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Summary lectures Nutrition and The Brain (HNH-31706)
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This document contains a comprehensive summary of all lectures in the Nutrition and the Brain course.
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Nutrition and the BrainLecture 1: basic principles of brain function
Basic brain function & anatomy
- Brain tissue:
o Neurons (100 billion) supported by glia cells
- Glia cells
o Astrocytes (Central nervous system (CNS), support) → prone in supporting neurons
o Oligodendrocytes (CNS, myelin, action potential) → produce myeline around axon of neuron
o Microglia (CNS, neuroinflammation) → immune system of the brain
o Ependymal cells (CNS, ventricles, cerebrospinal fluid) → form the outer layer of the brain, also
inside the ventricles
o Schwann cells (Peripheral nervous system (PNS), myelin in spine)
o Satellite cells (PNS, support in spine)
Neurons
There are different types of neurons. Multipolar neurons
are the most common in the brain. It consists of
dendrites where the signals enter. A cell body accepts
the signal and decides if he wants to proceed sending
the signal to another neuron, making an action potential.
If the cell body decides to proceed the signal, this action
potential hops from the node of Ranvier to the axon
towards your synapse. These synapses are at the end of
the axon. The axon is covered with myeline.
How you can distinguish between the different types
- Astrocytes: really connected to neurons with little feet’s, they project on this neuron so they can
communicate with this neuron but also send signals or sense glucose levels within these neurons
- Oligodendrocytes: produces myeline, the oligodendrocytes are sort of in the middle of these myeline
structured fibers
- Microglia: small, not really connecting, they can change more when there is a level of inflammation or
stress in the brain
- Ependymal cells: in the outer layer and in the ventricles, they produce along with choroid plexus
cerebrospinal fluid (CSF) → You have approximately 150 ml of CSF flowing through your brain and it is
refreshed four times a day
- In your PNS you have the satellite cells (responsible for the support within your spine) and the
Schwann cells (responsible for the myelin within your spine)
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,Neuronal communication between each neuron
- Synaptic transmission (neurotransmitters, pre-postsynapses)
- Action potential (Na/K-pumps, membrane potential)
An action potential goes from the cell body towards the axons towards the synapse. They come at the bottom
of the synapse, there are synaptic vesicles filled with neurotransmitters (like dopamine and serotonin). When
an action potential reaches the synapse, these vesicles dock towards the membrane and release the
neurotransmitters into the synaptic cleft. When it is in the synaptic cleft, it can reach the dendrite of other
neurons and it can decide if it is enough stimulating to proceed towards the cell body with the signal and
proceeding with the action potential.
Dopamine is related to Parkinson’s disease and addiction. Serotonin is related to depression. Most of the time
you have these neurotransmitters within your body but they cannot cross the blood brain barrier (BBB), so
precursors cross the BBB and they are transformed into neurotransmitters within your brain.
Neurotransmitters or precursors obtained by diet
Neurotransmitter release
- Syntaxin→ docking of the synaptic vesicle towards the membrane of the synapse (syntaxin is a protein
of the synaptic vesicles)
An action potential is coming from above and guided through the axon towards the synapse. If the action
potential reaches the synapse, there is membrane depolarisation and this results in a Ca2+ influx, Ca2+ influx is a
signal to the vesicles (synaptic vesicle contains neurotransmitter). Via certain proteins this leads to docking
and opening up of the vesicles into the synaptic cleft and release of the neurotransmitters. When these
neurotransmitters are released, they can bind on the post synaptic cell to a receptor. If enough
neurotransmitters are bind, again a Ca2+ influx and action potential proceeds towards the cell body of another
neuron. When the neurotransmitters are released in the synaptic cleft, they are up taken in the pre-synapse
again. For example cocaine blocks the reuptake receptors so a high level of dopamine is left in the synaptic
cleft really stimulating the receptors. That
is provoking the effects of cocaine.
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, Instant synthesis
You have another way of neurotransmission between for example neurons and astrocytes: endocannabinoids.
It can be instantly formed, when an action potential arrives at the pre synapses, a neurotransmitter is released
at the post synapses and if necessary, endocannabinoids can be formed from the cell membrane and then you
can get different kinds of signalling, you can go back to the pre synapse but also to the astrocytes.
Endocannabinoids are involved in addiction and food preference.
Neuronal communication
Synaptic plasticity
- After long term potentiation (LTP), synaptic communication is strengthened
- Base of learning and memory processes, if you learn you repeat a certain times and a certain pathway
is stimulated every time. The synapse changes a bit, it adapts to your system.
- Challenge and stimulate your brain, else synapses degenerate
- If you start learning you don’t remember that much, after a few times the synapse is changed towards
a learning process and if you want it in your memory, the synapses are solid connected to each other.
You have more synapses in a certain direction, they don’t degrade anymore, they just stay at that
position and in the learning process they can change in position and alter a bit. It is a flexible process.
- If you repeat the stimulation, the vesicles and receptors increase and can even lead to alternations in
where the synapse is project and if you repeat long enough, the change become stuck/solid and then
it is a sort of memory part.
Brain tissue
To show how all the cells types are interconnected with each other and working together.
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