CNS Development Overview

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Questions and Answers

Which of these cell types can differentiate into any cell type in the body?

Unipotent

Pluripotent

Multipotent

Totipotent (correct)

At what developmental stage are cells considered to be totipotent?

Blastula

Morula (correct)

Neural tube

Gastrula

What is the key difference between pluripotent and multipotent stem cells?

Pluripotent cells can differentiate into many, but not all, cell types, while multipotent cells can only differentiate into a few cell types within a specific lineage. (correct)

Pluripotent cells are responsible for the development of the nervous system, while multipotent cells are responsible for the development of other organ systems.

Pluripotent cells are only found in the early embryo, while multipotent cells are found throughout the body.

Pluripotent cells can only differentiate into one specific cell type, while multipotent cells can differentiate into multiple cell types.

Which of the following is an example of a tissue type that can be derived from multipotent stem cells in the neural crest?

Epinephrine-producing cells of the adrenal medulla (C) Signup and view all the answers

What is the significance of the neural crest?

It gives rise to a diverse range of cell types, including neurons, glia, and pigment cells. (B) Signup and view all the answers

What type of stem cell is responsible for the development of the neural tube?

Multipotent (B) Signup and view all the answers

If a totipotent embryonic cell is removed and transplanted, what is likely to happen?

It will form a new embryo, leading to the development of identical twins. (B) Signup and view all the answers

What is the main function of pluripotent stem cells?

To form the germ layers, ectoderm, mesoderm, and endoderm. (D) Signup and view all the answers

Which of the following statements accurately describes the process of neural proliferation?

Neural proliferation occurs primarily in the ventricular zone of the neural tube. (A) Signup and view all the answers

Which of the following is NOT a type of neuronal migration?

Somal Translocation (C) Signup and view all the answers

Which of the following statements is true about cell adhesion molecules (CAMs)?

They play a role in migration, recognition, and adhesion. (D) Signup and view all the answers

Which of the following conditions results from a disruption in the migration of neurons?

All of the Above (D) Signup and view all the answers

What are the two major hypotheses explaining how growth cones find their target?

Chemoaffinity Hypothesis and Topographic Gradient Hypothesis (D) Signup and view all the answers

What is the primary function of filopodia on a growing axon?

They extend and retract to sense and respond to their environment. (A) Signup and view all the answers

Which of the following statements correctly describes the formation of a gap junction?

Two adjoining connexons form a gap junction. (C) Signup and view all the answers

Which of the following statements is NOT a common misconception about neural proliferation?

Neural proliferation is regulated by chemical signals. (C) Signup and view all the answers

In Sperry's study, how does the evidence support the Chemoaffinity Hypothesis?

The connections between the retina and the optic tectum are maintained despite rotation of the eye. (C) Signup and view all the answers

What is the main issue with the Chemoaffinity Hypothesis, as described in the provided text?

Experiments involving transplanted targets contradict the hypothesis. (B) Signup and view all the answers

What is the role of fasciculation in axonal growth?

Fasciculation allows growth cones to follow existing axons, ensuring a directed path to the target. (A) Signup and view all the answers

Which of the following is NOT a component of the Topographic Gradient Hypothesis?

The hypothesis primarily focuses on the role of cell adhesion molecules in axon guidance. (C) Signup and view all the answers

How do the findings of in vitro studies regarding synapse formation support the role of astrocytes?

Neurons cultured with astrocytes form a significantly higher number of synapses compared to those without. (C) Signup and view all the answers

What is the main difference between the Chemoaffinity Hypothesis and the Topographic Gradient Hypothesis?

The Topographic Gradient Hypothesis focuses on the role of chemical gradients, while the Chemoaffinity Hypothesis emphasizes specific chemical labels. (A) Signup and view all the answers

What is the main implication of the revised Chemoaffinity Hypothesis?

Guidance cues for axonal growth involve both chemical trails and the guidance of pioneer growth cones. (A) Signup and view all the answers

What is the best interpretation of the statement "Both!" in the text?

Both the Chemoaffinity and Topographic Gradient hypotheses are correct and contribute to axonal growth. (A) Signup and view all the answers

Which of the following is NOT a key characteristic of the neural crest?

