Week 3, 4 Reading and Research Part 2 — Erin Kasiou
Scintillessentialism and the Brain
The way the brain grows and changes in response to stimuli is a perfect example of scintillessentialism, the e-concept I have created. Briefly, scintillessentialism encapsulates the importance of the tiny elements of nature — from the tiny seeds that grow into the tallest of oak trees, to the final droplets of water vapour that push a rain cloud over the edge and cause a storm. However, a key element of the definition of the word ‘scintilla’ is a 'tiny spark', which inspired me to write about the smallest sparks I can think of; the electrical potentials in the brain.
PART 1 — NEURON DEPOLARISATION
The depolarisation of neurons is what we might think of as the ‘electrical signals’ running through our brain cells, prompting everything from our thoughts to our actions. Whilst these signals aren’t quite ‘sparks,’ lighting up the inside of our skulls, the process of neurons depolarising and firing can be captured using fluorescent microscopes, as seen in the image and video above. The result is a spectacular light show. This depolarisation is a result of ions moving in and out of the cell membrane, generating an electrical potential (or action potential). This electrical potential causes chemical messengers to move from one neuron to the next, generating the conditions for depolarisation over and over again such that the signal spreads throughout the brain. (Blaustein, Kao & Matteson 2020, p. 60) Such is the importance of this tiny spark, its scintillessentialism; this is the generating instance for the functioning of the brain. It is how you can see the vibrant colours of the flowers in your garden, how you feel love for your family and friends, how you pick up a warm cup of tea and raise it to your lips. This tiny spark is everything.
PART 2 — LONG-TERM POTENTIATION
The minuscule is essential to the brain in more ways than one. It is not only important for how we think, but also how we learn, and how we remember. A process called long-term potentiation LTP strengthens the connections between synapses by increasing the number and frequency of neurotransmitter release and/or increasing the number of AMPA receptors on the postsynaptic neuron — a process which is explained in the video above. This image is of the architecture of an AMPA receptor, determined by a process called cryo-electron microscopy. It is amazing that such a tiny thing can be captured by modern science, and even more amazing that such a tiny thing can be so important to the memories we hold dear! In fact, the hurdle LTP must overcome is a single magnesium ion, blocking the channel of an NMDA receptor. (Vanderah, Gould, & Nolte 2016, p. 194) Only once this is removed can the connections necessary to LTP be formed, and thus can learning and memory function occur. This is, once again, a perfect model for the concept of scintillessentialism.
PART 3 — DENDRITIC ARBORISATION
A final example of scintillessentialism in the brain is dendritic arborisation. Dendrites are the small branch-like filaments on each end of the neuron. They are the means by which neurons send and receive chemical signals. Dendritic arborisation describes the process of these dendrites extending out towards the dendrites of other neurons, creating new synapses. It results from the repeated use of certain neurons and pathways. (Neuroscientifically Challenged, n.d) Like LTP, dendritic arborisation is important for learning and memory. It increases the complexity of the brain by allowing for more efficient pathways throughout. These processes (LTP and dendritic arborisation) are important contributors to the human brain’s superior complexity, as compared to other animals. Such tiny processes with such pivotal roles in our existence!
References
ArajoulabUB 2020, "Fireworks": Class IV multidendritic neuron from the Peripheral Nervous System of #Drosophilamelanogaster. Concretely, the ddaC #neuron, famous due to its large #dendritic arborisation field. Third instar larva image acquired through #confocal microscopy, microscope image, accessed 20 April 2021, <https://twitter.com/SEBiolDev/status/1341328862450507776/photo/2>
Blaustein, MP, Kao, JPY & Matteson, DR 2020, Cellular physiology and neurophysiology 3rd edition., Elsevier, St. Louis, Missouri.
Dendritic arborisation n.d., Neuroscientifically Challenged, accessed 20 April 2021, <https://www.neuroscientificallychallenged.com/glossary/dendritic-arborization>
Ji N 2020, Using a two-photon fluorescence microscope with an extra-large field of view, UC Berkeley researchers imaged neurons (green) in a large chunk of the cortex of the brain of a living mouse. The area shows neurites in a volume of 4.2 mm × 4.2 mm x 100 microns. The dark branches are blood vessels., microscope image, UC Berkeley, accessed 20 April 2021, <https://news.berkeley.edu/2020/03/19/high-speed-microscope-captures-fleeting-brain-signals/>
Ji N 2020, When a neuron fires, calcium flows into the cell in a wave that sweeps along the cell body. Images of this infragranular neuron were obtained three times per second by two-dimensional scanning with a Bessel focus. Redder structures are deeper in the mouse cortex., online video, accessed 20 April 2020, <https://news.berkeley.edu/2020/03/19/high-speed-microscope-captures-fleeting-brain-signals/>
Neuroscientifically Challenged 2018. 2-Minute Neuroscience: Long-Term Potentiation (LTP), online video, accessed 20 April 2020, <https://www.youtube.com/watch?v=-mHgPfXHzJE>
Vanderah, TW, Gould, DJ & Nolte, J 2016, Nolte's The human brain : an introduction to its functional anatomy Seventh edition., ELSEVIER, Philadelphia, PA.
| Zhao Y, Chen S, Yoshioka C, Baconguis I, Gouaux E 2016, Architecture of fully occupied GluA2 AMPA receptor-TARP complex elucidated by cryo-EM, microscope image, accessed 20 April 2021, <https://www.ncbi.nlm.nih.gov/Structure/pdb/5KK2> |