Respiration-dependent Movements of the Column of Stylidium gvaminifolium

1981 ◽  
Vol 8 (1) ◽  
pp. 45 ◽  
Author(s):  
G.P Findlay ◽  
N Findlay
Keyword(s):  
Refractory Period ◽  
Angular Displacement ◽  
Metabolic Energy ◽  
Original Position ◽  
Firing Process ◽  
Mechanical Stimuli ◽  
Anaerobic Conditions ◽  
Absolute Refractory Period ◽  
Refractory Periods ◽  
Graded Responses

The column of the trigger plant, Stylidium graminifolium, when fully set responds to mechanical stimuli by flipping through an angle of about 4 radians in a fast firing movement lasting about 15-30 ms, and then slowly resetting to its original position in about 400 s. After resetting there is an absolute refractory period of about 500 s during which no further response to stimuli can be initiated, followed by a relative refractory period when graded responses increasing in rate and magnitude with time can be obtained. The resetting movement and the process, occurring during the refractory period, allowing subsequent firing to occur, are inhibited when the air surrounding the column is replaced by nitrogen. The firing movement, however, is not affected by these anaerobic conditions. Thus the firing movement is caused by passive physical forces, rapidly utilizing potential energy from a store built up during the previous resetting and refractory periods. Removal of the labellum, which the column touches when set, causes the column to oscillate with amplitude of about 3-3.5 radians and period of 1-2 ks. When the column is held at a constant angular displacement it develops an oscillatory torque with similar period. These oscillations are inhibited at all stages of the cycle by anaerobic conditions. It appears that the oscillatory behaviour is not a slowed-down firing process followed by normal resetting, but is linked throughout the cycle to the metabolic energy supply.

Control of colonic motility using electrical stimulation to modulate enteric neural activity

2021 ◽  
Author(s):  
Bradley Barth ◽  
Lee Travis ◽  
Nick J Spencer ◽  
Warren M. Grill
Keyword(s):  
Electrical Stimulation ◽  
Refractory Period ◽  
Colonic Motility ◽  
Gastrointestinal Transit ◽  
Absolute Refractory Period ◽  
Refractory Periods ◽  
Colonic Motor ◽  
The Mean ◽  
Insight Into

Electrical stimulation of the enteric nervous system (ENS) is an attractive approach to modify gastrointestinal transit. Colonic motor complexes (CMCs) occur with a periodic rhythm, but the ability to elicit a premature CMC depends, at least in part, upon the intrinsic refractory properties of the ENS, which are presently unknown. The objectives of this study were to record myoelectric complexes (MCs, the electrical correlates of CMCs) in the smooth muscle and (i) determine the refractory periods of MCs, (ii) inform and evaluate closed-loop stimulation to repetitively evoke MCs, and (iii) identify stimulation methods to suppress MC propagation. We dissected the colon from male and female C57BL/6 mice, preserving the integrity of intrinsic circuitry while removing the extrinsic nerves, and measured properties of spontaneous and evoked MCs in vitro. Hexamethonium abolished spontaneous and evoked MCs, confirming the necessary involvement of the ENS for electrically-evoked MCs. Electrical stimulation reduced the mean interval between evoked and spontaneous CMCs (24.6 ± 3.5 vs 70.6 ± 15.7 s, p = 0.0002, n = 7). The absolute refractory period was 4.3 s (95% CI = 2.8 - 5.7 s, R2 = 0.7315, n = 8). Electrical stimulation applied during fluid distention-evoked MCs led to an arrest of MC propagation, and following stimulation, MC propagation resumed at an increased velocity (n = 9). The timing parameters of electrical stimulation increased the rate of evoked MCs and the duration of entrainment of MCs, and the refractory period provides insight into timing considerations for designing neuromodulation strategies to treat colonic dysmotility.