It is only found in mammals. (A) Signup and view all the answers

Which of these statements accurately describes the role of gastrulation in embryonic development?

Gastrulation results in three germ layers: ectoderm, mesoderm, and endoderm, which give rise to distinct tissues and organs. (B) Signup and view all the answers

Which of the listed sources highlights the use of fluorescence microscopy in studying zebrafish embryos?

Zeiss Microscopy (2014).Zebrafish embryo, multiview light-sheet fluorescence microscopy.Flickr.https://www.flickr.com/photos/zeissmicro/12206703494 (C) Signup and view all the answers

Based on the provided context, what is the focus of the TV series episode 'The Secret of the Wild Child (S21, E12)'?

The series explores the developmental challenges faced by children raised in isolation, focusing on the case of Genie. (A) Signup and view all the answers

The sources listed primarily focus on which aspect of developmental biology?

The cellular and molecular processes involved in the formation of tissues and organs. (A) Signup and view all the answers

What is the primary function of neurotrophins in relation to neurons?

Promote neuronal growth and survival (C) Signup and view all the answers

Which process represents a 'clean' form of cell death?

Apoptosis (D) Signup and view all the answers

What causes the death of surplus neurons during development?

Genetic programming and competition for neurotrophins (B) Signup and view all the answers

What is a characteristic of developing neurons?

They tend to make many connections, some of which are not essential. (D) Signup and view all the answers

Which neurotrophin was the first to be isolated?

Nerve growth factor (NGF) (B) Signup and view all the answers

What is often the result of neuronal cell death in terms of synaptic accuracy?

Increases the overall accuracy of synaptic connections (B) Signup and view all the answers

What is the term for passive cell death?

Necrosis (B) Signup and view all the answers

What role do neurotrophins play in axon guidance?

They serve as guidance molecules for axons. (A) Signup and view all the answers

What is the name of the process by which cells differentiate, migrate, and establish functional connections with other cells?

Differentiation and Migration (D) Signup and view all the answers

Which of the following is NOT a stage of embryonic development of the Nervous System?

Synaptic Pruning (A) Signup and view all the answers

What is the name of the structure that forms from the neural groove during embryonic development?

Neural Tube (C) Signup and view all the answers

Which of the following is NOT a characteristic of pre-natal development of the CNS?

Significant pruning of synapses (A) Signup and view all the answers

Which of the following is TRUE about the development of the CNS?

The CNS remains plastic throughout life, constantly adapting to experiences. (C) Signup and view all the answers

What is a plausible, though not definite, reason that the case of 'Genie' is often incompletely described, even in accounts of children with similar histories?

Genie's story is very complex and nuanced, and focusing on only certain aspects can create a misleading picture. (C) Signup and view all the answers

What is the role of the mesoderm in early CNS development?

The mesoderm induces the formation of the neural plate. (B) Signup and view all the answers

Which of the following best describes the relationship between genes and environment in CNS development?

Genes and environment interact continually throughout life, impacting CNS development and function. (A) Signup and view all the answers

Study Notes

Development of the Central Nervous System

The central nervous system (CNS) continues to develop throughout life, not just during prenatal and childhood stages.
Prenatal development, childhood development, and adulthood are key topics of CNS development.
Disorders of neurodevelopment, such as Autism Spectrum Disorder and Williams Syndrome, are also addressed.

Historical View of CNS Development

Historically, the CNS was viewed as a stable, fixed organ by adulthood.
However, modern understanding encompasses brain plasticity, demonstrating continuous changes throughout life.

Current, Comprehensive View of CNS Development

The development of the CNS involves an ongoing interaction between genes and the environment, from prenatal (in utero) stages, through childhood, to adulthood.

Genes and Environment: The Case of "Genie"

The case of "Genie" highlights the critical role of environmental experience in CNS development, although stories about such cases often don't show the full picture.

Prenatal Development of the CNS

Gametogenesis (through meiosis) involves the creation of egg and sperm, leading to fertilization, which produces a zygote.
Mitosis occurs after fertilization, producing multiple cells.

After Formation

Once cells develop, they must differentiate into their specific cell types (e.g., muscle, liver, neurons, glia).
They need to migrate to their appropriate locations.
Cells must establish functional connections with other cells.

