Effect of Stretch on Formation and Conduction of Electrical Impulses in the Isolated Sinoauricular Chamber of Frog's Heart

1957 ◽  
Vol 192 (1) ◽  
pp. 111-113 ◽  
Author(s):  
C. L. Pathak
Keyword(s):  
Action Potential ◽  
Conduction Velocity ◽  
Perfusion Pressure ◽  
Intraluminal Pressure ◽  
Impulse Frequency ◽  
Electrical Impulse ◽  
Electrical Impulses

The influence of stretch due to increased intraluminal pressure on the formation and conduction of electrical impulse was studied electrocardiographically in 12 isolated sinoauricular chambers of frog hearts perfused with frogs' Ringer. The impulse frequency was found to be directly proportional to the degree of intraluminal perfusion pressure up to a certain critical head of pressure (2–6 cm Ringer), beyond which the impulse frequency declined. At higher pressures the electrogram showed a diminished amplitude of the action potential and broadening and notching of sinus waves and auricular complexes. The duration and conduction velocity of electrical impulse was increased.

Vasomotion and Contraction in the Perfused Mesenteric–Portal Vein: Effect of Drugs and Altered Perfusion Pressure

1971 ◽  
Vol 49 (6) ◽  
pp. 615-618 ◽  
Author(s):  
H. James Rhodes ◽  
M. C. Sutter
Keyword(s):  
Portal Vein ◽  
Perfusion Pressure ◽  
Splanchnic Circulation ◽  
Intraluminal Pressure ◽  
Longitudinal Tension ◽  
Portal Veins ◽  
Spontaneous Contractions

Isolated rabbit anterior mesenteric–portal veins (A.M.V.) which possess vasomotion were perfused with Kreb's solution in an apparatus designed so that intraluminal pressure and longitudinal tension could be measured simultaneously. The rate of vasomotion increased as perfusion pressure was increased from 0 to approximately 5 or 6 mm Hg. The amplitude of these spontaneous contractions increased to a maximum at a perfusion pressure of approximately 6 mm Hg and then decreased as perfusion pressure was raised further. Noradrenaline (10−7 g/ml) increased the longitudinal tension, but slightly decreased intraluminal pressure. Isopropylnoradrenaline (10−7 g/ml) had little effect on intraluminal pressure but decreased the amplitude of spontaneous contractions. It is suggested that the effect of perfusion pressure on the frequency and amplitude of vasomotion in the A.M.V. is related to autoregulation and that this perfused preparation may be a useful model for study of the rheology and responses to drugs of the splanchnic circulation.

Conduction Velocities and Their Temperature Coefficients in Sensory Nerve Fibres of Cockroach Legs

1967 ◽  
Vol 46 (1) ◽  
pp. 63-84
Author(s):  
K. M. CHAPMAN ◽  
J. H. PANKHURST
Keyword(s):  
Conduction Velocity ◽  
Periplaneta Americana ◽  
Sensory Nerve ◽  
Point Of View ◽  
Conduction Delay ◽  
Nerve Fibres ◽  
Impulse Frequency ◽  
Temperature Coefficients ◽  
Conduction Velocities ◽  
Sensory Encoding

1. Conduction velocities of individual afferent nerve fibres from tactile spines and proprioceptive campaniform sensilla have been measured in situ over the temperature range 5-42° C., in leg preparations of the cockroach Periplaneta americana. 2. Conduction velocities at 20° C. (u20) averaged 3.3±1.4 m./sec., ranging from 1.6 to 11.0 m./sec. 3. Temperature coefficients, expressed as Q10 for the interval 20-30° C., averaged 1.7±0.24, ranging from 1.3 to 2.6. 4. The length of the propagated disturbance is about 2-3 mm., and is nearly temperature-independent. 5. Fibre diameters, estimated from conduction velocity, must be about 10 µ. 6. There is no correlation between conduction velocity and distance from the sensillum to the thoracic ganglion. Conduction delays in fibres conducting within one standard deviation of mean u20 range from about 2 to 15 msec., from the most proximal to the most distal tactile spines. 7. The effect of conduction delay on temporal and spatial sensory encoding is probably unimportant from a behavioural point of view. It contributes a factor of the form exp(-sd/u) to the sensory transfer function, and may be appreciable at upper physiological frequencies of impulse frequency modulation.