Effects of infarction, procainamide, coupling interval, and cycle length on refractoriness of extrastimuli

1985 ◽  
Vol 248 (5) ◽  
pp. H606-H613
Author(s):  
F. E. Marchlinski ◽  
M. E. Cain ◽  
R. A. Falcone ◽  
R. F. Corky ◽  
J. F. Spear ◽  
...  
Keyword(s):  
Refractory Period ◽  
Cycle Length ◽  
Narrow Range ◽  
Left Ventricular ◽  
Effective Refractory Period ◽  
Stimulation Site ◽  
Refractory Periods ◽  
Coupling Interval ◽  
Cycle Lengths ◽  
Site Of Stimulation

The effects of prematurity, cycle length, site of stimulation, and procainamide on ventricular refractoriness following an extrastimulus (S2) were assessed in 10 dogs with and 10 dogs without infarction. Extrastimuli were introduced at preselected coupling intervals (S1-S2) from normal right and left ventricular sites and from left ventricular sites of infarction during drive cycle lengths (S1-S1) of 350 and 250 ms. At each S1-S2 interval, the effective refractory period of S2 was determined by introducing a second extrastimulus (S3). At all stimulation sites, cycle lengths, and before and during infusion of procainamide (mean concn 18.6 +/- 3.5 micrograms/ml), shortening (greater than 10 ms change) in refractoriness was most marked over a narrow range of closely coupled S1-S2 intervals. Regardless of stimulation site, the effective refractory period of S2 was less during a cycle length of 250 ms compared with a cycle length of 350 ms. In dogs without infarction, the effective refractory periods of S2 from left ventricular sites tended to be longer than from right ventricular sites, particularly during procainamide administration. The refractory period of S2 at sites of infarction did not differ consistently from those at normal sites. Finally, at all stimulation sites and cycle lengths, procainamide prolonged refractoriness of S2 at each S1-S2 interval and blunted the total shortening in refractoriness in response to S2.

The Time Course of Preparation*

1967 ◽  
Vol 19 (3) ◽  
pp. 272-279 ◽  
Author(s):  
Paul Bertelson
Keyword(s):  
Visual Stimulus ◽  
Refractory Period ◽  
Time Course ◽  
Reaction Times ◽  
Warning Signal ◽  
High Time ◽  
Refractory Periods ◽  
Time Uncertainty ◽  
Order Of Magnitude ◽  
Choice Reaction Times

The time course of the adjustments triggered by a warning signal was studied by measuring choice reaction times (RTs) at different predictable foreperiods after such a signal. Before the warning signal, a high time uncertainty situation was created by imposing either a long constant foreperiod of 5 sec. or one varying in the range 1.5 to 5 sec. The warning signal was a click. Foreperiods ranging from 0 to 300 millisec. were used in different blocks of trials. The stimulus was the onset of one of two lamps calling for the pressing of one of two keys. A control condition, without click, was used also. RTs were found to decrease continuously when the forperiod was increased from 0 to 100-150 millisec. The click delivered simultaneously with the stimulus permitted reactions significantly faster than in the control condition. It is concluded (a) that the latency of preparation can be much shorter than the 2 to 4 sec. reported by Woodrow; (b) that the warning signal can be used as a time cue to start preparatory adjustments without starting a refractory period of the order of magnitude found in experiments with pairs of successive reactions, and thus that such refractory periods are not the inevitable cost of paying attention to a signal. There is also some suggestion that in this situation the click not only triggers preparatory adjustments, but also causes an immediate facilitation of the reaction to the visual stimulus.

EFFECT OF TESTOSTERONE ON NEURONAL REFRACTORY PERIODS, SEXUAL BEHAVIOUR AND LUTEINIZING HORMONE: A COMPARISON OF TIME-COURSES

1981 ◽  
Vol 89 (1) ◽  
pp. 147-155 ◽  
Author(s):  
K. M. KENDRICK ◽  
R. F. DREWETT ◽  
C. A. WILSON
Keyword(s):  
Luteinizing Hormone ◽  
Sexual Behaviour ◽  
Plasma Levels ◽  
Refractory Period ◽  
Testosterone Propionate ◽  
Stria Terminalis ◽  
Refractory Periods ◽  
Sexual Responses ◽  
Time Courses

Measurements of the refractory period of stria terminalis neurones that are sensitive to testosterone propionate, of sexual behaviour and of plasma levels of LH were taken in castrated rats at various times after initiation of treatment with testosterone propionate. Levels of LH dropped within 24 h, before there was any change in neuronal refractory periods. The period of latency to mounting, however, was reduced to its shortest only after 7–8 days and ejaculations first occurred at the same time; these sexual responses correlated in time with the reduction of the neuronal refractory period to its lowest level.

