<p>I need to know which of the following statements are correct, if any:</p>
<p>1)</p>
<pre><code>[pre]------&gt;[post]
</code></pre>
<p>Single postsynaptic neuron: when [pre] fires, [post] fires, too (a single spike is enough to make the postsynaptic neuron's potential cross its threshold). This allows signals to be transmitted, e.g., along nerve fibers.</p>
<p>2)</p>
<pre><code>[pre]------&gt;[post1]
       \---&gt;[post2]
</code></pre>
<p>Two postsynaptic neurons: when [pre] fires, [post1/2] do not necessarily fire (depends on their current membrane potential).
The spike splits when it finds a branching in its path, and the two resulting spikes have half the amplitude of the original one. When they cross a node of Ranvier, in case there is one, their amplitude is reset to a normal value.</p>
<p>The meaning of points 1) and 2) is that a presynaptic neuron has a strong effect if connected to a few postsynaptic neurons, and a weak effect if connected to many (conservation of energy).</p>
<p>3)</p>
<p>Effect on postsynaptic neuron of a presynaptic neuron firing in the following configurations:</p>
<ul>
<li>Excitatory presynaptic neuron and excitatory synapse: increase potential and eventual firing.</li>
<li>Excitatory presynaptic neuron and inhibitory synapse: decrease potential.</li>
<li>Inhibitory presynaptic neuron and excitatory synapse: decrease potential.</li>
<li>Inhibitory presynaptic neuron and inhibitory synapse: increase potential and eventual firing.</li>
</ul>
<p>Which formulae apply to the case of inhibitory neurons/synapses, both in relation to the change in membrane potential and synaptic weight? Is it enough to use the formulae for the excitatory case with a negative value for the potential and the weight?</p>

CC BY-SA 4.0
2024-02-16T17:48:19.480Z
1) almost never happens in biology, 2) never does and conservation of energy has nothing at all to do with it, 3) makes absolutely no sense and none of these relate to your final questions. I suggest you start over by reading a neuroscience textbook rather than guessing what it might say. To ask a good question here, try to build your question on what you've read: cite sources for things that you do know are true. Chain those ideas together.
Bryan Krause
CC BY-SA 4.0
2024-02-16T18:02:46.940Z
@BryanKrause - I asked those question because I found no answers reading around. Feel free to expand your answer, or give me some references. Thank you.
Pietro
CC BY-SA 4.0
2024-02-16T18:04:13.863Z
I'd recommend a neuroscience textbook like Purves Neuroscience or Kandel Principles of Neural Science. Where have you read around?
Bryan Krause
CC BY-SA 4.0
2024-02-16T18:35:21.933Z
I looked at Kandel's, and online, but could not find the details I am looking for.
Pietro
CC BY-SA 4.0
2024-02-16T18:37:00.257Z
You don't need the details yet, you need to understand the bigger picture.
Bryan Krause
<neurophysiology>
Effect of number of post-synaptic neurons, and of inhibitory neuron/synapse, on post-synaptic neuron potential
Pietro
# Effect of number of post-synaptic neurons, and of inhibitory neuron/synapse, on post-synaptic neuron potential

(Asked by: username_0 on 2024-02-16)

I need to know which of the following statements are correct, if any:
1)
[pre]------>[post]

Single postsynaptic neuron: when [pre] fires, [post] fires, too (a single spike is enough to make the postsynaptic neuron's potential cross its threshold). This allows signals to be transmitted, e.g., along nerve fibers.
2)
[pre]------>[post1]
       \--->[post2]

Two postsynaptic neurons: when [pre] fires, [post1/2] do not necessarily fire (depends on their current membrane potential).
The spike splits when it finds a branching in its path, and the two resulting spikes have half the amplitude of the original one. When they cross a node of Ranvier, in case there is one, their amplitude is reset to a normal value.
The meaning of points 1) and 2) is that a presynaptic neuron has a strong effect if connected to a few postsynaptic neurons, and a weak effect if connected to many (conservation of energy).
3)
Effect on postsynaptic neuron of a presynaptic neuron firing in the following configurations:

Excitatory presynaptic neuron and excitatory synapse: increase potential and eventual firing.
Excitatory presynaptic neuron and inhibitory synapse: decrease potential.
Inhibitory presynaptic neuron and excitatory synapse: decrease potential.
Inhibitory presynaptic neuron and inhibitory synapse: increase potential and eventual firing.

Which formulae apply to the case of inhibitory neurons/synapses, both in relation to the change in membrane potential and synaptic weight? Is it enough to use the formulae for the excitatory case with a negative value for the potential and the weight?

**Tags:** neurophysiology

> **Comments:**
> **username_1**: 1) almost never happens in biology, 2) never does and conservation of energy has nothing at all to do with it, 3) makes absolutely no sense and none of these relate to your final questions. I suggest you start over by reading a neuroscience textbook rather than guessing what it might say. To ask a good question here, try to build your question on what you've read: cite sources for things that you do know are true. Chain those ideas together.  
> **username_0**: @BryanKrause - I asked those question because I found no answers reading around. Feel free to expand your answer, or give me some references. Thank you.  
> **username_1**: I'd recommend a neuroscience textbook like Purves Neuroscience or Kandel Principles of Neural Science. Where have you read around?  
> **username_0**: I looked at Kandel's, and online, but could not find the details I am looking for.  
> **username_1**: You don't need the details yet, you need to understand the bigger picture.  

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## 0 answers

