powerpoint 4.2 Development Of The Brain Flashcards
(Maturation of the vertebrate brain)
The human central nervous system begins to form when the embryo is approximately how many weeks old?
- the dorsal surface thickens, forming a neural tube surrounding a fluid filled cavity
- the forward end enlarges and differentiated into the…? H…….., m……., and f……..
- the rest of the neural tube becomes the…?
Two weeks old
Hindbrain, midbrain, and forebrain
Spinal cord
Brain development depends upon (2) M, L
We can refine this understanding by learning how..? (3)
N d, a c, e m d
Maturation and learning
Neurons develop,
their axons connect,
experience modifies development
(Cerebrospinal fluid)
The fluid-filled cavity becomes the central canal of the…? And the four…?
Spinal cord and the four ventricles of the brain
(Brain weight)
At birth the human brain weighs..?
By the first year. The brain weighs…?
The adult brain weighs..?
Approximately…
350 grams
1,000 grams
1,200-1,499 grams
The development of neurons in the brain involves the following processes:
- pro……….
- mig……
- diff………..
- myel…….
- synap………
Proliferation
Migration
Differentiation
Myelination
Synaptogenesis
(Proliferation)
The production of…? In the brain primarily occurring in…?
The production of new cells/neurons in the brain primarily occurring early in life
- early in development, the cells lining the ventricles divide
- some cells become stem cells that continue to divide
- others remain where they are or become neurons or glia that migrate to other locations
Migration
The movement of the newly formed n…… And g… To their eventual locations
Occurs in a variety of directions throughout the..?
Neurons and glia to their eventual locations
-some don’t reach their destination until adulthood
Brain
-chemicals known as immunoglobulins and chemokines guide neuron migration
Differentiation
The forming of the axon and dendrites that gives the neuron its….?
The axon grows first either during migration or once it has reached its target and is followed by the development of….?
Distinctive shape
The dendrites
Myelination
The process by which glia produce (what) that covers the axons of some neurons
- myelin speeds up the…? Of neural impulses
- First occurs in the…? And then in the..?
- occurs gradually for how long?
The fatty sheath that covers the axons of some neurons
- speeds up the transmission of neural impulses
- first occurs in the spinal cord and then in the hindbrain, midbrain, and forebrain
- decades
Synaptogenesis
The final stage of neural development-
The formation of the s……. Between n……
- occurs throughout the life as neurons are constantly forming n.. C………. And d……… O.. O…
- when does it start to slow?
Formation of the synapses between neurons
- occurs throughout the life as neurons are constantly forming new connections and discarding old ones
- slows significantly later in the lifetime
(New neurons later in life)
Originally believed that no new neurons were formed after…?
Later research suggests otherwise:
-stem cells: undifferentiated cells found…? That generate “daughter cells” that can transform into g… Or n……
New olfactory receptors also continually replace..?
Early development
Found in the interior of the brain that generates “daughter cells” that can transform into glia or neurons
New olfactory receptors also continually replace dying ones
(New neurons later in life cont.)
Development of new neurons also occurs in other…?
Stem cells differentiate into new neurons in the adult hippocampus of mammals and facilitate…?
Brain regions
-example: songbirds have a steady replacement of new neurons in the singing area of the brain
Learning
(The lifespan of neurons)
Different cells have different average…?
Skin cells are the newest. Most are how old?
Heart cells tend to be as old as..?
Mammalian cerebral cortexes form few or no new neurons after..?
Life spans
Under a year old
As old as the person
Birth
(Pathfinding by axons)
Axons must travel great distances across the brain to form the c…… C……….
Sperry’s (1954) research with newt’s indicated that axons follow a chemical trail to…?
Growing axons reach their target area by following a gradient of chemicals in which they are attracted by some chemicals and…? By others
Correct connections
Follow a chemical trail to reach their appropriate target
Repelled by others
(Competition among axons as a general principle)
When axons initially reach their targets, they form synapses with several c….
Postsynaptic cells strengthen connection with some cells and eliminate….? With others
The formation or elimination of these connections depends on the pattern of input from…? I……. A….
Several cells
Eliminate connections with others
Incoming axons
(Neural Darwinism)
Some theorists refer to the idea of the selection process of neural connections as…? N….. D……..
In this competition among synaptic connections, we initially form more (what) than we need
The most successful axon connections and combinations survive while others fail to sustain a….. s…….
Neural Darwinism
More connections than we need
Fail to sustain active synapses
(Determinants of neuronal survival)
Levi-montalcini discovered that muscles do not determine how many a…. form. They determine how many s……
Nerve growth factor (NGF)- is a type of protein released by muscles that promotes the s……. And g….. Of axons
-the brains system of overproducing neurons and then applying apoptosis enables the exact matching of the number of i……. A…. To the number of receiving cells
How many axons form; they determine how many survive
Promotes the survival and growth of axons
-the brains system of overproducing neurons and then applying apoptosis enables the exact matching of the number of incoming Axons To the number of receiving cells
(Neurotropins)
Are chemicals that promote the s……. And a……. Of n…… (NGF)
–axons that are not exposed to neurotropins after making connections ungergo…? A……..