scholarly journals Normal neurophysiologic parameters of the median nerve among adult healthy Sudanese population

2020 ◽  
Vol 10 (4) ◽  
pp. 136-141
Author(s):  
Mohammed Salah Elmagzoub ◽  
Ahmed Hassan Ahmed ◽  
Hussam M A Hameed
Keyword(s):  
Action Potential ◽  
Median Nerve ◽  
Conduction Velocity ◽  
Nerve Conduction ◽  
Compound Muscle Action Potential ◽  
Motor Nerve ◽  
Sensory Nerve ◽  
Peak Latency ◽  
Muscle Action Potential ◽  
Sensory Nerve Action

Background: Nerve conduction studies (NCSs) help in delineating the extent distribution of neural lesion, and the diagnosis of peripheral nerve disorders. Because normative nerve conduction parameters were not yet established in Sudan EMG laboratories, this study aims towards having our own reference values, as we are using the American and British parameters. This will allow avoiding the discrepancies that might be induced by many factors. Methods: NCSs were performed in 200 Median nerves of 100 adult healthy Sudanese subjects using standardized techniques. Results: The median SNAP (sensory nerve action potential) values were as follows: distal latency, 2.6±3 ms with a range of (2.3-2.9); peak latency, 3.5±0.5 ms (3.0-4.0); amplitude, 47.7±18.0μV (29.7-65.7); conduction velocity, 53.0±7.8 m/s (45.2-60.8). The following values were obtained for the Median nerve CMAP (compound muscle action potential) at wrist stimulation: distal latency, 3.5±0.5 ms with a range of (3.0-4.0); peak latency, 9.4± 1.0 ms (8.4-10.4); duration, 5.9±0.9 ms (5.0-6.8); amplitude, 12.3±2.5 mV (9.8-14.8); area, 43.0±10.4 mVms (32.6-53.4); conduction velocity, 63.6±6.2 m/s (57.4-69.8). The F wave was 28.4±1.8 ms (26.6-30.2). Conclusion: The overall mean sensory and motor nerve conduction parameters for the tested nerve compared favorably with the existing literature with some discrepancies that were justified.

scholarly journals Effect of pulsed high intensity focused ultrasound on the nerve compound action potential amplitude and conduction velocity

2021 ◽  
Author(s):  
Steve Tran
Keyword(s):  
Action Potential ◽  
Conduction Velocity ◽  
High Intensity ◽  
Focused Ultrasound ◽  
Compound Action Potential ◽  
Homarus Americanus ◽  
High Intensity Focused Ultrasound ◽  
Nerve Tissue ◽  
Nerve Function ◽  
Compound Action

Therapeutic HIFU has been used as a non-invasive energy modality to compromise nerve function since the 1950s. Several contributions have been made in recent years to characterize these effects on nerve function. In this study, short repeated bursts of HIFU, termed as pulsed high intensity focused ultrasound (pHIFU), was directed at nerve tissue. The pHIFU transducer operated at a central frequency of 1.95 MHz and had a focal length of approximately 12 cm. The ventral nerve cord from the American Lobster (Homarus americanus), n=15, was sonicated cumulatively at 3 exposure times: 1s, 6s, and 16s, at an intensity of 1010 W/cm2, or focal pressure of 5.51 MPa. The compound action potential (CAP) and conduction velocity (CV) were seen to decrease as sonication exposure time to the nerve increased. The experiments performed demonstrate the feasibility to modulate nerve CAP and nerve CV using non-thermal mechanisms of ultrasound.

