scholarly journals The effect of cellular energy reserves and internal calcium ions on the potassium conductance in skeletal muscle of the frog.

1983 ◽  
Vol 336 (1) ◽  
pp. 211-228 ◽  
Author(s):  
R Fink ◽  
S Hase ◽  
H C Lüttgau ◽  
E Wettwer
Keyword(s):  
Skeletal Muscle ◽  
Calcium Ions ◽  
Potassium Conductance ◽  
Energy Reserves ◽  
Cellular Energy ◽  
Internal Calcium

Nitrendipine blocks high potassium contractures but not twitches in rat skeletal muscle

1988 ◽  
Vol 66 (9) ◽  
pp. 1210-1213 ◽  
Author(s):  
G. B. Frank ◽  
L. Konya ◽  
T. Subrahmanyam Sudha
Keyword(s):  
Skeletal Muscle ◽  
Calcium Ions ◽  
Calcium Uptake ◽  
Channel Blocker ◽  
Mechanical Response ◽  
Extracellular Calcium ◽  
The Other ◽  
Rat Skeletal Muscle ◽  
Potassium Depolarization ◽  
High Potassium

The effects of the organic calcium channel blocker nitrendipine was tested on electrically evoked twitches and on potassium depolarization-induced contractures of rat lumbricalis muscles. Nitrendipine (10−7 to 5 × 10−5 M) blocked only the potassium contractures. It was concluded that blocking calcium uptake through the slow voltage-senstitive calcium channels during potassium depolarization blocks the mechanical response of the muscle. Thus extracellular calcium ions are required for the excitation–contraction (E–C) coupling during depolarization contractures. On the other hand, electrically evoked twitches were not affected by nitrendipine; therefore, extracellular calcium ions entering via the slow voltage-sensitive channels are not required for E–C coupling during the twitch.

scholarly journals Using lectures to identify student misconceptions: a study on the paradoxical effects of hyperkalemia on vascular smooth muscle

2020 ◽  
Vol 44 (1) ◽  
pp. 15-20
Author(s):  
Stephen J. Bordes ◽  
Jason Gandhi ◽  
Blake Bauer ◽  
Matthew Protas ◽  
Nadia Solomon ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Medical Students ◽  
Potassium Conductance ◽  
Equilibrium Potential ◽  
Control Mechanisms ◽  
Student Misconceptions ◽  
Clinical Scenarios ◽  
Paradoxical Effects ◽  
Muscle Types

Medical students have difficulty understanding the mechanisms underlying hyperkalemia-mediated local control of blood flow. Such control mechanisms are crucial in the brain, kidney, and skeletal muscle vasculature. We aimed to identify medical students’ misconceptions via assessment of students’ in-class knowledge and, subsequently, improve future teaching of this concept. In-class polling was performed with the TurningPoint clicker response system ( n = 860) to gauge students’ understanding of three physiological concepts related to hyperkalemia: membrane potential ( Vm), conductance, and smooth muscle response. Vm includes the concepts of equilibrium potential ( Veq) for specific ions, as well as driving force (DF =  Vm − Veq). Students understood the concept of DF (~70% answered correctly), suggesting their understanding of Vm. However, students misunderstood that hyperkalemia results in depolarization (~52% answered correctly) and leads to an increase in potassium conductance (~31% answered correctly). Clarification of the type of smooth muscle as vascular increased the percentage of correct responses (~51 to 73%). The data indicate that students lacked knowledge of specific potassium conductance in various muscle types, resulting in divergent responses, such as the canonical depolarization in skeletal muscle versus hyperpolarization in smooth muscle cells during hyperkalemia. Misunderstanding of this crucial concept of conductance is directly related to the students’ performance. Furthermore, we connected the paradoxical effect of hyperkalemia to pathological acute and chronic hyperkalemia clinical scenarios.

scholarly journals ADENOSINE TRIPHOSPHATE-LINKED CONCENTRATION OF CALCIUM IONS IN A PARTICULATE FRACTION OF RABBIT MUSCLE

1962 ◽  
Vol 14 (3) ◽  
pp. 389-400 ◽  
Author(s):  
Setsuro Ebashi ◽  
Fritz Lipmann
Keyword(s):  
Skeletal Muscle ◽  
Endoplasmic Reticulum ◽  
Electron Micrographs ◽  
Calcium Ions ◽  
Calcium Ion ◽  
Membrane Fraction ◽  
Ion Concentration ◽  
Rabbit Muscle ◽  
Differential Centrifugation ◽  
Calcium Ion Concentration

ATPase and ATP-dependent calcium ion concentration was studied with a membrane fraction isolated from homogenized rabbit skeletal muscle by differential centrifugation. Electron micrographs of the fraction indicate that it consists mainly of resealed tubules and vesicles of the endoplasmic reticulum. The up-to-1400-fold concentration of calcium in this fraction might be explained by proposing the existence of an energy-requiring system for the transport of calcium ions into the tubules or vesicles.

Development of membrane conductance of chick skeletal muscle in culture

1980 ◽  
Vol 58 (6) ◽  
pp. 600-605 ◽  
Author(s):  
C. M. Thomson ◽  
W. F. Dryden
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Initial Level ◽  
Potassium Conductance ◽  
Membrane Conductance ◽  
Resting Membrane Potential ◽  
Membrane Conductances ◽  
Rapid Changes ◽  
Fibre Development

Resting membrane potentials and membrane conductances of chick skeletal muscle in culture were determined from the 3rd to the 10th day after plating. The effect of tetraethylammonium (TEA) and of replacement of potassium with caesium on these parameters was investigated. Resting membrane potential (Em) rises during myogenesis in vitro and resting membrane conductance (Gm) falls. The initial level of Gm was relatively high (1.2 mS cm−2) but this fell to a final level around 0.2 mS cm−2. The most rapid changes in both parameters occurred between days 3 and 5 of culture. Both TEA and caesium depressed Em and Gm at all stages of development. On the 3rd day of culture Gm was reduced by 0.2 mS cm−2 by both agents. Thereafter, Gm was depressed by about 0.1 mS cm−2. Caesium does not penetrate potassium channels and the reduction in Gm is attributed to block of these channels. This indicates that resting potassium conductance is relatively constant at 0.1 mS cm−2 throughout muscle fibre development. Because TEA produces changes in Gm similar to those produced by caesium, TEA is concluded to be acting at the potassium channel in a manner similar to caesium.

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