Depolarizing local potentials are caused by an influx of.
The Correct Answer and Explanation is :
Answer:
Depolarizing local potentials are caused by an influx of sodium ions (Na⁺).
Explanation:
Depolarizing local potentials occur when a cell’s membrane potential becomes less negative (closer to zero) due to ion movement. Normally, a neuron’s resting membrane potential is around -70 mV, maintained by the sodium-potassium pump and selective permeability to ions like potassium (K⁺).
When a depolarizing stimulus, such as a neurotransmitter, binds to receptors on a neuron’s membrane, it opens ligand-gated sodium channels. This allows sodium ions (Na⁺), which are highly concentrated outside the cell, to rush into the cell due to both the concentration gradient and the electrical gradient. As positively charged sodium ions enter, the inside of the cell becomes less negative, leading to depolarization.
Depolarizing local potentials are graded, meaning their strength depends on the intensity of the stimulus. If enough sodium enters to bring the membrane potential to the threshold (usually around -55 mV), voltage-gated sodium channels open, triggering an action potential. However, if the local potential does not reach this threshold, it will dissipate, and no action potential will occur.
This process is essential for communication within the nervous system. Local potentials can occur in dendrites and cell bodies as part of signal integration. Depolarization may lead to various responses depending on the type of neuron and the summation of multiple local potentials.
Understanding depolarization is crucial for fields like nursing and healthcare because conditions such as epilepsy, neuropathies, and the effects of anesthetics often involve alterations in sodium ion movement and membrane potentials. For example, some medications work by blocking sodium channels to reduce excitability in neurons, helping to manage pain or prevent seizures.