Podcast
Questions and Answers
What are the three phases of early neurodevelopment?
What are the three phases of early neurodevelopment?
- Induction of the neural plate
- Neural proliferation
- Migration and aggregation
What are the four phases of brain growth in ASD?
What are the four phases of brain growth in ASD?
Which two primary brain regions are known to experience adult neurogenesis?
Which two primary brain regions are known to experience adult neurogenesis?
- Olfactory bulb
- Dentate gyrus
What are the two processes of cell death?
What are the two processes of cell death?
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Name the three embryonic cell layers and their corresponding tissues.
Name the three embryonic cell layers and their corresponding tissues.
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Which of the following is NOT a neurotrophin?
Which of the following is NOT a neurotrophin?
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The chemoaffinity hypothesis states that growing axons are attracted to the correct targets by different chemicals released by the target sites.
The chemoaffinity hypothesis states that growing axons are attracted to the correct targets by different chemicals released by the target sites.
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What are the five key postnatal developmental events?
What are the five key postnatal developmental events?
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What is the difference between a critical period and a sensitive period?
What is the difference between a critical period and a sensitive period?
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What is the difference between permissive and instructive experience?
What is the difference between permissive and instructive experience?
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What is the function of the prefrontal cortex?
What is the function of the prefrontal cortex?
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What is the name of the test used to assess frontal lobe function in adults?
What is the name of the test used to assess frontal lobe function in adults?
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What are the two types of migration that occur during neurodevelopment?
What are the two types of migration that occur during neurodevelopment?
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What are the two mechanisms by which neurons migrate?
What are the two mechanisms by which neurons migrate?
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What are the three factors that mediate aggregation?
What are the three factors that mediate aggregation?
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What are the two types of cell death?
What are the two types of cell death?
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What are the three reasons why neurons die?
What are the three reasons why neurons die?
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What are two examples of atypical neurodevelopment?
What are two examples of atypical neurodevelopment?
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Study Notes
Early Neurodevelopment
- Cells must differentiate into specialized types (muscle, liver, neurons, glia), migrate to correct locations, and establish connections with other cells.
- The case of Genie highlights the crucial role of experience in neurodevelopment.
- A zygote (fertilized egg) undergoes rapid division, forming an embryo.
Five Phases of Early Neurodevelopment
- Neural plate formation
- Neural proliferation (rapid neuron increase)
- Migration and aggregation (neurons move to correct positions and connect)
- Axon growth and synapse formation (branching and connection formation)
- Neuron death and synapse rearrangement (pruning of connections for efficiency)
Stem Cells
- Stem cells are undifferentiated cells with the potential to become many different cell types.
- Totipotent stem cells (early embryonic) can develop into any cell type.
- Pluripotent stem cells can develop into most cell types.
- Multipotent stem cells can develop into specific cell types within a class.
- Unipotent stem cells differentiate into only one specific cell type.
Cell Layers and Neural Structures
- Embryonic development involves three germ cell layers: endoderm (gut lining), mesoderm (muscles, connective tissue), and ectoderm (skin, nervous system).
- The neural plate arises from the ectoderm, forming the neural tube (brain and spinal cord).
- The neural crest gives rise to neurons and glia of the peripheral nervous system.
Neural Proliferation, Migration, and Aggregation
- Neural proliferation is the rapid increase in neurons, peaking after the neural tube closes.
- Radial glial cells guide neuron migration from the ventricular zone to their final location.
- Radial migration occurs in a straight line, while tangential migration is perpendicular.
- Somal translocation and glial-mediated migration are mechanisms of neuron movement.
- Aggregation involves the alignment of neurons, facilitated by CAMs, gap junctions, and glial-neuron interactions.
Axon Growth and Synaptogenesis
- Axon growth begins with growth cones, guided by chemoaffinity and topographic gradients.
- Sperry's study on eye rotation showed the importance of chemoaffinity for specific neuron connections.
- Synaptogenesis (synapse formation) is dependent on neuron-neuron and glial cell interaction.
Neuron Death and Neurotrophins
- Neuronal cell death is a crucial part of development, removing incorrect connections. Apoptosis is active and "clean" cell death—necrosis is passive and "dirty".
- Neurotrophins (e.g., NGF, BDNF, GDNF) are vital for neuron growth, survival, and synaptogenesis. Their absence triggers apoptosis.
Postnatal Brain Development
- Postnatal brain development involves continued synaptogenesis, myelination, dendritic branching and regressive changes (synaptic pruning).
- The prefrontal cortex (PFC) develops slowly, contributing to the slow maturation of executive functions.
Experience and Neurogenesis
- Experience significantly influences neurodevelopment (use-it-or-lose-it).
- Critical and sensitive periods during development show experience-dependent neuroplasticity.
- Animal studies demonstrate experience-dependent changes in brain structure and function (ferrets, barn owls, mice). Human studies show enrichment effects on brain areas related to activity (auditory cortex, hippocampus).
Adolescent Brain Development
- Adolescence is a period of significant brain reorganization, involving axonal and dendritic pruning and myelination.
- Functional development in the prefrontal cortex continues into adolescence. Correlates in behavior include enhanced sensitivity to dopamine/oxytocin, novelty seeking, risk-taking.
Adult Neurogenesis
- Adult neurogenesis occurs in distinct brain regions (olfactory bulb and dentate gyrus).
- The olfactory bulb maintains old and introduces new interneurons/neurons.
- The dentate gyrus produces new granule cells for learning and memory.
- Intrinsic (hormones, injury) and extrinsic (enriched environment, exercise) factors contribute to adult neurogenesis.
Atypical Neurodevelopment: ASD
- Autism Spectrum Disorder (ASD) involves difficulties with social interaction and restricted behaviors, often with increased risk of intellectual/learning disability and epilepsy.
- ASD is now diagnosed in more individuals due to changed diagnostic criteria and improved awareness and diagnosis.
- Genetic factors are key to ASD, influencing early or mid-development. Environmental factors also play a role.
- Many genes are impacted in the brains of ASD patients and there are patterns of hyper-connectivity (increased neural fluctuations) and underconnectivity (reduced neural density in the frontal lobe). Oxytocin may be a useful intervention in certain instances and further study is needed.
Atypical Neurodevelopment: Williams Syndrome
- Williams syndrome involves distinct characteristics, notably social behaviour (sociable, empathetic), language ability, musical talent, and an impairment in spatial cognition.
- Chromosomal deletion, specifically on chromosome 7, is associated with the disorder.
- There are anatomical anomalies that may affect specific skill domains.
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Description
Explore the fascinating journey of early neurodevelopment, including the five critical phases from neural plate formation to synapse rearrangement. This quiz delves into the role of stem cells in differentiation and their types, such as totipotent, pluripotent, and multipotent stem cells. Test your understanding of how these processes shape the development of specialized cell types.
