Nerve Cells
• So the brain is boss, but it can't do it alone. It
needs some nerves — actually a lot of them. And
it needs the spinal cord, which is a long bundle of
nerves inside your spinal column, the vertebrae
that protect it. It's the spinal cord and nerves —
known as the nervous system — that let
messages flow back and forth between the brain
and body.
– Your brain is made up of 100 billion nerve cells.
– Different types of cells carry out a range of
different functions.
– Each cell is connected to around 10,000 others.
– So the total number of connections in your brain is
about 1000 trillion.
– There are Neurons (10%) and Glial Cells (90%) –
these combined are your “brain cells.”
Glial Cells
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Glial cells are nerve cells that don’t carry nerve impulses.
They are known as the "glue" of the nervous system.
They make up 90 percent of the brain's cells and provide support and protection
for neurons.
• They have been listening in on the conversations among neurons all along. They
also interact chemically with neurons.
• Glia can interrupt and redirect neuron messages and signals.
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The four main functions of glial cells are
1. to surround neurons and hold them in place,
2. to supply nutrients and oxygen to neurons,
3. to insulate one neuron from another, and
4. to destroy pathogens and remove dead neurons.
• An important type of Glial Cell is called an Astrocyte
Neurons
• Neurons send and receive electro-chemical signals to and from the brain
and nervous system at up to 200mph.
• Each neuron has tiny branches coming off it that let it connect to many
other neurons.
• There are about 100 billion neurons in the brain.
• There are many types of neurons. They vary in size from 4 microns (.004
mm) to 100 microns (.1 mm) in diameter. Their length varies from a
fraction of an inch to several feet.
• The neurons of the brain require a lot of energy.
• Even though the brain makes up only 2% of our body weight, it:
– Receives 15% of the cardiac output,
– Consumes 20% of total body oxygen, and
– Uses up 25% of total body glucose.
• The energy consumption for the brain to simply survive is 0.1 calories
per minute, but can be as high as 1.5 calories per minute during
crossword puzzle-solving!!
NEURONS
Neural Connections
• When you were born, your brain came with all the neurons it will ever
have, but many of them were not connected to each other.
• When you learn things, the messages travel from one neuron to another,
over and over.
– A typical neuron has about a thousand to 10 thousand synapses
(points of connection between two nerve cells) which means that it
communicates with a thousand to 10 thousand other neurons,
muscle cells, glands, etc.
– What varies is how quickly and how well the neurons communicate
with each other.
• Our brains can develop over time by forming new synapses with other
neurons.
Neural Connections
• Eventually, the brain starts to create connections (or pathways) between
the neurons, so things become easier and you can do them better and
better.
– Think back to the first time you rode a bike. Your brain had to think
about pedalling, staying balanced, steering with the handlebars,
watching the road, and maybe even hitting the brakes — all at once.
Hard work, right? But eventually, as you got more practice, the
neurons sent messages back and forth until a pathway was created in
your brain. Now you can ride your bike without thinking about it
because the neurons have successfully created a "bike riding"
pathway.
• Scientists think these “pathways” are created by a type of Glial cell called
the astrocytes!
Mirror Neurons
• Observing another person carrying out an
activity appears to be almost as effective as
carrying out the activity itself!
• Humans have the capability to mimic
observed behaviours without having to
“learn” them.
Neurons and Astrocytes
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We simply do not have enough neurons in the brain to deal with everything at
once.
If our neurons had to think about every little thing that we did, it would be all
too overwhelming. This is where the astrocytes come in.
If something happens numerous times the astrocytes say “let’s not think about
this” and we flick into an auto-pilot type of operation.
98% of life we are in a subconscious state – the astrocytes are working hard.
However astrocytes will re-engage the neurons extremely quickly if the
predictions that were made were not realised and you are instantly (almost)
brought into consciousness via the neurons now returning to run the process. Eg:
expecting a step to be there and it’s not – you get a shock.
Astrocytes
What are Astrocytes?
• Astrocytes are a form of glial cell.
• They make up 76 % total number of cells in the brain.
• Astrocytes:
– constantly watch neurons and are looking for recurring patterns releasing the
neurons to think consciously by managing the predictable events.
– simultaneously check which hormones are being produced by that pattern of
neural behaviour.
– say “don’t worry, we’ll do it – we’ll take care of it – don’t think about it.” This
frees up neurons for the thinking stuff/new learning stuff.
• For example: visualise how a young child problem solves as they try to sit
on a chair versus how we do it automatically. It takes about 2 years to
build the model of sitting on a chair to the point where the astrocytes will
take over and you no longer have to think about it.
• For example: Have you ever driven somewhere only to find that you can’t
remember getting there? Or any conscious thought as to your driving
skills? Your astrocytes are doing the thinking for you.
• Busy, non-purposeful work doesn’t produce more astrocytes because
they’re not needed.
Einstein…
• Einstein had 76% more astrocytes
than normal freeing up his neurons
to do a lot more thinking and
processing than the average person.
• This gives Einstein an incredible
capacity to build conceptual
frameworks of understanding.
• The capacity to take processes we do
every day and make them
unconscious allows for tremendous
efficiency in how our brains work.
• The higher your ratio of neural:glial
cells the higher your capacity for
intelligence.
• The Ratio of Neuron:Glia is
Humans 1:10
Monkeys 1:1