The Brain - Part 2
Neurons, neurotransmitters and drugs (Yes, watches are a drug!)
The previous post on this subject covered the astonishing hypothesis, materialism and dualism and we got down to the arguments for and against materialism, culminating in a ‘conclusion’ of sorts, which was that materialism, however uncomfortable, is a view that the science steers us to adopt. This time, it might feel like a bit of a technical tangent, talking about neurons… and how we contrast our brains with ‘computing systems’ - certainly not for everyone, but if you enjoy websites like HowStuffWorks or YouTube channels like SmarterEveryDay … then you will probably enjoy this too!
What is the physical ‘seed’ of thought? What is the source of our emotions, or decision-making, our passions, or pains, and everything else? Well, according to scientific consensus, all these things are a product of brain activities. The brain is literally one of the most complex structures in the known universe, and yet all we see when we take it out of the head is a heap of tightly packed grey meat! It's called grey matter but only when it isn’t in a head. When inside a head, it is pulsing with blood, and therefore bright red. Either way, you can’t help but feel a little sympathetic when you hear an argument that suggests this lump of meat is responsible for free will, love and consciousness!
Well, let’s make the argument… starting with neurons. Basically, neurons are nerve cells which send messages all over your body, loosely referred to as ‘the building blocks of thought’… the most basic unit in a brain. It's no surprise, therefore, that they call the study of the biological basis of thought “neuroscience” - obviously, it all starts with the neurons! When neurons transmit signals through the body, part of the transmission process involves an electrical impulse called an action potential.
What other parts are there?
Here's a diagram that depicts a typical neuron. The process of normal neuronal firing takes place as a communication between neurons through electrical impulses and neurotransmitters. When a neuron is not sending signals, the inside of the neuron has a negative charge relative to the positive charge outside the cell. Electrically charged atoms (ions), maintain the positive and negative charge balance.
To better understand this process, it is important to understand the parts of a neuron, including the soma, dendrites and axons. Basically, dendrites receive signals from other neurons, and these signals are either excitatory or inhibitory (positive and negative) and we will come back to this point later. The soma, in turn, can be thought of as the “brain” of the brain cell, as it processes the input/information from the dendrites into the cell and determines if it is important enough to pass along to another cell.
The axon hillock is located near the end of the soma and controls the firing of the neuron. If the total strength of the signal exceeds the threshold limit of the axon hillock, the structure will fire a signal (known as an action potential) down the axon.
So the axons obviously pass information from neuron to neuron, similar to electrical wires in a house. Axons are much longer than dendrites. In fact, there are axons