Neurology

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

was assumed for many decades that glial cells merely maintained the neurons, while we are now aware that glial cells also play a role in neurotransmission, synaptic connections and autonomous actions such as breathing.

have been a rapid and new section of study.

Neurotransmitters

Dopaminergic Neurons / System

  • Protein (eaten in food)
  • Tyrosine is made from protein via digestion, which is then converted to L-Dopa (Levodopa)
  • L-Dopa passes the Blood Brain Barrier (the Dopamine made in your adrenal gland can’t, which is why you don’t treat ADHD by ingesting or injecting Dopamine)
  • Dopamine is made by recombining L-Dopa from your blood in the brain (first link in Dopaminergic chain)
    • Empower the Executive Function
      • Concentration
      • Holds short term ideas / data (like mental math rather than writing it down)
      • Problem solving, creative solutions, finding more complex viable answers than the Emergency Centre
      • Big picture task prioritisation
      • Comprehension and connecting ideas, integral to learning concepts
    • Being alert, present and higher levels of thinking
    • Manages Muscle Movement
    • Reinforces activities that improve ancient human survival, aka The Reward System
      • Enjoying food
      • Aquiring goods (browsing shops and or buying goods)
      • Learning
      • Positive Social
      • Creating

There are five types of dopamine receptors, which include D1, D2, D3, D4, and D5. Each receptor has a different function and is found in different locations.

The function of each dopamine receptor[4]:

  • D1: memory, attention, impulse control, regulation of renal function, locomotion
  • D2: locomotion, attention, sleep, memory, learning
  • D3: cognition, impulse control, attention, sleep
  • D4: cognition, memory, fear, impulse control, attention, sleep
  • D5: decision making, cognition, attention, renin secretion

The five different dopamine receptors can subdivide into two categories. D1 and D5 receptors group together (Dop Alpha for here), and D2, D3, and D4 are together in a separate subgrouping (Dop Beta). 

{D1 to D5 receptors, source: Biochemistry, Dopamine Receptors [Link]}

  • Norepinephrine is made from unused Norepinephrine
    • Situational Assessment via Sensory interpretation and Focus
      • Hyperfocus vs distractability vs impulsiveness
    • Feelings / Mood / Emotions
      • Freeze / Flight / Fight / Fawn reflex when an emergency is detected
    • Connects “want” and “plans” to “physical actions”
    • Manage pain perception, ties in with Endorphins (we think)
  • Epinephrine (aka Adrenaline) is made from unused Norepinephrine
    • At high levels, disengages the higher thinking centre and engages primal survival actions, supresses pain perception
    • At moderate levels, appears to be connected to long term memory storage

  • Serotonin is made from the amino acid component of protein called tryptophan
    • Powers the neurotransmitter homeostatic system (prompting direct creation/deletion of neurotransmitters to get to he Goldilocks Zone where able) – this is currently conjecture and we need more studies to confirm this
    • First link to decrease alertness/agitation (soporiphic/sleep, parasympathetic trigger)
  • Melatonin is made from unused Serotonin, and also from your bodies adrenal gland as this last link in the Dopaminergic chain can pass through the Blood Brain Barrier
    • High levels, prompts the brain to consider sleeping now if the adrenal level is low
      • Being in darkness / dim light prompts the body to produce Melatonin
    • Low levels, prompts the brain to be awake
      • Bright light / daylight (especially sky blue) prompts the body to delete Melatonin

{Biochemistry, Seotonin [Link]}

Synapse

The meeting of Neurons

{Synaptic Transmission [Link]}

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