All of the following electrical changes of neurons are graded events except:

Options

A. EPSPs
B. IPSPS
C. action potentials
D. depolarizations caused by stimuli

Explanation

To solve the question "All of the following electrical changes of neurons are graded events except:", we will analyze the options provided and understand the concept of graded events in the context of neuronal electrical changes.

### Step-by-Step Solution:

1. **Understand Graded Events**: Graded events refer to changes in the membrane potential of a neuron that are proportional to the strength of the stimulus. This means that the changes can vary in magnitude and are not all-or-nothing responses.

2. **Identify the Options**: The question implies there are four options, two of which are EPSP (Excitatory Post-Synaptic Potential) and IPSP (Inhibitory Post-Synaptic Potential). We need to evaluate these options to determine which one is not a graded event.

3. **Analyze EPSP**: EPSP is a graded potential that results from the influx of positive ions (like Na+) into the postsynaptic neuron. This causes depolarization, making the neuron more likely to fire an action potential. Therefore, EPSP is a graded event.

4. **Analyze IPSP**: IPSP is another graded potential that occurs when negative ions (like Cl-) enter the postsynaptic neuron or when positive ions (like K+) leave the neuron. This causes hyperpolarization, making it less likely for the neuron to fire. Thus, IPSP is also a graded event.

5. **Consider Other Electrical Changes**: The question suggests that there are other electrical changes in neurons. Typically, action potentials are not graded events; they are all-or-nothing responses. However, since we are not given the other options, we focus on the provided ones.

6. **Conclusion**: Since both EPSP and IPSP are graded events, we must conclude that the question is likely asking for an option that is not mentioned in the transcript. However, based on the information provided, we can infer that the correct answer to the question is that action potentials are not graded events.

### Final Answer:
The correct answer is that action potentials are not graded events.

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