24 s. MBV was increased 50–100% above rest following the firstcontraction in both arm positions (p < 0.05). The increase in MBV from rest was greaterin the below position compared with above, and this effect was observed following the first andsubsequent contractions (p < 0.05). However, the positional effect on the increase inMBV could not be explained entirely by the ~40% greater BP in this position. Also, the greaterworkload resulted in greater increases in MBV as early as the first contraction, compared withthe light workload (p < 0.05) despite similar reductions in forearm volume followingsingle contractions. MBV was greater with faster contraction rate tests by 8 s of exercise. Itwas concluded that microvascular vasodilation must act in concert with a reduction in venouspressure to increase forearm blood flow within the initial 2–4 s of exercise.Key words: Doppler, mean blood velocity, arterial diameter,handgrip exercise, perfusion pressure.

Effect of lung volume on breath holding

1987 ◽  
Vol 62 (5) ◽  
pp. 1962-1969 ◽  
Author(s):  
W. A. Whitelaw ◽  
B. McBride ◽  
G. T. Ford
Keyword(s):  
Lung Volume ◽  
Hold Time ◽  
Esophageal Pressure ◽  
Breath Holding ◽  
Breath Hold ◽  
Pressure Waves ◽  
Expiratory Muscle ◽  
Inspiratory Muscles ◽  
Consistent Change ◽  
Rhythmic Contractions

The mechanism by which large lung volume lessens the discomfort of breath holding and prolongs breath-hold time was studied by analyzing the pressure waves made by diaphragm contractions during breath holds at various lung volumes. Subjects rebreathed a mixture of 8% CO2–92% O2 and commenced breath holding after reaching an alveolar plateau. At all volumes, regular rhythmic contractions of inspiratory muscles, followed by means of gastric and pleural pressures, increased in amplitude and frequency until the breakpoint. Expiratory muscle activity was more prominent in some subjects than others, and increased through each breath hold. Increasing lung volume caused a delay in onset and a decrease in frequency of contractions with no consistent change in duty cycle and a decline in magnitude of esophageal pressure swings that could be accounted for by force-length and geometric properties. The effect of lung volume on the timing of contractions most resembled that of a chest wall reflex and is consistent with the hypothesis that the contractions are a major source of dyspnea in breath holding.

Microscale Flow Pumping Inspired by Rhythmic Tracheal Compressions in Insects

2011 ◽  
Author(s):  
Yasser Aboelkassem ◽  
Anne E. Staples ◽  
John J. Socha
Keyword(s):  
Tracheal Tube ◽  
Incompressible Flows ◽  
Time Lag ◽  
Viscous Effects ◽  
Single Cycle ◽  
Single Model ◽  
Microscale Flow ◽  
Valveless Pumping ◽  
Viscous Incompressible Flows ◽  
Rhythmic Contractions

Inspired by the physiological network of insects, which have dimensions on the order of micrometers to millimeters, we study the airflow within a single model insect tracheal tube. The tube undergoes localized rhythmic wall contractions. A theoretical analysis is given to model the airflow within the tracheal tube. Since flow motions at the microscale are dominated mainly by viscous effects, and the tube has radius, R, that is much smaller than its length, L, (i.e. δ = R/L ≪ 1), lubrication theory for axisymmetric, viscous, incompressible flows at low Reynolds number (Re ∼ δ) is used to model the problem mathematically. Expressions for the velocity field, pressure gradient, wall shear stress and net flow produced by the driving tube wall contractions are derived. The effect of the contraction amplitudes, time lag, and spacing between two sequences of contractions on the time-averaged net flow over a single cycle of wall motions is investigated. The study presents a new, insect-inspired mechanism for valveless pumping that can guide efforts to fabricate novel microfluidic devices that mimic these physiological systems. A x-ray image that shows the tracheal network of the respiratory system of an insect (Carabid beetle) and the associated locations of these rhythmic contractions are shown in figure (1) to promote this study.

The Renal Pelvis: Machinery That Concentrates Urine in the Papilla

Physiology ◽  
2003 ◽  
Vol 18 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Terry M. Dwyer ◽  
Bodil Schmidt-Nielsen
Keyword(s):  
Renal Pelvis ◽  
Collecting Duct ◽  
Osmotic Gradient ◽  
Elastic Recoil ◽  
Vasa Recta ◽  
Rhythmic Contractions

Two decades ago, Bodil Schmidt-Nielsen and Bruce Graves documented the rhythmic contractions of the renal pelvis in a remarkable video, visually demonstrating how peristaltic waves empty the papilla and how the subsequent elastic recoil draws water from the collecting duct and into the tethered-open ascending vasa recta. Thus a periodic hydrostatic gradient generates an axial osmotic gradient. This review recapitulates the video and offers a link to figures and scenes digitized from the original tape.

scholarly journals Primary and secondary motoneurons use different calcium channel types to control escape and swimming behaviors in zebrafish

2020 ◽  
Author(s):  
Hua Wen ◽  
Kazumi Eckenstein ◽  
Vivien Weihrauch ◽  
Christian Stigloher ◽  
Paul Brehm
Keyword(s):  
Calcium Channels ◽  
Calcium Channel ◽  
Muscle Cell ◽  
Transmitter Release ◽  
Escape Response ◽  
Quantal Content ◽  
Release Probability ◽  
High Release ◽  
Postsynaptic Cell ◽  
Rhythmic Contractions

AbstractThe escape response and rhythmic swimming in zebrafish are distinct behaviors mediated by two functionally distinct motoneuron (Mn) types. The primary (1°Mn) type depresses, has a large quantal content (Qc), and a high release probability (Pr). Conversely, the secondary (2°Mn) type facilitates and has low and variable Qc and Pr. This functional duality matches well the distinct associated behaviors, with the 1°Mn providing the strong, singular C-bend initiating escape and the 2°Mn confers weaker, rhythmic contractions. Contributing to these functional distinctions is our identification of P/Q type calcium channels mediating transmitter release in 1°Mns and N type channels in 2°Mns. Remarkably, despite these functional and behavioral distinctions, all ~15 individual synapses on each muscle cell are shared by a 1°Mn bouton and at least one 2°Mn bouton. This novel blueprint of synaptic sharing provides an efficient way of controlling two different behaviors at the level of a single postsynaptic cell.

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