Question

Questions about Cellular Neurobiology

1. Be able to draw a growth cone and the key cytoskeletal structures within that we have discussed in class. What are the key properties of actin vs microtubules, and what about these properties makes them appropriate for their respective roles in neuronal growth cones (or neurons more generally)?

Answer 1

CYTOSKELETON: The internal framework of a cell composed of protein filaments and microtubules in the cytoplasm and has a role in controlling cell shape,maintaing intracellular organisation and in cell movement.

MICROTUBULES: They are tubular polymers of tubulin that form part of the cytoskeleton that provides structure and shape to the cytoplasm of cell.They are in the form of microtubule organising centers.

FUNCTION:

1. Chromosome segregation, transport,mobility and mechanical support
2. They can shrink and grow to generate energy due to presence of motor proteins
3. They facilitate the transport of organelles,vesicles and proteins along the apical-basal axis of the cell
4. vital role in cell migration

NEUROFILAMENTS: They are intermediate filaments made up of protein polymers. They are classified in 6 classes:

1. Class I and II - keratins
2. Class III - Vimentin, Desmin,Peripherin, GFAP
3. Class IV- neurofilament proteins L,M,H and Internexin
4. Class v - nuclear Lamins
5. Class VI - Nestin

FUNCTIONS:

1. Space-filling function to increase Axonal-diameter and their contriution is determined by number of neurofilaments in Axon and their packing density.
2. They work with microtubules and neurofibrils in transport of proteins.

MICROFILAMENTS: They are actin filaments and are composed of polymers of actin.

FUNCTIONS:

1. The strong and flexible arrangement of the microfilaments allows it to help with cell movement
2. They help in cytokinesis
3. Endocytosis and exocytosis
4. Cell Contractility
5. Mechanical stability and cell shape maintainance
6. They helps in Pullig Action in Muscle contration