scholarly journals Inotropic Effects of Trains of Impulses Applied during the Contraction of Cardiac Muscle

1960 ◽  
Vol 44 (2) ◽  
pp. 415-432 ◽  
Author(s):  
A. J. Brady ◽  
B. C. Abbott ◽  
W. F. H. M. Mommaerts
Keyword(s):  
Cell Membrane ◽  
Cardiac Muscle ◽  
Direct Effect ◽  
Refractory Period ◽  
Muscle Preparation ◽  
Inotropic Effects ◽  
Absolute Refractory Period ◽  
The Absolute ◽  
Stimulation Of

The application of a train of supramaximal stimuli during the absolute refractory period of a cardiac muscle preparation has two effects: a depression of the contraction during which it is applied, and a large potentiation of subsequent contractions. The former is ascribed to a direct effect upon the cell membrane, and is an indication of the continued control of the contractile event by this membrane. The latter is explained as a sudden liberation of norepinephrine by a stimulation of embedded nerve elements, which norepinephrine then distributes itself through the tissue and finally diffuses away.

scholarly journals Studies on the Accumulation of Putrescine and Spermidine in Escherichia coli

1985 ◽  
Vol 38 (4) ◽  
pp. 383
Author(s):  
AJ Smigielski ◽  
ME Muir ◽  
BJ Wallace
Keyword(s):  
High Energy ◽  
Proton Motive Force ◽  
Metabolic Energy ◽  
Uptake System ◽  
Anaerobic Conditions ◽  
High Dilution ◽  
E Coli ◽  
Chemostat Cultures ◽  
Slow Growing ◽  
Rate Of Accumulation

The rate of accumulation of the polyamines spermidine and putrescine by E. coli depended on growth rate. Spermidine ac~umulation was faster in chemostat cultures with high dilution rates than in those with low dilution rates and was slower in bacteria that had been grown for several generations with either putrescine or spermidine, suggesting that the spermidine-uptake system was repressed by exogenous polyamines. The uptake of spermidine required metabolic energy. Thus accumulation occurred in an energy-starved unc strain only upon addition of glucose (or D-lactate to a smaller extent). With glucose present accumulation occurred in an unc, frd strain under anaerobic conditions, suggesting that ATP drives uptake. However, accumulation was generally sensitive to carbonylcyanide m-chlorophenylhydrazone (CCCP), indicating that the proton motive force was involved in uptake. Unlike spermidine, putrescine accumulation was faster in slow-growing than in fast-growing cultures. This may have been due to greater efflux of putrescine at faster growth rates. Accumulation of putrescine was faster following prolonged growth with either putrescine or spermidine, suggesting induction of the putrescine-uptake system by exogenous polyamines. Like spermidine accumulation, putrescine accumulation required metabolic energy. Accumulation was insensitive to CCCP and occurred only when glucose was added to energy-starved unc bacteria, suggesting that high-energy bonds may drive the uptake of putrescine.

Influence of Cycle Length Upon Refractory Period of Auricles, Ventricles, and A-V Node in the Dog

1956 ◽  
Vol 184 (2) ◽  
pp. 287-295 ◽  
Author(s):  
Carlos Mendez ◽  
Carl C. Gruhzit ◽  
Gordon K. Moe
Keyword(s):  
Refractory Period ◽  
Cycle Length ◽  
Cumulative Effect ◽  
Transmission System ◽  
Ventricular Muscle ◽  
Dog Heart ◽  
Refractory Periods ◽  
Premature Beats

The functional refractory periods (FRP) of auricular and ventricular muscle, and of the A-V transmission system were estimated in the denervated dog heart. In all three tissues the FRP was found to be a curvilinear function of the immediately preceding cycle length, with values for all but very early premature beats falling close to the curve describing the basic cycles; that is, there was no evidence for a cumulative effect of frequency. In the auricle, the FRP of even the earliest possible premature beats appeared to fit the curve relating cycle length to refractory period. In both the A-V node and ventricles very early responses deviated from an otherwise smooth relationship. It is postulated that the deviations may represent dissociation of the properties of two different elements in each of these tissues.

Sign in / Sign up

Export Citation Format

Share Document