Chemical Messengers

[Marcy_Sara]

Hello,

I am going to be as clear as possible in my question, but i'm really confused . I was wondering, in the Chemical messengers' chapter, what is the difference between epsp and ipsp, knowing that one is created by positively charged ions and the other by negatively charged ions. Will it change something in the action potential if it's negative or positive? Will the ions' charge affect the synaptic transmission ?

[Brain Bee]

You seem to understand more than you think

The difference is explicit in the name. EPSP: Excitatory postsynaptic potential. IPSP: Inhibitory postsynaptic potential. You are absolutely correct when you say that an EPSP is when POSITIVE ions flow INSIDE the neurons, and that an IPSP is when NEGATIVE ions flow INSIDE the neurons.

When positive charges flow inside neurons, the resting membrane potential gets more positive, and thus closer to the threshold for the generation of an action potential. This is why it is called EXCITATORY, because it can trigger action potentials.

When negative charges flow inside neurons, the resting membrane potential gets more negative, which sends the resting membrane potential further from the threshold of action potential. This is why it is called INHIBITORY, because it decreases the chance to trigger action potentials.

Remember: Action potentials are ALL OR NOTHING events that occur when the resting membrane potential reaches the threshold. Under normal physiological circumstances, they are always positive (membrane potential going up to more positive values, then down again) and always the same overall size and shape. Synaptic transmission only determines whether action potentials will occur and, if so, how many and at what frequency.

I hope this clarifies things! If not, feel free to ask further questions

[Thank you]

Thank You that was really helpful