Learning diary blog 2

The third lecture mainly focused on synaptic transmission and topics around it. It recalled old familiar things but also taught new ones. The basic principle of synapses is that there are synapses because the information cannot just jump over the gap between them two neurons.

We started with the basics of synaptic transmission and defined the main structures: Post-synaptic and pre-synaptic neuron and axon which conducts the signal aka action potential to synapse. The one new information was that the action potential is always the same: discrete and binary even it branches to thousands of target cell. One question which came to mind was that, how the action potential can be always the same, how does it retain its form and value even it is delivered to one target cell or then to 1000 cells?

This action potential is so important because it includes the information which must be delivered. When the action potential arrives to axon terminal and depolarizes the presynaptic membrane the Ca2+-channels open and the Ca2+-ions will flow inside. This concentration change causes the vesicles to release the neurotransmitters to synaptic cleft. To calculate the reversal potential there is this formula called Nerst equation which was familiar already but the new one was Goldman equation which gives the membrane potential when the concentrations and permeabilities are known: Goldman equation (reference: lecture slides)

It was new that action potential can be generated with microelectrodes. The action potentials frequency can be controlled by electrical current. If the electrical current is continuous and
just goes above threshold, it generates action potentials which frequency is one Hertz. If the current increases the frequency increases too. A new concept is the Voltage-gated sodium channel, which properties explains action potentials properties. I find the optogenetics sounds interesting. How it can be possible to generate action potential with genes and light? Can it be used to form certain emotions depending on the light.

The release of neurotransmitter from vesicles were quite understandable but secretory granules is little bit unclear. Does secretory granules store only peptides or also amino acids and amines and does it have similar structure as vesicles so the neurotransmitter release is also similar?

Posted by Roosa Wallén

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