-therefore, the healthy adult nervous system contains no neurons that failed to make…? A………. C……….
Chemicals that promote the survival and activity of neurons
- apoptosis: a preprogrammed mechanism of cell death
- appropriate connections
(Neuronal death)
the elimination of massive cell death is part of normal d………. and m………
after maturity, the apoptotic mechanisms become d……
the visual cortex is actually thicker in blind people due to a lack of v….. s……
-it cannot prune out ineffective neurons
the elimination of massive cell death is part of normal development and maturation
after maturity, the apoptotic mechanisms become dormant
the visual cortex is actually thicker in blind people due to a lack of visual stimuli
-it cannot prune out ineffective neurons
(the vulnerable developing brain)
early stages of brain development are critical for normal d………. Later in life
a mutation on one gene can lead to many d……
chemical distortions in the brain during early development can cause significant i……… and d………… problems
normal development later in life
can lead to many defects
impairment and developmental problems
(fetal alcohol syndrome)
a condition that children are born with if the mother…?
marked by the following:
- hyper…….. and i………..
- difficulty maintaining..?
- varying degrees of mental r……….
- motor problems and h…. d……
- facial a…………
drinks heavily during pregnancy
- hyperactivity and impulsiveness
- difficulty maintaining attention
- varying degrees of mental retardation
- motor problems and heart defects
- facial abnormalities
(fetal alcohol syndrome coninued)
the dendrites of children born with fetal alcohol syndrome are…?
exposure to alcohol in the fetus brain suppresses glutamate and enhances the release of GABA
many neurons consequently receive less excitation and exposurre too neurotrophins than usual and undergo…? A……..
short with few branches
apoptosis
(differentiation of the cortex)
neurons in different parts of the brain differ from one another in their s…. and c……. components
- immature neurons transplanted to a developing part of the cortex develop the properties of the new L…….
- neurons transplanted at a later stage of development develop some new properties but retain some o.. P………
shape and chemical components
new location
retain some old properties
-the ferret experiment
(fine-tuning by experience)
the brain has some ability to reorganize itself in response to e………
- a…. and d…….. continue to modify their structure and connections throughout the lifetime
- d…….. continually grow new spines
the gain and loss of spines indicates new connections, which relates to l…….
experience
- axons and dendrites
- dendrites
- learning
(experience and dendritic branching)
rats raised in an enriched environment develop a thicker c….., increased d…….. branching and improved l…….
measurable expansion of neurons has also been shown in humans as a function of p……. a…….
as old neurons die by apoptosis and new ones form to take their place, there is improved l……. and m…..
thicker cortex, increased dendritic branching and improved learning
physical activity
learning and memory
(experience and dendritic branching continued)
it was once believed that teaching a child a difficult concept (greek, advanced math, ect.) would enhance i……….. in other areas
-this concept is known as “far transfer”
evidence shows that skills associated with the practiced transfer, but not other skills
-the brain cannot be “exerised” like a m…..
intelligence
muscle
(effects of special experiences)
blind people improve their attention to touch and sound, based on practice
-touch information activated this occipital cortex area, which ordinarily is devoted to v….. alone
the occipital lobe normally dedicated to processing visual information adapts to also process tactile and v….. information
vision
verbal
(brain adaptations)
people who are deaf from an early age become more responsive to t…. and v…..
t…. and v….. come to activate what would be the a……. cortex in deaf people
touch and vision
auditory
(music training)
MRI studies reveal the following:
- the t……. lobe of professional musicians in the right hemisphere is 30% larger than non-musicians
- thicker gray matter in the part of the brain responsible for h… control and v….. of professional keyboard players
- results suggest that practicing a skill reorganizes the brain to maximize performance of that skill
temporal
hand control and vision
(special training in adulthood)
adult experiences can also modify b…. a……
however, research is needed to determine whether the effects are strong enough to be observed with … or similar technology
brain anatomy
MRI
(when brain organization goes too far)
focal hand dystonia or “musicians cramp” refers to a condition where r…………. Of the brain goes too far
- the fingers of musicians who practice extensively become c….., f…… easily, an make i………. m……..
- this condition is a result of extensive reorganization of the s…… thalamus and cortex so that touch receptors to one finger overlap those of another
the reorganization of the brain goes too far
become clumsy, fatigue easily, and make involuntary movements
sensory thalamus
(brain development and behavioral development continued)
adolescents tend to be more i…….. than adults
-i…….. can be a problem when it leads to drinking, risky driving, se, etc.
adolescents tend to “discount the future”
impulsive
impulsivity
(brain development in adolescents)
adolescents aren’t equally impulsive in all situations
-peers, amount of time to make decisions, etc. affect their decisions
the p……… cortex of adolescents is relatively inactive in certain situations, but this may not be the cause of impulsivity
prefrontal cortex
(brain development and old age)
some neurons lose their synapses, and the remaining synapses change more slowly than before in response to e……….
brain structures begin to lose v…..
research underestimates older people:
- people vary in respect to i……….. decline
- older people have greater base of knowledge and experience, and many find ways to c……… for loses
experiences
volume
intellectual decline
compensate
