Effects of current flow on pacemaker activity of the isolated kitten sinoatrial node

1980 ◽  
Vol 238 (3) ◽  
pp. H307-H316 ◽  
Author(s):  
J. Jalife ◽  
A. J. Hamilton ◽  
V. R. Lamanna ◽  
G. K. Moe
Keyword(s):  
Response Curve ◽  
Current Flow ◽  
Sinoatrial Node ◽  
Phase Response Curve ◽  
Vagal Stimulation ◽  
Cardiac Pacemaker ◽  
Phase Response ◽  
Pacemaker Activity ◽  
Current Pulses ◽  
Sucrose Gap

The dynamic behavior of the cardiac pacemaker in response to single or to periodically repeated perturbations was studied using kitten sinoatrial (SA) nodal strips mounted in a sucrose gap. Sustained stepwise applications of current across the gap produce lasting variations in pacemaker cycle length that depend on current magnitude and polarity, but not on the phase of the pacemaker period at the time of the input. Brief current pulses, whether hyperpolarizing or depolarizing, may abbreviate or prolong the immediately affected cycle depending on their timing. These changes result in phase shifts of the subsequent discharges, but they do not alter the pacemaker period permanently. The phasic effects of brief current pulses can be described by a phase response curve (PRC), which is a plot of the phase shift as a function of the position of the stimulus in the pacemaker cycle. PRCs were constructed for inputs of different polarity and several strengths and durations. The behavior of the sinus nodal pacemaker when interacting with period perturbing inputs, such as vagal stimulation or electrotonic depolarization, can be predicted on the basis of the phase response curve.

Synchronization of automatic cells in S-A node during vagal stimulation in dogs

1984 ◽  
Vol 246 (4) ◽  
pp. H585-H591 ◽  
Author(s):  
T. Yang ◽  
M. D. Jacobstein ◽  
M. N. Levy
Keyword(s):  
Response Curve ◽  
Cardiac Cycle ◽  
Phase Response Curve ◽  
Vagal Stimulation ◽  
Nerve Fibers ◽  
Phase Response ◽  
Vagal Activity ◽  
Maximum Phase ◽  
The Right ◽  
Phase Differences

In anesthetized, open-chest dogs, one burst of stimuli was delivered to the left or right vagus nerve each cardiac cycle. The timing of the stimulus bursts relative to the cardiac cycle was varied by a constant, small amount on successive cardiac cycles, until the entire cardiac cycle was scanned. The level of vagal activity was changed by varying the number of stimulus pulses in each burst; two levels of activity were used in each experiment. For a given level of vagal activity, the mean cardiac cycle length and the amplitude of the phase-response curve were significantly greater during right than during left vagal stimulation. These response characteristics increased as the level of vagal activity was augmented. The minimum-to-maximum phase differences of the phase-response curve were less during right than during left vagal stimulation and when the level of vagal activity was increased. The disparities between the minimum-to-maximum phase differences for the right and left vagi are probably ascribable to the associated differences in the overall magnitudes of the chronotropic responses, rather than to any fundamental difference in the innervation of the effector cells by nerve fibers originating from the right and left sides.

Phase Response Curve for the Ultradian Rhythm of the Lateral Leaflets of Desmodium gyrans Using DC Current Pulses

2001 ◽  
Vol 56 (1-2) ◽  
pp. 77-81 ◽  
Author(s):  
Vijay Kumar Sharma ◽  
Christer Jensen ◽  
Anders Johnsson
Keyword(s):  
Response Curve ◽  
Phase Response Curve ◽  
Phase Shifts ◽  
Phase Response ◽  
Ultradian Rhythm ◽  
Leaf Movement ◽  
Current Pulses ◽  
Dc Current

Abstract In the present study the leaf movement rhythm was perturbed by the application of DC current pulses 15 μA, 10 seconds, voltage applied: 10 V) to the upper part of the pulvinus, passing through the pulvinus and its stalk. The pulses were applied at four different positions of the leaflets: when the leaves were at the lowermost position, when moving up, at the uppermost position and when moving down. The pre-perturbed and the post-perturbed rhythms were compared. We found that the rhythms were shifted in phase and the phase shifts observed at the four different positions of the leaflets were significantly different in magnitude as well as direction. Furthermore, we could also observe phase advances, which is in contrast to an earlier finding. A phase response curve (PRC) was constructed to illustrate the sensitivity of the oscillating leaflet system to DC pulses. Substantial delays of about 50 s (as compared to the period of about 200 s) were obtained when pulses were administered at the lowermost position and when leaflet were moving upwards, while advances or no phase shifts were recorded in the uppermost position and when leaflet were moving down respectively.

Synchronization of two coupled pacemaker cells based on the phase response curve

2009 ◽  
Vol 4 (1) ◽  
pp. 57-66
Author(s):  
Hossein Gholizade-Narm ◽  
Asad Azemi ◽  
Morteza Khademi ◽  
Masoud Karimi-Ghartemani
Keyword(s):  
Response Curve ◽  
Phase Response Curve ◽  
Phase Response ◽  
Pacemaker Cells

Light effects on circadian timing system of a diurnal primate, the squirrel monkey

1985 ◽  
Vol 249 (2) ◽  
pp. R274-R280 ◽  
Author(s):  
T. M. Hoban ◽  
F. M. Sulzman
Keyword(s):  
Squirrel Monkey ◽  
Response Curve ◽  
Phase Response Curve ◽  
Phase Response ◽  
Day Length ◽  
Circadian Timing ◽  
Subjective Night ◽  
Timing System ◽  
Circadian Timing System ◽  
Light Effects

We examined light effects on the circadian timing system of the squirrel monkey. A phase-response curve to 1-h pulses of light was constructed for the drinking rhythm of six animals. The phase-response curve was the same type as that exhibited by nocturnal rodents, with phase delays occurring early in the subjective night and phase advances late in the subjective night. The range of entrainment of 10 monkeys to days with 1 h light and x h dark was determined. Five monkeys used to generate the phase-response curve were also used in the range of entrainment determination. For short light-dark cycles the range of entrainment was smaller than that expected, with no monkey entraining to a day length of less than 23.5 h.

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