Chapter 5- Development and Plasticity of the Brain Flashcards
Human Central Nervous system begins to form when the embryo is how old?
2 weeks
Brain weight at Birth
350 grams
Brain weight a 1 year
1,000 grams
Brain weight as an adult
1,200- 1,400 grams
Correct pattern of development of neurons ?
Proliferation, Migration, Differentiation, Myelination, Synaptogenesis
What is Proliferation?
Production of new cells.
What are Stem cells?
Cells that remain where they are, continuing to divide
What is Migration?
movement of cells after they have differentiated as neurons of glia , some migrate much faster than others
migration is guided by immunoglobins and chemokines
What is Differentiation?
process whereby neuron forms its axons and dendrites…axons grow first
What is Myelination?
process by which glia produce insulating fatty sheaths that accelerate transmission
myelin forms first in the spinal cord and then in the hindbrain, midbrain and forebrain and continues gradually for decades
What is Synaptogenesis?
formation of synapses. Begins before birth and continues throughout life
Can the adult vertebrate brain generate new neurons?
Only olfactory receptors and stem cells,
stem cells in interior of brain sometimes divide and create “ daughter” cells that migrate to olfactory bulb and transform inso glia or neurons
According to carbon dating, the human brain forms ____ new neurons in the cerebral cortex
few or none
How do axons find their targets with such precision?
they follow path of cells-surface molecules, attracted by some chemicals, repelled by others
What is Neural Darwinism?
as nervous system develops, we start with more neurons and synapses than we keep.
Axons make trial connections with many postsynaptic cells, and then each postsynaptic cell strengthens some synapses and eliminates others
Rita Levi- Montalcini discovered…
that muscles do not determine how many axons form, they determine how many survive
A neuron’s “ suicide program” is called
Apoptosis and is a programmed mechanism of cell death. Occurs if an axon does not make contact with an appropriate postsynaptic cell by a certain age
When a neuron forms synapse onto a muscle, muscle delivers a protein called
Nerve Growth Factor ( NGF)- which promotes survival and growth of axon
How does the CNS match the number of incoming axons to the number of receiving cells?
By the brain overproducing neurons and then applying apoptosis
What is a neurotrophin?
chemical that promotes survival and activity of a neuron ( NGF)
What is the most abundant neurotrophin in adult cerebral cortex?
Brain-derived neurotropic factor ( BDNF)
True or False. Each area of the brain has a period of massive cell death?
True
True or False. Apoptosis occurs throughout a person’s lifetime?
False, after maturity apoptotic mechanisms become dormant, except under traumatic conditions
What is Fetal Alcohol Syndrome?
a condition marked by hyperactivity, impulsiveness, difficulty maintaining attention, varying degrees of mental retardation, motor problems, heart defects and facial abnormalities
most dendrites are short with few branches