Synaptic communication Flashcards
Why is it odd that sodium does not pass through potassium channels?
- same charge when dissolved in water
- k+ is bigger than sodium
How did they study the specificities of potassium channels?
- mutated the nucleic acids in the ion channel proteins one by one and grew them on a frog cell
Why can Na+ not pass through potassium ion channels?
- in water, ions gain a hydration shell that stabilizes them and makes them bigger
- the micro-charges of the potassium channel are organized so that the potassium ion is more stable in the channel than in its hydration shell
- it will therefore leave its shell to join the channel
- BUT the Na+ ion is too small to have these ideal interactions with the carbonyle groups inside the pump. it keeps its shell and is therefore too big to enter the cell.
What is a promoter?
Region of DNA that initiates transcription of a particular gene
How does the action potential propagate?
- by causing a chain reaction of depolarization of the axon by puchinf positive ions always furhter toward the axon terminal
What is particular about the types of potassium channels a human has?
- there are more than 40 types of potassium channels
the number of channel of each type per cell partly determines the function of the neuron
What are glial cells?
lipids that surround all the cells in the brain
What are the functions of glial cells?
- help traffic nutrient
- help maintain molecular stability in the extracellular space
What is the most abundant component of the brain?
Glial cells
What is the quantity proportions between glial cells and neurons in the brain?
between 2:1 and 5:1
What are the three types of glial cells?
- Astrocytes
- Microglia
- Oligodendrocytes
Where are the glial cells situated?
Exclusively in the central nervous system
What are the roles of astrocytes?
- physical support
- cleans up debris in the brain and break it down
- provides scaffolding for various cellular functions
- control the chemical composition of the inter-neuronal space
- helps nourish neurons
What is the role of microglia?
- responsible for the immune system of the brain that is independent from that of the rest of the body
- protect the brain from invading micro-organisms
What are the roles of oligodendrocytes?
- create myelin sheath
- can myelinize 50 neurons
What glial cell is the janitor of the cell?
Astrocytes
What glial cell is responsible for the brain’s immune system?
Microglia
What glial cell is responsible for myelination?
oligodendrocytes
How many axons can one oligodendrocyte myelinate?
50
What is the structure of the myelin sheath?
- the myelination is 20 microns
- the node of ranvier is 1 micron
What is saltatory conduction?
How is the action potential propagated through the axon?
- through saltatory conduction
What is the impact of the presence of a sheath of lipids around the axon?
- no electrostatic interaction with the environment is possible, as the axon is insulated. the transport is therefore faster.
What is the impact of the presence of nodes of ranvier in the myelin sheath?
- allows the regeneration of the electric charge (the charge is renewed). The transport is therefore more efficient (no loss of charge)
Where does the axon enter in contact with extracellular fluid?
at the node of ranvier
On the axon, where are the ion channels?
At the node of Ranvier