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Full Summary for Food and Brain health

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Radboud Universiteit Nijmegen (RU)

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food
brain
health
brain structure
brain health
brain basics
brain function
cognitive ageing
gut brain axis
lifestyle and brain
immune b
interventions in brain disease
role of nutrition in brain health

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Food and Brain Health Lecture 1
Brain Basics – Dr. Ilse Arnoldussen

Neurons and Glial Cells
Neurons, White and Grey Matter
Humans have about 87 billion neurons.

Neurons have a cell body containing a
nucleus, mitochondria and ER. It contains
dendrites, from which it receives signals, and
an axon, which it uses to transport signals to
other cells. At the synaptic cleft, the
neurotransmitters are released from the axon
terminal, and reach the receptors on the
dendrites, for example.

White matter mainly consists of a lot of axons (the myelin on the axons gives it its white
colour), whereas grey matter mainly consists of cell bodies. Grey matter is commonly
found on the cortex of the brain.

The nuclei deep inside the brain are considered grey matter and serve to integrate the
motor commands with the social and spatial environment (without, for example, we’d
be constantly bumping into things, or the movements aren’t smooth).

Astrocytes and Microglia in Neuro-inflammation
The human body has
about 1 trillion glial
cells (10 glial cells per
neuron, 1 capillary per
neuron). The most
common glial cells are
astrocytes. Microglia
are only found in the
brain. Ependymal
cells are found in the
brain and the central
canal in the spinal
cord. They are found
near the cavities.

,Astrocytes and microglia are involved in neuroinflammation.

Neuroinflammation can be initiated by a variety of cues (e.g. infection, brain trauma,
toxic metabolites, oxidative stress, etc.). Chronic neuroinflammation (e.g. brain injury,
aging, viruses, toxic metabolites) results in sustained activation of glial cells and
recruitment of other immune cells into the brain. This is associated with
neurodegenerative diseases.

Astrocytes and the Blood-Brain-Barrier
The BBB is mainly formed out of astrocytes and serves to protect the brain from harmful
substances. In order to enter the brain, molecules can diffuse across membranes (e.g.
oxygen and other gasses, as well as lipid-permeable compounds) or they can be
transported by transporters. A high electrical charge slows down diffusion across
membranes.

The BBB is involved in neuroinflammation, in which there is an increased permeability
in the BBB. This can also happen in neurodegenerative diseases or other diseases, such
as diabetes and obesity.

Brain Metabolism
The brain is about 2% of the body weight and consists for 60% out of lipids. 20% of all
glucose-derived energy in the body comes from the brain, making energy demand of the
brain very high (about 5.6 mg glucose per 100 g human brain tissue per minute).

,Glucose
Astrocytes and oligodendrocytes contain Glut-1 transporters; neurons contain Glut-3
transporters. The endothelial cells of the BBB transport the glucose via GLUT1 into the
space with astrocytes, neurons, etc. There,
the glucose can be used or stored for neurons
by astrocytes. Neurons can also directly take
up glucose (higher affinity than GLUT1). In
case of low glucose levels in the brain, the
astrocytes will release lactate, which is
formed from their glycogen storage. This
lactate is metabolized by neurons and
oligodendrocytes. At high glucose levels in
the brain, glycogen will be stored by
astrocytes.

Circulation
As mentioned above, each neuron requires one capillary to function.

Arteries

The circle of Willis serves as a backup/rescue mechanism, to constantly provide the
brain with blood. One method of blood supply is through the vertebral artery -> the
basilar artery -> the posterior cerebral artery, middle cerebral artery and anterior
cerebral artery. Another method is through the internal carotid artery, which runs from
the neck and enters the circle of Willis just behind the eyes. Different parts of the brain
are supplied by different arteries (see image below).

, Veins
The superior
sagittal sinus
runs all the way
along the top of
the brain, in
between the two
hemispheres.
Blood is supplied
from the bottom
and removed
from the top. This
allows it to stay
floating in the skull.

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