Lecture 3: Neuronal axon and synapse Flashcards
How are proteins and other macromolecules transported along the axon?
They are transported by motor proteins attached to the cytoskeleton.
Which organelle do synapses have many of and why?
Mitochondria, because the synapses require lots of energy.
What are microtubules in the neuronal axon capable of moving and do these need to be moved?
Proteins, mitochondria (synapses require lots of energy), vesicles (need to be close to pre-synaptic membrane), mRNAs (moved to local set-ups with ribosomes where you need to synthesise proteins).
What on the neuronal axon microtubules moves the macromolecules and organelles away from the cell body?
A plus-end directed kinesin motor protein
What is anterograde?
The ‘forward’ movement of macromolecules/organelles away from the cell body.
What is retrograde and which motor is responsible?
The ‘backward’ movement of macromolecules/organelles towards the cell body. Often, this involves the movement of damaged organelles which need to be degraded near the cell body. The motor responsible is dynein.
What are MAPs? Give an example of one.
Microtubule-associated proteins, e.g. Tau
How is Tau regulated?
Phosphorylation
What is the clinical relevance of microtubules in neuronal axons?
MAP Tau can be hyperphosphorylated, causing the formation of insoluble aggregates. This can cause Alzheimer’s disease, is associated with Down syndrome and dementia.
Dynein mutations cause a slow, progressive form of motor neurone disease called ‘distal Hereditary Motor Neuropathy’. This causes the neurons to work less and less efficiently as the person ages.
How many synapses does one neuronal axon have?
1000 to 10,000. Certainly more than the one that is normally show in textbooks. In fact, dendrites of neurones can receive information from more than one synapse with another cell at once, and has to decide which to ‘listen to’.
Describe an electrical synapse.
Electrical synapses are quite rare (usually synapses are chemical). They are used in development, when neurons need to be connected quickly. They occur when two neurons are connected by gap junctions, so the direct flow of ions is allowed.
How are vesicles primed for release?
The vesicles are positioned very close to the pre-synaptic membrane and often their snares are already tangled with the pre-synaptic membrane snares.
What is the post-synaptic density?
Dense neurotransmitter receptors and cytoskeletal mesh. They are specialised for the reception and transduction of neurotransmitter signals.
What is the connectome?
All of the connections made by neurones in the brain. It is currently being mapped (blue brain project).
How are synapses formed?
The axons of neurones grow outwards, exploring, being guided by the growth cone (microtubules and actin) and filapodia (actin-based), both of which are finger-like projections with test the environment.
