QUESTION 15 Pair the muscle type with the explanation of Calcium movement across

Question

QUESTION 15 Pair the muscle type with the explanation of Calcium movement across the membrane A. Skeletal muscle Cardiac Muscle Smooth muscle ca2+ comes from the sarcoplasmic reticulum and is released by Ca2+ entering cell through voltage gated Ca channels in the membrane which trigger the Ca-induced Ca2+ release from the sarcoplasmic reticulum 2+ B. Voltage gated calcium channels open in T-tubules and Ca2is released through the mechanical link between channels from the sarcoplasmic reticulum in the cell ca2+ must enter the cytoplasm from hormone stimulation to trigger contraction or extracellular Ca2+ must trigger the Ca-induced Ca2+ release from the sarcoplasmic reticulum.

Explanation / Answer

THE ANSWER SHOULD BE AS FOLLOWS

Skeletal muscle-(B). T tubules are present in both skeletal muscle and cardiac muscle , but predominantly in the skeletal muscle.

Cardiac muscle(A)-  The major source of calcium for the systolic calcium transient is the SR(Sarcoplasmic Reticulum). Calcium release from the SR occurs through a specialized release channel known as the ryanodine receptor (RyR); in cardiac muscle, the RyR2 isoform. Release occurs by the process of Calcium-Induced Calcium Release (CICR). The probability that the RyR is open (po) is increased by an increase of [Ca2+]i. Therefore, the calcium influx on the L-type calcium channel leads to the opening of the RyR and release of a larger amount of calcium from the SR

Smooth muscle(C)-Unlike skeletal muscle, which requires depolarization of the cell membrane and t-tubules, smooth muscle uses second messenger systems to open the calcium channels on the S.R. Receptors on the smooth muscle membrane for such ligands as endothelin (released as a paracrine agent), Epinephrine (released as a hormone or a neurotransmitter), and Ach (released as a neurotransmitter) connect to the Gq protein and lead to the production of inosital triphosphate (IP3).   The IP3 is then directly responsible for opening the calcium channels on the S.R. membrane, allowing the calcium to enter the cytoplasm of the cell.  

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