An interesting way to view the human experience is that we are a mind that is controlling a spaceship made of meat, bones and bits. The mind is the sense of self which is a combination of the quickly changing software that runs on the biological hardware our brains. All mental health is in our head – and that is because that is where our brain is. Medically, we refer to different aspects of our brain as neurology.
Most of our brain is in the skull, a protective layer of bone. Beneath the skull is the meninges, 3 layers (dura mater, arachnoid mater, and pia mater) of web like structure filled with fluid that cushions the brain so that our brain s suspended safetly within our skull. This is like the seatbelt in a car that helps your soft and breakable body not fly around the inside of your hard car when you turn corners, speed up, slow down or suddenly stop. The meninges has some other interesting activities around the health of your brain to do with nuritent delivery, flushing toxins and filtering. This circulatory system is a fairly new field of study. For more, look up the Subarachnoidal Lymphatic-Like Membrane [Link] for more about this.
Neuronal Cells
Your brain is filled with various different kinds of cells. Some are tiny, some are huge.
Types of Cells
- Neurons, aka nerve cells, are made up of:
- Interneurons,
- Pyramidal cells including Betz cells,
- Motor neurons (upper and lower motor neurons), and
- Cerebellar Purkinje
- Glial cells, the Neuronal Macroglia is the collective term for the four sub-types:
- Astrocytes,
- Oligodendrocytes, and
- Ependymal cells
- Microglia
- Neural stem cells, and
- Blood vessels
Study of our brains has mostly focused on how neurons interact with each other. Glial cells are a relatively new area of study as it has recently been demonstrated that Glial cells do more than just maintain neurons. Neural stem cells differentiate and become either neurons or glia. Blood vessels are one of two cirulatory systems for the brain, and carry the usual blood contents to the brain and waste metabolic products from the brain.
You may have noticed “most of our brain is in our skull”, which begs the question, what part of the brain isn’t? The nose has olfactory sensory neurons that samples the air you inhale through your nose and reports your sense of smell. The olfactory sensory neurons are directly connected to your brain, growing through a part of your skull called the cribifrom plate of the ethmoid bone, connecting straight to your cerebellum. Another part of your brain protrudes from your optic foramen, via the optic nerve which is the axoms of neurons. The retina is a mini-processing centre converting light into action potentials to be sent along the optic nerve.
Lastly we have the spinal collum and the entire body nerve system. The central nervous system is your brain and spine. The neuron in your skull that triggers a muscle to twitch or relax has an axon that travels out of the skull and down the spine and then out to the muscle they trigger. The peripheral nervous system has interconnecting neurons cells that pass on sensory data, such as hot, cold, sharp, blunt and itch.
Neurons
Neurons are polarised cells that are sepecialised for passing messages via a chemical process called “action potential”, which are conducted from the centre of the neuron down a long branch called an Axon towards another neuron cell. The sender Neuron will use a chemical cascade down the Axon involving calcium and potasium, sending an electrical signal via ions. This signal gets to the end of the Axon, building a charge until it squeezes from reservoirs at the end of the Axon a fluid called a Neurotransmitter. The Neurotransmitter goes from the reservoir into the Synaptic Gap of the Synapse, bridging the Axon and the Dendrite (the receiving branch of the Receiving Neuron). The Neurotransmitter allows the ion charge to go from the end of the Axon to the beginning of the Dendrite, which then continues the signal to the other Neuron.
If the Neurotransmitter level is absent or low, the Axon has to build up much more charge to get a signal across the Synaptic Gap, it may even fail to bridge the gap entirely. If the Neurotransmitter level is too high, the charge crosses prematurely. It is important that the right level of Neurotransmitter is present.
We have a number of different Neurotransmitters that specialise in different profiles and are used to get different effects from the gap and Neuron signal. More on those later.
After the signal has fired, some of the excess Neurotransmitter is re-absorbed into the Axon Neurotransmitter Reservoir. This is what “Uptake” is referring to. The uptake is mediated by a Neurotransmitter dependent Transport chemical. Flooding this chemical with a dummy other chemical inhibits the ability for the Transport molecule to take the associated Neurotransmitter back to the Reservoir. This is “Uptake Inhibition”. That leaves some of the Neurotransmitter in the Synaptic Gap, decreasing how much of the Neurotransmitter is needed to make the Neuron signal cross the Synaptic Gap, and decreasing how much replacement Neurotransmitter must be synthesised by the Axon to top the Reservoir up.
Excess Neurotransmitter is flushed away, often becoming another Neurotransmitter that has
Glial Cells
It was assumed for many decades that glial cells merely maintained the neurons We are now aware that glial cells also play a role in neurotransmission, synaptic connections and autonomous actions such as breathing.
Scientific learning on this has been rapid and this is new section of study.
Neurotransmitters and Synapses
We have a detailed section about how Neurotransmitters work [LINK].
Briefly, Neurotransmitters are chemicals that our brain uses to turn signal pathways on and off, much like electronic circuits in a computer. Rather, we based computers off the way that we thought our brains worked. Neurotransmitters are often hormones or other chemicals that are used for very different functions outside of our brain in the general body.
Most of the important neurotansmitters are made both in our body for body use, and separately in our brain for use as neurostransmitters. This is because most of our neurotransmitter chemicals cannot pass through the protective Blood Brain Barrier. This means that taking a medication that contains the neurotransmitter generally doesn’t affect our brains, only the rest of the body. As such, the medications we take to help our brains often helps our brain make more of the neurotransmitter, make less, or affect how the neurotransmitter sends signals.
Medial Prefrontal Cortex and the Executive Function
The medial prefrontal cortex (mPFC) is a crucial cortical region. It is one of the primary things that separates our human thinking from other animals, even other primates. The mPFC is poorly developed in children, only starting to mature from the onset of puberty, completing the full growth in our mid 20s. Effectively, the mPFC houses the interconnecting networks of neurons referred to as the Executive Function.
What the Executive Function Does:
- Cognitive process (understanding, reasoning, logical, assessment)
- Regulation of emotion (not too high, not too low)
- Motivation (planning and execution of behavior)
- Sociability (interacting with others)
- Working memory (holding relevant timely information that speeds up tasks)
- Inhibitory response control (holding back doing the wanted action)
- Maintenance of focused attention and concentration
The vast majority of medical conditions and neurodivergences that are haphazzadly lumped under “mental illness” is effectively a dysfunction of the mPFC, which is often connected to Dopamine. [External LINK]
Research shows us that perceived external stressors affect how the Mesolimbic Dopamine Pathway operates. These can be physical stressors or psychological stressors. This then affects how the Mesocortical Dopamine Pathway affects our behavioural expression.
