Chapter 23 - Construction of Neural Circuits. Flashcards
What are polarized epithelial cells?
Polarized epithelial cells is a class of cells found in most tissues. Neurons belong to this group.
Why are polarized epithelial cells polarized?
Polarized epithelial cells are usually specialized for living on the border of different environments, and therefore have distinctions between their apical and basal surfaces. These distinctions arise from the differential distribution of proteins that constitute the cellular cytoskeleton.
How does the initial growing of neuronal processes look?
Initially, a number of apparently equivalent small extensions (referred to as neurites) protrude from the immature neuron. Soon after, microtubule and actin components of the cytoskeleton as well as other proteins are redistributed among the neurites so that a single process is identified as the axon.
In terms of cell polarity, which part of the neuron is apical and which is basal?
The axon is the apical domain, and the dendrites are the basal domain.
A number of studies have implicated a particular protein family as necessary for the development of axons. Which family?
Proteins of the PAR protein family (“partitioning defective”). When the function of PAR proteins or related signaling molecules is disrupted, the specification of a single axon does not occur.
Dendrites extend using mechanisms that are similar or different to those of axons?
The manner in which dendrites extend is similar to that of axons.
A specialized structure at the tip of the extending axon .. what is it called?
It is called the axon’s growth cone.
What is the primary morphological characteristic of a growth cone?
The primary morphological characteristic of a growth cone is a sheetlike expansion of the growing axon at its tip.
The primary morphological characteristic of a growth cone is a sheetlike expansion of the growing axon at its tip. What is this sheetlike expansion called?
The primary morphological characteristic of a growth cone is a sheetlike expansion of the growing axon at its tip called a lamellipodium.
When growth cones are examined in vitro, lamellipodia can be seen clearly. What would we also be able to discover?
That each lamellipodia has numerous fine processes called filopodia.
Ever since Santiago Ramón y Cajal’s observations in the early 1900s, changes in growth cones have been observed to occur. What changes, and why?
The lamellipodium of the growth cone expands. It is thought that this happens as the growth cone enters a critical “decision point”, where it needs to “scout ahead” to determine the right trajectory for growth.
In what way does the actin cytoskeleton contribute to axon growth?
The actin cytoskeleton regulates changes in lemallipodial and filopodial shape for directed growth.
In what way does the microtubule cytoskeleton contribute to axon growth?
The microtubule cytoskeleton is responsible for the elongation of the axon itself.
What determines synapse formation?
Adhesive, attractive and repulsive molecules - such as we see influence growth cone motility, also influence the differentiation of growth cones into synapses.
