scholarly journals Potassium conductance changes in skeletal muscle and the potassium concentration in the transverse tubules

1972 ◽  
Vol 225 (1) ◽  
pp. 33-56 ◽  
Author(s):  
W. Almers
Keyword(s):  
Skeletal Muscle ◽  
Potassium Concentration ◽  
Potassium Conductance ◽  
Transverse Tubules ◽  
Conductance Changes

scholarly journals ATP-energized Ca2+ pump in isolated transverse tubules of skeletal muscle.

1980 ◽  
Vol 255 (13) ◽  
pp. 6290-6298 ◽  
Author(s):  
N.R. Brandt ◽  
A.H. Caswell ◽  
J.P. Brunschwig
Keyword(s):  
Skeletal Muscle ◽  
Transverse Tubules

The Threshold for Potassium-Induced Contractures of Frog Skeletal Muscle. Potentiation of Potassium-Induced Contractures by Preexposure to Subthreshold Potassium Concentrations

1972 ◽  
Vol 50 (1) ◽  
pp. 37-44 ◽  
Author(s):  
E. C. Vos ◽  
G. B. Frank
Keyword(s):  
Skeletal Muscle ◽  
Potassium Concentration ◽  
Ringer Solution ◽  
Frog Skeletal Muscle ◽  
Contractile Apparatus ◽  
Tension Development ◽  
Eventual Loss ◽  
Active Processes ◽  
Muscle Potentiation ◽  
Small Bundle

A brief exposure (about 10–30 s) of a frog's toe muscle or a small bundle of fibers from the semi-tendinosus muscle to just subthreshold potassium concentrations potentiated contractures subsequently produced by exposing the muscles to a potassium concentration slightly above the threshold. The contractures thus potentiated had greater maximum tensions, and greater rates of tension development and relaxation than control contractures elicited by the same final potassium concentration. The resistance to stretch (R.T.S.) in the first few seconds of the potentiated contractures was about twice that of control contractures. Maximum potentiation occurred with preexposures of about 30 s; longer preexposures led to a decrease of potentiation and eventually to a depression of the contracture. The potentiation was not immediately abolished when the muscle was reexposed to Ringer solution but persisted for 2 min or longer (the 'washout effect'). It was concluded that exposing a muscle to low subcontracture threshold concentrations of potassium for a few seconds primes the intracellular contractile apparatus, probably by causing an increased sarcoplasmic concentration of Ca2+ ions, resulting in a potentiation of subsequently induced submaximal potassium contractures. The increase in metabolism (or 'Solandt effect') seen under these conditions is temporally related to the decline and eventual loss of the potentiation and is probably a reflection of active processes involved in reducing the sarcoplasmic concentration of Ca2+ ions.

scholarly journals The Intracellular Site of Calcium Activation of Contraction in Frog Skeletal Muscle

1970 ◽  
Vol 55 (1) ◽  
pp. 77-88 ◽  
Author(s):  
Saul Winegrad
Keyword(s):  
Skeletal Muscle ◽  
Room Temperature ◽  
Half Time ◽  
Frog Skeletal Muscle ◽  
Calcium Efflux ◽  
Transverse Tubules ◽  
Calcium Activation ◽  
Thin Filaments ◽  
Almost All ◽  
Terminal Cisternae

Radioautography has been used to localize 45Ca in isotopically labeled frog skeletal muscle fibers which had been quickly frozen during a maintained tetanus, a declining tetanus, or during the period immediately following a tetanus or a contracture. During a tetanus almost all of the myofibrillar 45Ca is localized in the region of the sarcomere occupied by the thin filaments. The amount varies with the tension being developed by the muscle. The movement of calcium within the reticulum from the tubular portion to the terminal cisternae during the posttetanic period has a half-time of about 9 sec at room temperature and a Q10 of about 1.7. Repolarization is not necessary for this movement. Evidence is given to support the notion that most calcium efflux from the cell occurs from the terminal cisternae into the transverse tubules.

Biogenesis of transverse tubules in skeletal muscle in vitro

1991 ◽  
Vol 145 (1) ◽  
pp. 77-90 ◽  
Author(s):  
Bernhard E. Flucher ◽  
Mark Terasaki ◽  
Hemin Chin ◽  
Troy J. Beeler ◽  
Mathew P. Daniels
Keyword(s):  
Skeletal Muscle ◽  
Transverse Tubules

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.

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