an inhibitory local potential causes which of the following

Charlotte

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28-02-2025

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An Inhibitory Local Potential Causes Which of the Following? Understanding Hyperpolarization

An inhibitory local potential, also known as an inhibitory postsynaptic potential (IPSP), causes hyperpolarization of the neuronal membrane. This means the membrane potential becomes more negative than the resting potential. Let's delve deeper into what this means and the consequences of this hyperpolarization.

Understanding Neuronal Membrane Potential and Local Potentials

Neurons communicate through electrical signals. The resting membrane potential, typically around -70 mV, is maintained by the unequal distribution of ions across the neuronal membrane. This delicate balance is crucial for the neuron's ability to transmit signals. Local potentials are temporary changes in this membrane potential. They are graded, meaning their magnitude varies depending on the strength of the stimulus. Unlike action potentials, local potentials are not all-or-nothing; they can be small or large.

Inhibitory Local Potentials (IPSPs) and Hyperpolarization

Inhibitory local potentials are caused by the opening of specific ion channels in the postsynaptic membrane. These channels often allow either potassium ions (K+) to flow out of the neuron or chloride ions (Cl-) to flow into the neuron. Both actions result in the same outcome:

• Potassium efflux: The outward movement of positively charged potassium ions makes the inside of the neuron more negative.
• Chloride influx: The inward movement of negatively charged chloride ions also makes the inside of the neuron more negative.

This increase in negativity is precisely what we define as hyperpolarization. It moves the membrane potential further away from the threshold required to trigger an action potential.

What are the consequences of hyperpolarization?

Hyperpolarization caused by an inhibitory local potential has a crucial role in neuronal signaling:

• Reduced Excitability: The neuron becomes less likely to fire an action potential. The membrane potential is now further from the threshold, requiring a stronger excitatory stimulus to reach that threshold. This is the primary effect of an IPSP – to inhibit the neuron's activity.
• Summation: IPSPs, like excitatory postsynaptic potentials (EPSPs), can undergo summation. Multiple IPSPs occurring close together in time or space can add up to produce a larger hyperpolarization, further inhibiting the neuron. This summation can be temporal (multiple IPSPs in rapid succession) or spatial (multiple IPSPs arriving at different synapses).
• Integration of Signals: The neuron constantly receives both excitatory and inhibitory signals. The summation of these EPSPs and IPSPs determines whether the neuron will fire an action potential. IPSPs play a vital role in fine-tuning the neuron's response to incoming signals, preventing over-excitation.

In Summary: An Inhibitory Local Potential Causes...

To answer the initial question directly: An inhibitory local potential causes hyperpolarization, leading to reduced neuronal excitability. This is a fundamental mechanism in the nervous system for regulating and controlling neuronal activity. The ability to both excite and inhibit neurons allows for complex information processing and precise control of bodily functions.