What do microtubules do in axons?

Microtubules (MTs) are long cylindrical structures of the cytoskeleton that control cell division, intracellular transport, and the shape of cells. MTs also form bundles, which are particularly prominent in neurons, where they help define axons and dendrites.

Are microtubules found in the axon?

Axons have tau-bound microtubules of uniform orientation, whereas dendrites have microtubule-associated protein 2 (MAP2)-bound microtubules of mixed orientation. Dendrites also contain organelles that are not found in axons, such as rough endoplasmic reticulum, polyribosomes and Golgi outposts.

What is axonal hillock?

The axon hillock is a specialized part of the cell body (or soma) of a neuron that connects to the axon. It can be identified using light microscopy from its appearance and location in a neuron and from its sparse distribution of Nissl substance.

Which type of cells form the myelin sheaths around axons of a neuron?

Myelin is formed by Schwann cells in the peripheral nervous system (PNS) and oligodendrocytes in the central nervous system (CNS). Each Schwann cell forms a single myelin sheath around an axon. In contrast, each oligodendrocyte forms multiple sheaths (up to 30 or more) around different axons (Figure 1).

What role do microtubules play in neuronal processes?

Microtubules play important roles in many cellular functions, including neuronal morphogenesis. During neuronal development, microtubules must form stable bundles, which grow and reorganize to provide the main structural framework for the shafts of axons and dendrites.

How do microtubules assemble and disassemble?

The centrosome serves as the initiation site for the assembly of microtubules, which grow outward from the centrosome toward the periphery of the cell. This can be clearly visualized in cells that have been treated with colcemid to disassemble their microtubules (Figure 11.40).

How many microtubules does an axon have?

Axons can have as many as 100 bundles of microtubules in one axon cross section. There are many variations in these lattices with different types of stabilizing molecules, different orientations, and many different associated molecules and co factors.

Is axon hillock the axon terminal?

The bridge between the cell body and the axon is known as the axon hillock. The generation of the action potential occurs at the axon hillock. Most of the neurons possess one key axon and multiple dendrites. The terminal point of the axon is the presynaptic terminal (also referred to as terminal bouton).

What happens in axon hillock?

Learn about this topic in these articles: …at a region called the axon hillock, or initial segment. This is the region where the plasma membrane generates nerve impulses; the axon conducts these impulses away from the soma or dendrites toward other neurons.

What supports the myelin sheath in the CNS and PNS?

Myelin is made by two different types of support cells. In the central nervous system (CNS) — the brain and spinal cord — cells called oligodendrocytes wrap their branch-like extensions around axons to create a myelin sheath. In the nerves outside of the spinal cord, Schwann cells produce myelin.

How does the myelin sheath differ between the CNS and the PNS?

Myelination provides the electrical insulation of neurons. In CNS (central nervous system) oligodendrocyte is responsible for myelination of neuronal axons. These cells have processes that wrap around the axons to form myelin sheath. In PNS (peripheral nervous system) myelin sheath is formed by Schwann cell.

Which of the following is known to sever microtubules during neuronal development?

The best known of the microtubule-severing proteins are katanin and spastin, both of which have a preference for stable domains. Live-cell imaging of cultured neurons has now revealed that microtubules moving in these axons are very short relative to the range of microtubule lengths within the array.

What is the difference between microtubule organization between axons and dendrites?

However, microtubule organization differs between axons and dendrites in at least two major aspects ( Fig. 1 ). First, orientation: axonal microtubules have uniform orientation, with their plus ends facing the axon tip, whereas dendritic microtubules have mixed orientation, with their plus ends facing either the cell body or the dendritic tip.

What is the difference between microtubules and maps?

Second, microtubules differ in their complement of MAPs: for example, MAP2 is found mostly in dendrites and tau is found mainly in axons. Figure 1: Microtubule organization and organelle distribution in axons and dendrites.

What is the function of microtubules in neurons?

Microtubules form dense parallel arrays (bundles) in axons and dendrites that are required for the growth and maintenance of these neurites.

How does microtubule assembly and stabilization in one neurite determine polarization?

Thus, it has now been established that local microtubule assembly and stabilization in one neurite is a physiological signal that specifies neuronal polarization, and that changing microtubule dynamics is sufficient to alter axon and dendrite specification and development.