Im 90% sure the answer is b) chemoreceptors
Not sure if I'm correct but my best guess is the cell membrane seeing as it surrounds the cell itself and is responsible for allowing certain molecules to diffuse in or out of the cell. Good Luck! :)
Reproduction of a cell from an existing cell
Answer:
1. ridges and trenches (either answer is acceptable)
2. mid-atlanitc
3. subduction zone
4. molten
5. oceanic trenches
Explain:
6. Rocks in the ocean eventually get subducted back into earths mantle due to slab pull. New rocks form at mid-ocean ridges as ridge forces two plates to diverge.
It permits calcium to leave the sarcoplasmic reticulum and enter the cytosol. During muscle contraction, the binding of acetylcholine initiates an excitatory impulse, which is transmitted to the deep of the muscle via T tubules. T tubules are the invaginations of cell membranes of muscle cells (sarcolemma). When the action potential travel down the t-tubules, they change shape and allow the calcium ions to enter into the sarcoplasm from the sarcoplasmic reticulum.