DID YOU KNOW? 🧠 (~60 seconds)
Briefly, synaptic plasticity is the ability of the brain’s structure to change and adapt. For many years, humans believed that traits like intelligence and grit were inherited qualities that are predetermined and cannot be improved. However, the discoveries of synaptic plasticity reveals that this is certainly not true; the synapses corresponding to that trait can strengthen or weaken over time in response to use or disuse, and this can lead to structural changes of the brain. This article will inform the role of glutamate, a major excitatory transmitter of the mammalian brain that plays an essential role in learning, aging, and synaptic plasticity.
DIVE DEEPER 🔎 (~4 minutes)
The glutamate activates 2 very important receptors: NMDA & AMPA receptors. Both allow positively charged sodium ions (Na+) to flow into the cell, which can make the cell more positive (we call this “depolarization”). Unlike the AMPA receptor, however, the NMDA pathway is normally blocked by magnesium (Mg), so even if the glutamate binds to the NMDA, nothing happens. The magnesium in the NMDA can be removed by the *depolarization of the cell. And this ‘depolarization of the cell’ is triggered by the Na+ ions flowing through the AMPA receptors that have no blockage. Then, Mg is removed from the NMDA pathway through depolarization. What now? NMDA is permeable to calcium. That is, thanks to the opening of the NMDA receptor, calcium ions will flow into the cell and trigger second messenger pathways that makes even more AMPA receptors.
What does this mean? Think of this in terms of a flow chart:
More AMPA receptors on one neuron → More Na+ into the cell → More depolarization → More removal of Mg blockage on NMDA → More Ca2+ into the cell → Ca2+ helps create more AMPA receptor proteins → More AMPA receptors on one neuron → (start from beginning and repeat)
→ This ultimately means that the cell is MORE excitable and MORE likely to fire an action potential and process information!
This is the fundamental science behind synaptic plasticity. I will write more about this in the future, so stay tuned for more short and accessible neuroscience information!
Fun fact: Do you ever happen to just blank out? It could be due to the fact that certain cells in your body have very little AMPA receptors to depolarize and remove the Mg blockage from the NMDA receptor. And the glutamate binding to the NMDA receptor won’t do anything at all since it is blocked by Mg! It definitely won’t help you think.
*Depolarization means that the cell becomes more positive due to the influx of positively charged ions in the neuron cell. Remember, the ions in our bodies are charged particles, thus the neuron can be mapped as an electrical circuit (physics, anyone?). In this case, the influx of positively charged sodium ions depolarized the cell/made the cell more positive.
Photos:
https://www.verywellmind.com/what-is-brain-plasticity-2794886
https://www.news-medical.net/life-sciences/What-are-NMDA-Receptors.aspx