Basic electrophysiological properties of spinal cord motoneurons during old age in the cat

1987 ◽  
Vol 58 (1) ◽  
pp. 180-194 ◽  
Author(s):  
F. R. Morales ◽  
P. A. Boxer ◽  
S. J. Fung ◽  
M. H. Chase
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Action Potential ◽  
Old Age ◽  
Conduction Velocity ◽  
Input Resistance ◽  
Action Potential Amplitude ◽  
Electrophysiological Properties ◽  
Potential Amplitude ◽  
Versus Input

1. The electrophysiological properties of alpha-motoneurons in old cats (14–15 yr) were compared with those of adult cats (1–3 yr). These properties were measured utilizing intracellular recording and stimulating techniques. 2. Unaltered in the old cat motoneurons were the membrane potential, action potential amplitude, and slopes of the initial segment (IS) and soma dendritic (SD) spikes, as well as the duration and amplitude of the action potential's afterhyperpolarization. 3. In contrast, the following changes in the electrophysiological properties of lumbar motoneurons were found in the old cats: a decrease in axonal conduction velocity, a shortening of the IS-SD delay, an increase in input resistance, and a decrease in rheobase. 4. In spite of these considerable changes in motoneuron properties in the old cat, normal correlations between different electrophysiological properties were maintained. The following key relationships, among others, were the same in adult and old cat motoneurons: membrane potential polarization versus action potential amplitude, duration of the afterhyperpolarization versus motor axon conduction velocity, and rheobase versus input conductance. 5. A review of the existing literature reveals that neither chronic spinal cord section nor deafferentation (13, 21) in adult animals produce the changes observed in old cats. Thus we consider it unlikely that a loss of synaptic contacts was responsible for the modifications in electrophysiological properties observed in old cat motoneurons. 6. We conclude that during old age there are significant changes in the soma-dendritic portion of cat motoneurons, as indicated by the modifications found in input resistance, rheobase, and IS-SD delay, as well as significant changes in their axons, as indicated by a decrease in conduction velocity.

Effects of octanol on canine subendocardial Purkinje-to-ventricular transmission

1985 ◽  
Vol 249 (6) ◽  
pp. H1228-H1231 ◽  
Author(s):  
R. W. Joyner ◽  
E. D. Overholt
Keyword(s):  
Action Potential ◽  
Conduction Velocity ◽  
Current Flow ◽  
Conduction Delay ◽  
Papillary Muscles ◽  
Maximal Rate ◽  
Gap Junctional ◽  
Junctional Resistance ◽  
P Cells

The effects of 0.2 mM octanol on action potential propagation were investigated using in vitro preparations of canine papillary muscles. In these preparations an action potential initiated in the superficial Purkinje (P) layer propagates across specific Purkinje-ventricular junction (PVJ) sites into the underlying ventricular (V) layer. The conduction delay at PVJ sites increased from 4.85 +/- 1.55 to 8.85 +/- 3.34 (mean +/- SD) ms (n = 10, P less than 0.005), an 82% increase. However, propagation within the V syncytium was much less affected, with a decrease of conduction velocity by only 10% and a decrease in the maximal rate of rise of the action potential of 23%. The results indicate that octanol, which has previously been shown to increase gap junctional resistance, has a preferential effect on PVJ sites, as predicted by the hypothesis that there is a restricted pathway for intracellular current flow from P cells to V cells at these sites.

Intracellular recording from pectoral fin motoneurons of the stingray Dasyatis sabina, an elasmobranch fish

1984 ◽  
Vol 51 (4) ◽  
pp. 666-679 ◽  
Author(s):  
B. J. Williams ◽  
M. H. Droge ◽  
R. B. Leonard
Keyword(s):  
Action Potential ◽  
Conduction Velocity ◽  
Initial Segment ◽  
Recurrent Events ◽  
Membrane Conductance ◽  
Membrane Resistance ◽  
Pectoral Fin ◽  
Dasyatis Sabina ◽  
Axonal Conduction ◽  
Input Conductance

