Biology, 29.10.2019 01:31, lizdominguez101

What causes the release of calcium ions into the sarcoplasm from the terminal cisterns?

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answered: vuqepete4528

Excitation-contraction coupling

Explanation:

The T-tubules are located between the terminal cistern adjacent to the RS, forming a triad consisting of two terminal cisterns and the T-tubule. The RS-tubule-T junctions and their associations with myofibrils develop in a series of consecutive steps, where the formation of junctions between the two membrane systems is done concurrently, initiating molecular changes in both membrane systems.

When the potential for nervous action reaches the muscular membrane, it undergoes depolarization that is transmitted to the depths of the cell by the membranes of the tubular-T system. When the action potential of the tubules is detected by a dihydropyridine receptor located at the junction of the tubule with the sarcoplasmic reticulum cistern, a mechanism not yet elucidated produces the opening of the receptors to ryanodine, which function as channels for the calcium. When these channels open, as the concentration of calcium ions within the RS is much higher than in the cell's cytosol, these ions leave their deposit to begin the process of interaction between thick and thin filaments, muscle contraction.

This series of events is called the 'excitation-contraction coupling' (e-c) and several proteins specifically located in the RS-tubule-T junction have essential roles in them. The dihydropyridine receptor (DHPR) in the T-tubule detects the voltage across the membrane and its activation causes the release of Ca2 + from the RS, while the RyR / Ca2 + release channel is located in the junction RS and is responsible for the release of Ca2 + from its storage locations. Both RyR and DHPR are necessary for proper muscle development, although none of them are necessary for T-RS anchoring or the search and / or association of CLQ and tradin in the binding RS.

answered: Guest

Mantle convection is the slow creepingmotion of earth's solid silicate mantle caused by convection currents carrying heat from the interior to the planet's surface.[1][2] the earth's surface lithosphere, which rides atop the asthenosphere (the two components of the upper mantle), is divided into a number of plates that are continuously being created and consumed at their opposite plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with seafloor spreading. this hot added material cools down by conduction and convection of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of subduction usually at an ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4] while in other regions, this material is impeded from sinking further, possibly due to a phase transition from spinel to silicate perovskiteand magnesiowustite, an endothermic reaction.[5]the subducted oceanic crust triggers volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6] and mantle plumes.[7]it is because the mantle can convect that the tectonic plates are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the hadean period, resulting in gravitational sorting of heavier molten iron, and nickel elements and sulphides in the core, and lighter silicate minerals in the mantle.

answered: Guest

Digestion because it removes waste