Which structure in cardiomyocyte sarcolemma (heart muscle cell) allows an action potential to pass from one to another?

Question

BlackTom AI · Accepted Answer

To understand how an action potential passes from one cardiomyocyte to another, we need to recall the functional roles of different sarcolemmal structures in heart muscle.
Option 1: T-tubules. These invaginations of the sarcolemma help propagate the action potential into the cell's interior, promoting excitation-contraction coupling within a single cardiomyocyte. However, they are not primarily responsible for cell-to-cell electrical spread between neighboring cells.
Option 2: GAP junctions. These specialized intercellular channels at the intercalated discs physically connect adjacent cardiomyocytes and permit direct ionic current flow, enabling the action potential to pass from one cell to the next. This is the key structure for electrical coupling across cells in heart tissue.
Option 3: Desmosomes. Desmosomes provide strong mechanical adhesion between cells, helping them resist separation during contraction. They do not conduct ions or propagate electrical signals, so they do not mediate action potential transmission.
Option 4: Sarcoplasmic reticulum. This organelle stores and releases calcium to trigger contraction within an individual cell, but it does not form pathways for current between cells, so it does not facilitate intercellular passage of the action potential.
In sum, the structure that enables the electrical connection allowing an action potential to pass from one cardiomyocyte to another is the gap junction. The other options correctly describe important components of excitation-contraction coupling within a single cell or mechanical adhesion, but they do not support intercellular electrical propagation.

Which structure in cardiomyocyte sarcolemma (heart muscle cell) allows an action potential to pass from one to another?单项选择题

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