Ch5-Dev & Plasticity of the Brain Flashcards
Human central nervous system begins to form when the ______ is ____ old.
embryo (0-10weeks)
2 weeks
What are the 5 stages of growth and development of neurons?
proliferation migration differentiation myelination synaptogenesis
responsible for the production of new cells (stage 1 of growth & dev of neurons)
proliferation
responsible for the movement of cells after they have differentiated as neurons or glia (stage 2 of growth & dev of neurons)
migration
the process whereby neuron forms its axon and dendrites (stage 3 of growth & dev of neurons)
differentiation
the process by which glia produce insulating fatty sheaths that accelerate transmission (stage 4 of growth & dev of neurons)
myelination
responsible for the formation of synapses [neurons separate] (stage 5 of growth & dev of neurons)
synaptogenesis
Roger Sperry discovered what when studying newts?
axons find their targets by following chemical pathways; it is attracted by some pathways and repelled by others
as the nervous system develops, we start with more neurons and synapses than we can keep
[some synapses are strengthened while others are eliminated]
Neural Darwinism
Levi-Montalcini discovered ______
muscles do not determine how many axons form; they determine how many survive
a neuron’s suicide program: if its axon does not make contact with an appropriate postsynaptic cell by a certain age, the neuron will kill itself
[programed mechanism of cell death]
apoptosis
why does the brain overproduce neurons, then apply apoptosis?
this enables the CNS to match the number of incoming axons to the number of receiving cells
chemical that promotes survival & activity of neurons
neurotrophin
what would happen if apoptosis was interrupted?
the brain would keep growing
name 2 types of neurotrophins
nerve growth factor [ngf]
brain-derived neurotrophic factor [bdnf]
what is the most abundant neurotrophin in adult CNS?
brain-derived neurotrophic factor [bdnf]
when a neuron forms synapse onto a muscle, the muscle delivers a protein called ______.
[promotes survival & growth of the axon]
nerve growth factor [ngf]
when does apoptotic mechanisms become dormant, except under traumatic conditions [ex) stroke]?
after maturity
what can affect the early stages of brain development?
malnutrition
toxic chemicals
infections
condition marked by hyperactivity, impulsiveness, difficulty maintaining attention, varying degrees of mental retardation, motor problems, heart defects, & facial abnormalities {caused by the mother consuming large quantities of alcohol before birth]
fetal alcohol syndrome
how do neurons in different parts of the brain differ?
in their shape & chemical components
how does a neuron decide which type of neurons it’s going to be?
- immature neurons experimentally transplanted from one part of the developing cortex to another develop the properties characteristic of their new location
- neurons transplanted at slightly later stage develop some new properties while retaining some old ones
axons & dendrites continue to modify their structure throughout life; what is the implication of this?
indicates new connections (learning) and the turnover of synapses
Neuronal changes are guided by experience; rat in enriched environment vs deprived environment?
enriched = more dendritic branches deprived = less dendritic branches
neurons become more _____ and more _____ to stimuli that have been important or meaningful in the past
responsive; finely tuned
What happens to the brain if a sensory system is impaired?
the part of the brain that would normally aid that sensory system aids a different sensory system to compensate
[losing a sense does not affect sense receptors of other sense organs; it increases attention to other sense organs, which causes the brain to adapt to that attention]
2 hypotheses of musicians
1) practicing a skill reorganizes the brain to maximize performance of that skill
2) people who already had certain cognitive skills & brain features are more likely than others to become musicians
- cortical areas map an overlap of 2 fingers
- result of extensive reorganization of sensory thalamus & cortex
- touch responses on one finger overlap to another finger
focal hand dystonia
musician’s cramp, writer’s cramp
voluntary movement away from normal direction (children under 7 do not have enough control to complete this task)
antisaccade task
adolescents have a tendency to discount the future and be impulsive this is due to……
their brains anticipating rewards and being unable to inhibit behaviors
What happens to the brain after age 60?
- neurons alter synapses more slowly
- thickness of temporal cortex shrinks
- volume of hippocampus gradually declines
- cerebral cortex begins to thin at age 30
major cause of brain injury in young adults
closed head injury [sharp blow to head that does not puncture brain
temporary loss of blood flow to a brain area (common cause of brain injury in elderly)
stroke (cerebrovascular accident)
2 types of stroke
ischemia & hemorrhage
stroke that is the result of blood clot or other obstruction in artery; neurons are deprived of blood & lose much of their oxygen & glucose supplies
ischemia
stroke that is the result of a ruptured artery; neurons are flooded with blood & excess oxygen, calcium, & other chemicals
hemorrhage
stroke causes _______, an accumulation of fluid, which increases pressure on brain & probability of additional strokes
edema
ischemia & hemorrhage impair _____
the sodium-potassium pump
[ch5 pt2] (causes overstimulation of neurons, leading to excess positive ions blocking metabolism in mitochondria and killing the neurons)
best immediate treatment for stroke (since most common type is ischemia)
tpa=tissue plasminogen activator - breaks up blood clots
decreased activity of surviving neurons after damage to other neurons
diaschisis
although a destroyed cell body cannot be replaced, damaged axons can _______ under certain circumstances
grow back
after loss of a set of axons, cells that lost their source of innervation react by secreting neurotrophins to induce other axons to form branches called _____
collateral sprouts
heightened sensitivity to a neurotransmitter after the destruction of an incoming axon; helps compensate for decreased input
denervation supersensitivity
heightened sensitivity as a result of inactivity by an incoming axon
disuse supersensitivity
continuing sensation of an amputated body part; can range from tingling to intense pain
phantom limb
[this is due to the reorganization of cells in the cortex]
a limb that has lost its afferent [sensory] input
deafferented limbs [is still usable but more difficult]
