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20 Cards in this Set

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what is the earliest development of the nervous system?
18 days. the ectoderm begin to form a plate
21 days after conception what begins to form in the development of a nervous system?
The neural tube.
The first major division to form chambers makes what regions of the brain.
Forebrain, midbrain and the hindbrain.
The second division occurs only in the forebrain and forms what?
3 sections: 2 lateral ventricles and the third venrtricle.
What gives rise to the cells of the CNS?
The ventricular zone. In other words the cells that line the inside of the neural tube.
How do studies show the cerebral cerebral cortex develops?
Using radioactive tracking, it seems that the cortex develops outward radially. Neuronal growth begins at the ventricular zone and grows out radially.
What guides the growth of neurons out from the ventricular zone?
Radial glia- fibers that extend out radially and function to attach to the surface of the cortex and guide neurons to their resting places.
The cells in the ventricular zone that give rise to neurons are called?
Founder cells
There exists 2 forms of neuronal growth list the 2 and characterize them:
1.) Symmetric division- the early part of division where the founder cells divide to form an exact copy of itself.

2.) Asymmetric growth- this is where a founder cell divides in to another founder cell and a neuron which is free to migrate (with the help of radial glia) outward from the ventricular zone toward the cortex.
How does the brain know to stop neuronal radial growth?
After a point, the neurons that migrate to form further regions of the brain, are killed by a cellular process apoptosis.
What do neurons then begin to do once they have migrated?
They begin to interconnect. neurons grow axons and dendrites to others and form terminal buttons. This process seems to be guided by chemical signals as neuronal growth has a tendency to grow in the direction of other particular neurons.
What regulation (aside apoptosis to neuronal growth?
the ventricular zone creates an excess amount of neurons. Neurons must form connections in a cell to live. There is a signal generated through to "connected" neurons necessary for life and those that have not been connected die off. (Evolution of neurons)
How do parts of the brain become specialized?
some is obviously genetic.

Studies show axons have some input into specialization. In opossum a piece of the cerebral cortex was removed before complete development. Post development the brain appeared to have all its regions just squeezed into the available space. "thus the growth of axons from thalamus to cortex appears to effectthe development of the region they serve.
Other than genetics and axon growth what can influence the neuronal growth in the brain?
Experience. Evidence indicates that a certain amount of rewiring can even be accomplished in adulthood.

examples: amputee, string musicians,
What is neurogenesis? Does it or doesnt it occur?
Neurogenesis is the production of neurons in the fully developed brain. Recent studies show it does occur.
How does neurogenesis occur?
Even the adult brain has some stem cells that can divide and form neurons much like founder cells do.
Eventhough research shows neurogenesis can occur no evidence has shown... what?
that it can replace the neuronal circuitry that have been destroyed by injury, stroke, or disease.
What is genetic duplication? what has it been credited with? How does this work?
Genetic duplication is believed to be a major method for the evolution of the human brain. Geneticists are finding that genes can reproduce themselves to keep one gene functioning normal and experiment with the other.
Other than genetic duplication, what is another explanation for the evolution of the human brain?
Master genes. Evolution and more complexity in master genes has led to a more complex brain in humans overall. Master genes are genes that control many other genes and thus have an appreciable of control.
Why does prolonged pregnancy in humans help account for the evolution of the human brain?
The size of the brain increases during symmertical and assymetrical growth. Thus longer times in these periods (which is found to be true in humans) gives rise to more neuronal growth and therefore larger brains.