1.3. Neuronal Transport

Question 1

What is the significance of axonal transport in healthy nerve cells?

Answer 1

Axonal transport is crucial in healthy nerve cells as it manages the intracellular movement of molecules and organelles. Components produced in the soma are distributed to other cell compartments, and constituents from dendrites and axons need to be transported to the soma.

Question 2

How is axonal transport compared to railways in a neuron?

Answer 2

Axons are likened to railways in a neuron, where motor proteins act as trains, transporting cargos such as vesicles and proteins along microtubule tracks in both anterograde and retrograde directions.

Question 3

Fast Anterograde Transport

Answer 3

(100-400 mm/day):Transports organelles, vesicles, neurotransmitter precursors, enzymes, and macromolecules to the axon terminal using kinesin on microtubules.

Question 4

Slow Anterograde Transport

Answer 4

(0.25-5 mm/day): Involves slower transport of soluble and cytoskeletal proteins using kinesins with a “stop and go” mechanism.

Question 5

Fast Retrograde Transport

Answer 5

Transports materials for degradation or recycling back to the soma using dynein on microtubules. It also conveys chemical signals to the soma, and viruses like herpes simplex and polio can exploit this route to reach the CNS.

Question 6

How are neuronal tracing techniques used to study neuronal morphology and connections?

Answer 6

Neuronal tracing involves anterograde and retrograde techniques. Anterograde tracing uses microinjection of fluorescent dyes taken up by the cell body, while retrograde tracing involves microinjection of substances like enzymes or viruses, which are taken up by axon terminals and transported retrogradely to the soma.

Question 7

What happens in cases where axonal transport is compromised, and what conditions are associated with such compromise?

Answer 7

Axonal transport is compromised in diabetic neuropathies, Amyotrophic Lateral Sclerosis (ALS), and is implicated in Parkinson’s and Alzheimer’s Diseases. Axonal injury, leading to “Wallerian degeneration,” interrupts transport, and in the CNS, regrowth is limited due to factors like myelin production by oligodendrocytes and astrocyte-induced scarring.