Intracellular recordings were made from antidromically identified pectoral fin motoneurons in unanesthetized, decerebrate stingrays (Dasyatis sabina). These recordings had the three all-or-none components seen in other vertebrate motoneuron recordings. About 25% of the impalements had resting membrane potentials that were greater than -80 mV, which is larger than those of motoneurons from other vertebrate species. A novel depolarizing afterpotential (DAP) is associated with the isolated action potential occurring at the first node of Ranvier of the axon (M-spike). Occlusion experiments exclude recurrent events as the source of this potential. A capacitive source for the DAP is postulated. Using morphological and passive electrical data on motoneurons from previous studies, calculations of the passive decay of the nodal spike indicate that the membrane resistance of the initial segment is low and nearly equal to that of nodal membrane. The soma-dendritic (SD) spike is followed by a prominent, humped delayed depolarization (DD). The DD is temporally associated with the onset of the action potential produced by the initial segment (IS spike). Sources of the long-lasting period of repolarization recorded with the IS spike, which may underlie the DD, are postulated. The afterhyperpolarization (AHP) of stingray motoneurons tends to be shorter and smaller in amplitude than that of other vertebrate motoneurons. A negligible conductance change was often found during the period following an SD spike. No significant correlation was found between AHP duration and axonal conduction velocity. The input conductance of stingray motoneurons ranged between 1.5 X 10(-7) and 13.3 X 10(-7) S. The relationship between input conductance and axonal conduction velocity was determined from 42 motoneurons. These data were fitted by a power function with an exponent of 1.7, indicating that, in terms of membrane conductance properties, large stingray motoneurons are simply scaled-up versions of the small motoneurons.

Spike-triggered average torque and muscle fiber conduction velocity of low-threshold motor units following submaximal endurance contractions

2005 ◽  
Vol 98 (4) ◽  
pp. 1495-1502 ◽  
Author(s):  
Dario Farina ◽  
Lars Arendt-Nielsen ◽  
Thomas Graven-Nielsen
Keyword(s):  
Action Potential ◽  
Motor Unit ◽  
Conduction Velocity ◽  
Surface Potential ◽  
Muscle Fiber ◽  
Discharge Rate ◽  
Motor Units ◽  
Muscle Fiber Conduction Velocity ◽  
Sustained Contraction ◽  
Low Threshold

The motor unit twitch torque is modified by sustained contraction, but the association to changes in muscle fiber electrophysiological properties is not fully known. Thus twitch torque, muscle fiber conduction velocity, and action potential properties of single motor units were assessed in 11 subjects following an isometric submaximal contraction of the tibialis anterior muscle until endurance. The volunteers activated a target motor unit at the minimum discharge rate in eight 3-min-long contractions, three before and five after an isometric contraction at 40% of the maximal torque, sustained until endurance. Multichannel surface electromyogram signals and joint torque were averaged with the target motor unit potential as trigger. Discharge rate (mean ± SE, 6.6 ± 0.2 pulses/s) and interpulse interval variability (33.3 ± 7.0%) were not different in the eight contractions. Peak twitch torque and recruitment threshold increased significantly (93 ± 29 and 12 ± 5%, P < 0.05) in the contraction immediately after the endurance task with respect to the preendurance values (0.94 ± 0.26 mN·m and 3.7 ± 0.5% of the maximal torque), whereas time to peak of the twitch torque did not change (74.4 ± 10.1 ms). Muscle fiber conduction velocity decreased and action potential duration increased in the contraction after the endurance (6.3 ± 1.8 and 9.8 ± 1.8%, respectively, P < 0.05; preendurance values, 3.9 ± 0.2 m/s and 11.1 ± 0.8 ms), whereas the surface potential peak-to-peak amplitude did not change (27.1 ± 3.1 μV). There was no significant correlation between the relative changes in muscle fiber conduction velocity or surface potential duration and in peak twitch torque ( R2 = 0.04 and 0.10, respectively). In conclusion, modifications in peak twitch torque of low-threshold motor units with sustained contraction are mainly determined by mechanisms not related to changes in action potential shape and in its propagation velocity.

Sign in / Sign up

Export Citation Format

Share Document