Final answer:
Ligand-gated channels open when a ligand such as a neurotransmitter binds to them, allowing ions to move across the cell membrane and alter the membrane potential, which is critical for initiating action potentials in nerve and muscle cells.
Step-by-step explanation:
When ligand-gated channels open, ions indeed move in or out of the cell, affecting the membrane potential. This occurs because a signaling molecule, or ligand, such as a neurotransmitter, binds to a specific site on the channel protein located on the cell membrane. Upon binding, the channel changes its conformation, creating an open pore through which ions can flow. The movement of ions like Na+ (sodium) into the cell or K+ (potassium) out of the cell can either depolarize or hyperpolarize the cell's membrane.
For instance, the influx of Na+ ions can cause the membrane potential to become less negative, potentially leading to depolarization. This is a pivotal step in the transmission of electrical impulses in nerve and muscle cells. The voltage across the membrane determines whether the cell is at resting potential, depolarized (less negative), or hyperpolarized (more negative). Changes in membrane potential are crucial for action potentials, which are signals that propagate along neurons and can trigger physiological responses such as muscle contraction or further neuronal signaling.
The patch-clamp technique has been instrumental in studying these processes by allowing the detection of specific ion flow and the corresponding changes in the membrane potential, thus contributing to our understanding of cell excitability and neurotransmission.