Neurodevelopment Flashcards

Question

Cell Death

Answer 1

If you don’t use it, you lose it;

Answer 2

Neuronal networks become more efficient in their communication; Sign of neurodevelopmental maturity; Occurs well into adulthood;

Answer 3

- SVZ contains a primitive map of the cerebral cortex; | - Cells formed in certain regions of the SVZ migrate to certain cortical locations.

Answer 4

- Form a path that extends from the SVZ to the surface of the cortex; - Undifferentiated progenitor cells follow this path. Cortical layers form from inside out. The most inner layer (VI) are first to form. Q: How do neurons know when to stop? (i.e. cortical thickness)

Answer 5

``` Intercellular signals (i.e. between cells) progressively restrict the choice of traits a cell can express. Therefore, the emergence of a cell type is a combination of genetic instructions, timing and signals from neighboring cells in the local environment. ```

Answer 6

1. Dendritestoprovidesurfacearea for synapse formation: - Branching of dendrites (arborization); - Growth of dendritic spines (μm.day-1). 2. Axon extending to appropriate target to initiate synapse formation - Occurs very rapidly (mm.day-1); - Various molecules attract or repel axon tip, thus guiding it through a very complex terrain.

Answer 7

Santiago Ramón y Cajal defined growing axons as growth cones.

Answer 8

Growth cones extend shoots called filopod (e.g. fingers on a hand); When filopod reaches an appropriate target, the others follow.

Answer 9

1. Cell-adhesion Molecules (CAMs) Secreted from cells or lie on cell surface. 2. Tropic Molecules Secreted from target cells; Carry “come here” or “go away” message; Netrin (L. to guide) is the only known group.

Answer 10

Human brain contains about 1014 synapses; - The amount and array of synaptic connections is thought to be guided mostly by environmental cues and signals; - At 7th gestational months, these connections are rather simple; - At birth, the number of synapses increases dramatically; - By 2 – 4 months, the number of synapses in the visual cortex doubles, and continues to increase for years.

Answer 11

The brain uses apoptosis as a method of pruning - Genetics signals, experience, hormones, stress, etc. are all factors that can initiate apoptosis; - ~42% of all synapses in human cortex are lost. Neural Darwinism - Competition drives neuronal loss; - Environmental pressure leads to competition amongst neurons.

Answer 12

is a neurotrophic factor produced by cells that regulate neuronal survival; - Therefore, neurons that are deprived of NGF will undergo apoptosis; - Those neurons who make connections early on will be nourished with NGF and other growth factors. Generally, the cortex continues to thin from ages 5 to 20 The exception to this is in language centers - Unique role of language processing and nature of language-learning processes makes this area an exception to this rule.

Answer 13

Frontal lobe is the last brain region to mature - Pruning occurs into the 20’s Process of myelination can be used as an index of neuronal maturity. Early-myelinating areas control simple movement, while late-myelinating areas control highest mental function.

Answer 14

Donald Hebb (1947) - Took some laboratory rats home and let them grow up in his kitchen; - Control group stayed at McGill University; - The ‘home’ rats had many more experiences then the ‘cage’ rats; - On subsequent intelligence tests, the home rats outperformed the cage rats; - Hebb concluded that experience must influence intelligence in some way; - Hebb’s experiment lead to the development of Sesame Street which aimed to offer enrichment for children.

Answer 15

Stimulation is extremely important during development and cortical organization - Tactile stimulation has been shown to increase the growth rate of pre-mature babies in an incubator; - Brushing infant rats for 15 minutes 3 times daily speeds up growth and development; - Tactile stimulation of infants is important for forming bond with caregiver; - Experience changes structure of neurons, especially cortical neurons; - Processing of sensory information increases number of synapses and astrocytes.

Answer 16

Donald Hebb (1951), Sensory Deprivation Studies - Placed Scottish terrier in the dark with as little stimulation as possible and compared them to ‘normal’ dogs; - Later in life, deprived dogs didn’t pay attention to other dogs or humans; - Lost sensation of pain; - Performed very poorly on intelligence test; - Depriving young animals of visual input or maternal contact has devastating; consequences on behavioral development (and presumably brain development).

Answer 17

Austin Riesen (1982) - Extensively studied animals raised in the dark; - Atrophy of dendrites in visual cortex, which is the opposite of what happened to the enriched rats; - Eye still worked, but functionally blind. Harry Harlow (1950’s) - Monkeys raised with no maternal/paternal contact showed abnormal intellectual and social behaviors in adulthood; - There are a number of hormonal and neurobiological abnormalities among motherless monkeys. Romanian Orphans (1970’s) - Birth control & abortions were outlawed; - Fed and clothed, but virtually no environmental stimulation; - Motor and cognitive impairments; - Age of adoption dictated extent of recovery.