in the heart, calcium initiates the contraction of the hear muscles via what channel
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Calcium ions are crucial for initiating the contraction of cardiac muscle cells. Show more…
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The_______ are calcium channels in cardiac contractile cells. Opening them causes______
Madhur L.
Modification of Heart Rate: The action potential is also passed from autorhythmic cells to the contractile cells, first in the atria (they contract first) and then in the ventricles (they contract second). The autorhythmic cells of the heart set the intrinsic heart rate. While the heart does not require external stimulation to beat, it can be modified by hormones and neurotransmitters. The autonomic nervous system can increase or decrease heart rate; the (i) sympathetic nervous system, via norepinephrine and epinephrine, increases whereas the (j) parasympathetic nervous system, via acetylcholine, decreases heart rate. Going from Autorhythmic to Contractile Cells: The action potential of contractile cells results in depolarization of the sarcolemma, which spreads down the t-tubules of an individual cell and spreads among cells via the (k) gap junctions. Within a contractile cell, the action potential results in an influx of (l) Calcium ions into the intracellular fluid/sarcoplasm via the opening of the (m) L-type Ca2+ channel. Once in the cell, the calcium from the extracellular fluid aids in the release of (n) calcium from the (o) SR. This creates a calcium spark. Several calcium sparks result in a calcium (p) signal. The Ca2+ ions bind to (q) troponin resulting in a conformational change. This conformational change moves (r) thus exposing the actin binding sites on (s) tropomyosin, the motor protein behind contraction. These intracellular mechanisms are responsible for the mechanical contraction of the heart. In order for relaxation of contractile cells to occur, calcium ions need to be moved across the contractile cell membrane via the (t) or sequestered back into the (u) via the calcium ATPase. Thus, (v) ions and (w) are required for contraction and relaxation of the heart.
Adi S.
In the SA (sinoatrial) node, there are three types of channels: Voltage gated sodium, potassium, and ______________ channels, which allow the influx of calcium.
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