Neurulation and Neural Tube Quiz

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Questions and Answers

Which of the following brain subdivisions is primarily responsible for sensory and motor relay functions?

Metencephalon

Diencephalon (correct)

Mesencephalon

Telencephalon

What is the consequence of holoprosencephaly in terms of brain development?

Incomplete development of the medulla oblongata

Excessive formation of brain hemispheres

Abnormal enlargement of the midbrain

Failure of the forebrain to split into hemispheres (correct)

Which compound is identified as a specific inhibitor of the Sonic Hedgehog pathway, leading to holoprosencephaly?

Teratogen

Cyclopamine (correct)

Lithium

Thalidomide

Which characteristic defines cerebellar hypoplasia?

Incomplete development of the cerebellum Signup and view all the answers

What type of brain structure correlates with auditory and visual reflexes?

Mesencephalon Signup and view all the answers

Exposure to which of the following viruses is known to cause cerebellar hypoplasia?

Feline panleukopenia virus Signup and view all the answers

What is the result of the neural canal narrowing and then reopening during brain development?

Release of pressure leading to further brain enlargement Signup and view all the answers

Which brain subdivision is primarily involved in motor coordination?

Metencephalon Signup and view all the answers

What role does the notochord play in the development of the nervous system?

It induces ectodermal cells to differentiate into neural tissue. Signup and view all the answers

During which process is the neural tube formed?

Neurulation Signup and view all the answers

Which of the following statements about the closure of the neural tube is correct?

The closure begins in the cervical area and progresses towards both ends. Signup and view all the answers

What is a likely consequence of failures in neural tube closure?

Development of conditions like spina bifida Signup and view all the answers

How do the maturity levels of newborns differ among species such as calves, puppies, and humans?

Calves are born ready to run, while puppies and humans require time to develop. Signup and view all the answers

What is the initial response of ectodermal cells during induction caused by the notochord?

They become neural tissues and thicken to form the neural plate. Signup and view all the answers

Which factor is essential for the process of induction in embryonic development?

Tissue capable of producing a stimulus and a responsive tissue Signup and view all the answers

What is a role of the ectoderm in the development of the neural groove?

It elevates to form the neural folds. Signup and view all the answers

Which defect results from an incomplete closure of the cranial neuropore?

Encephalocele Signup and view all the answers

What condition results from complete failure of the cephalic neural tube to close?

Anencephaly Signup and view all the answers

What is the main consequence of the defective or absent vertebral arch in spina bifida?

Incomplete dorsal growth around spinal cord Signup and view all the answers

What role do cadherins play in the development of the neural tube?

Mediating separation of neuroectoderm from surface ectoderm Signup and view all the answers

Which gradient is crucial in influencing Hox gene expression along the cranial/caudal axis?

Retinoic acid gradient Signup and view all the answers

Which statement accurately describes the relationship between Hox gene expression and retinoic acid?

Hox gene expression patterns are induced by retinoic acid exposure. Signup and view all the answers

What type of neural tube closure defect is specifically characterized by spinal cord abnormality?

Spina bifida Signup and view all the answers

What is the consequence of the caudal expression of retinoic acid synthesizing enzymes?

Establishment of a retinoic acid gradient Signup and view all the answers

Study Notes

Neurulation and the Neural Tube

Neurulation is the early development of the nervous system, including the induction of the neural plate and neural tube closure.
The nervous system is one of the first organ systems to develop, and one of the last to complete its maturation.
The neural plate, a thickened midline strip of ectodermal cells, is destined to become the central nervous system.
Induction is when the differentiation of one tissue is controlled by a second tissue in close contact.
The notochord and prechordal plate induce ectodermal cells to become neural tissue.
The ectoderm thickens over the notochord, forming the neural plate, which then folds to form a neural groove.
The neural folds meet and fuse, forming the hollow neural tube. This process begins in the cervical area and proceeds rostrally and caudally.
Defects in neural tube closure can result in developmental anomalies, including spina bifida, encephalocele, exencephaly, or anencephaly.
Encephalocele is incomplete closure of the cranial neuropore, resulting in brain protrusion.
Exencephaly is complete failure of the cephalic neural tube to close, resulting in brain degeneration.
Spina bifida is a defective or absent vertebral arch, often with some spinal cord abnormality.

Induction

Many tissues develop as a result of interactions between two or more groups of cells with separate origins.
Induction requires a tissue capable of producing a stimulus (often a chemical) and a tissue capable of responding to it.
No tissue can form an organ by itself; it must interact with other tissues, typically through induction.

Neural Tube Closure

The neuropore closure happens simultaneously along the neural tube
The rostral and caudal ends of the neural tube remain open during temporarily and are called Neuropores

Cell Adhesion Molecules

Expression of distinct cell adhesion molecules (cadherins) by the neural tube is crucial in separating the neuroectoderm from the surface ectoderm.
N-cadherin is expressed by the neuroectoderm, and E-cadherin, is expressed on the surface ectoderm.
These differences in cell adhesion molecule expression prevent these two ectodermal derivatives from sticking together.

Pattern Formation

Complex patterns of gene expression, particularly those of Hox genes, are established along the cranial/caudal axis of the developing neural tube.
These gene expression patterns specify the spatial identity of the neural tube along the cranial/caudal axis.
Sonic hedgehog (Shh) protein is a growth factor; it signals ventral identity.
Tgf-beta family proteins, such as BMPs, signal dorsal identity.
Retinoic acid gradients influence Hox gene expression.

Histogenesis in the Developing Neural Tube

Histogenesis is the formation of different tissues from undifferentiated cells.
Early neural tube consists of primitive neuroectodermal cells arranged in a pseudostratified columnar layer.
Neuroectodermal cells are multipotent, giving rise to neurons, macroglia (astrocytes and oligodendrocytes), and ependyma.

Early Brain Development

The rostral end of the neural tube expands rapidly to form the brain.
Expansion primarily results from increased lumen size, driven by fluid pressure changes.
Five major subdivisions of the brain develop from three original dilations.
The general organizational plan in the spinal cord (alar versus basal) is also followed in the brain, with variations in growth and cell migration.

Ventricles

The original neural tube lumen expands into the ventricular system of the brain.
The ventricular system is continuous with the central canal of the spinal cord and the subarachnoid space of the meninges.
Choroid plexus within these spaces produces cerebrospinal fluid (CSF), which constantly circulates and is reabsorbed.
Improper reabsorption/production of CSF leads to hydrocephalus.

Holoprosencephaly

Failure of the rostral forebrain to split into two hemispheres.
Associated with cyclopia.
Can be induced by Cyclopamine

Cerebellar Hypoplasia

The cerebellum's development is incomplete.

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Description

Test your knowledge on the process of neurulation and the formation of the neural tube. This quiz covers the early stages of nervous system development, including the induction of neural tissue and potential developmental anomalies associated with neural tube closure defects. Prepare to explore the intricacies of embryonic development!