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Cellular and Molecular Neuroscience - Coggle Diagram
Cellular and Molecular Neuroscience
The Blood Brain Barrier (BBB)
Guardian against toxins
Prevents harmful substances, pathogens and large molecules from entering the brain
Selective gatekeeper
Allows the passage of essential nutrients, oxygen, and hormones while restricting others
BBB
Term used to describe the unique properties of the microvasculature of the CNS
Formed by brain capillary endothelial cells (BCECs) lining neurovasculature
BCECs surrounded by pericytes and astrocytic endfeet
Unique properties of BCECs restrict access of blood borne substances
BCECs tightly joined together restricting entry of substances
Properties allow BCECs to tightly regulate movement of molecules, ions, and cells between blood and CNS
Together cells of BBB make up neurovascular unity (NVU)
Carrier Mediated Transcytosis
Molecules like glucose, are carried across the BCECs via specific solute carriers/carrier proteins
Solutes (e.g. glucose) will bind to protein transporter
This will lead to conformational change
Carrier will then transport substance to other side of membrane
Usually from high to low concentration
If against concentration gradient, requires ATP to provide the energy to facilitate the process
Absorptive Mediated Transcytosis
Positively charged molecules like L-DOPA enter the brain via absorptive mediated transcytosis
Positively charged substance in bloodstream associate with negatively charged membrane surface
This induces membrane invagination and vesicle formation
Substance-containing vesicle will enter intracellular space
Move to other (abluminal) side and release contents
Receptor Mediated Transcytosis
Macromolecules (e.g. insulin, transferrin) enter via receptor binding which triggers an endocytotic event and subsequent transportation across the BBB
Ligand binds to receptor
Initiates invagination of membrane and endocytosis process
In the cell the vesicle can be:
recycled back out into capillary
Fuse with membrane on other side allowing for content release
Fuse with lysosome and be degraded
BBB is major obstacle preventing life-saving treatments from reaching the brain
Treatments for various CNS diseases limited because of BBB permeability
treatments may exist but just can't pass BBB due to their characteristics
Astrocytes
Now BBB restricts access to many things but will act as a gatekeeper
Great structure to have given the sensitivity of brain tissue
There are different ways substances cross the BBB
Notice though that the BBB/neurovascular unit (NVU) has this thing called astrocyte endfeet
These are part of another cell in the brain called the astrocyte (another type of glial cell)
Astrocytes provide nutritional support to neurons. One astrocyte can make contact with thousands of neurons. Provides nutritional support to neurons, but not the only thing.