Embryonic Development of the Nervous System

Key stages in embryonic nervous system development: neural plate induction, neural proliferation, migration and aggregation, axon growth and synapse formation, and neuron death and synapse rearrangement.

Induction of the Neural Plate

Induction of the neural plate originates from ectoderm cells, leading to the creation of the neural groove. Then the neural groove folds in to create a neural tube.
This occurs through chemical signals originating from adjacent mesoderm cells.
The neural tube develops specific components: a central canal and neural crest.

Neural Proliferation

During neural tube development (around 40 days post-fertilization), ectodermal tissue differentiates into three vesicles.
Neural proliferation peaks shortly after neural tube closure.
Chemical signals influence and regulate the process of neural tube development.
Development proceeds in an anterior-to-posterior manner.

Migration and Aggregation

Migration involves the movement of newly formed cells to their correct positions, often guided by chemical signals.
Types of migrations include: Radial, Tangential, and Multipolar migration.
Aggregation involves cell clustering and connections.

Cell Adhesion Molecules

Cell adhesion molecules (CAMs) are crucial components in the interactions of aggregating cells and promoting recognition
Gap junctions facilitate communication and connections between cells.

Disorders of Neuron Migration

Kallmann syndrome is characterized by abnormal genitals and a dysfunctional sense of smell.
Lissencephaly results from cytoskeleton defects obstructing neuronal migration.
Other disorders (Schizophrenia, Bipolar Disorder, Autism Spectrum Disorders, Dyslexia) may also be linked to neuron migration issues.

Axon Growth and Synapse Formation

Axon growth originates from the axon growth cone extending and retracting filopodia.

How Growth Cones Find Their Target

Chemoaffinity Hypothesis: suggests target-specific chemical labels guide axon growth.
Topographic Gradient Hypothesis: proposes intersecting gradients (up-down and left-right) of chemicals guide axons.

Evidence for the Chemoaffinity Hypothesis

Sperry's study of eye rotation and regeneration in frogs demonstrates the importance of specific chemical labels in axon guidance.

Evidence Contradicting the Chemoaffinity Hypothesis

In cases where transplanted targets receive incorrect innervation, the chemoaffinity hypothesis is challenged.
The route to the target is often circuitous, not linear.

Revised Chemoaffinity Hypothesis

Pioneer growth cones initially follow chemical gradients.
Subsequent growth cones follow pioneer growth cones via fasciculation (axons following previous axons).

Topographic Gradient Hypothesis

Intersecting chemical gradients guide axonal growth between different regions.
The maintenance of topographic integrity is vital for correct functionality of neural structures like the optic tectum, and is supported by the presence and differentiation of ephrin molecules.

Synapse Formation

Requires neuron-neuron communication.
Glia cells (astrocytes) support the development of synapses.
In vitro and in vivo studies highlight the role of astrocytes in promoting and inhibiting signals.

Functions of Neuronal Cell Death

Overproduction of neurons, followed by a subset dying.
Death of neurons that make incorrect connections improves the accuracy of synaptic connections.
New neurons creating more focused synapses.

Processes of Cell Death

Apoptosis is an active, regulated process, removing damaged or unwanted cells.
Necrosis is a passive, uncontrolled process.

What Causes Neurons to Die

Genetic programming or preprogrammed cell death accounts for the death of some neurons.
Competition for target-supplied neurotrophins is a major cause of neuronal death.
The availability of neurotrophic factors regulates neural growth and survival.

Neurotrophins

Types of neurotrophins include NGF, BDNF, GDNF, NT-3, NT-4/5, CNTF, and bFGF.
These factors affect neuron development and survival in several ways.

Functions of Neurotrophins

Promotion of neural growth and survival.
Acting as axon guidance molecules.
Assisting in synaptogenesis (the formation of synapses).
Trigger apoptosis when absent; therefore, survival and development are dependent upon their presence.

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Description

Explore the intricate development of the central nervous system (CNS) from prenatal stages to adulthood. This quiz covers key concepts of neurodevelopment, including the impacts of genetics and environment, and discusses disorders such as Autism Spectrum Disorder. Understand how historical views have evolved to recognize brain plasticity throughout life.