Development and Anomalies of Development of the CNS

Question 1

Why are ventral and anterior used interchangeably normally but not in the brain?

Answer 1

In general usage, ventral and anterior can mean the same, but in the brain, their meanings differ due to the brain’s orientation

Question 2

What do ‘rostral’ and ‘caudal’ refer to?

Answer 2

‘Rostral’ refers to the front or nose end, while ‘caudal’ refers to the tail end.

Question 3

Why is studying the CNS useful?

Answer 3

It helps to understand neurological and psychiatric diseases, their causes, prevention, treatment, and repair.

Question 4

What is neurogenesis?

Answer 4

Neurogenesis is the process of producing new neurons.

Question 5

What is neuroplasticity?

Answer 5

Neuroplasticity is the ability to take existing neurons and get them to regrow and reform connections.

Question 6

What is grey matter?

Answer 6

Grey matter consists of neuronal cell bodies.

Question 7

What is white matter?

Answer 7

White matter is made up of myelinated axons.

Question 8

What are the two phases of brain development?

Answer 8

The two phases are pre-natal and post-natal.

Question 9

When are the first neurons born and why is this important?

Answer 9

The first neurons are born 22-26 days after fertilization, which is crucial as some mothers may be unaware of their pregnancy and affect neuron production.

Question 10

When is the majority of proliferation complete?

Answer 10

The majority of proliferation is complete 12 months post-natal.

Question 11

What is myelination and when is it complete?

Answer 11

Myelination is an important process for the efficient function of neurons, and it is only 50% complete by 18 months post-natal.

Question 12

When does the number of synapses increase?

Answer 12

The number of synapses increases during the first three years post-natal.

Question 13

What can lead to fewer synapses being made?

Answer 13

Poor nutrition, social interaction, and parental interaction before the age of three can lead to fewer synaptic connections.

Question 14

When does gross brain structure stop changing?

Answer 14

Gross brain structure stops changing around 20 years old, but dynamic processes continue throughout life.

Question 15

What is gastrulation?

Answer 15

Gastrulation is the process where the embryo transforms from a bilaminar structure into a trilaminar structure.

Question 16

What are the three germ layers formed by gastrulation?

Answer 16

The three germ layers are endoderm, mesoderm, and ectoderm.

Question 17

Which layer is the nervous system developed from?

Answer 17

The nervous system is developed from the ectoderm.

Question 18

What is neural induction?

Answer 18

Neural induction is when the notochord induces the overlying ectoderm to become the neural plate.

Question 19

What do the neural tube and neural crest form respectively?

Answer 19

The neural tube forms the CNS (including oligodendrocytes), while the neural crest forms neurons with cell bodies in the peripheral system and Schwann cells.

Question 20

What happens during embryonic folding?

Answer 20

During embryonic folding, the middle part of the embryo closes first, followed by the anterior neuropore and then the posterior neuropore.

Question 21

What can cause interference in neural tube closure?

Answer 21

Lack of massive cell division, dependent on folic acid, and gene defects affecting cell-cell interaction can cause interference.

Question 22

How does folic acid deficiency cause defects in neural closure?

Answer 22

Folic acid is needed for DNA synthesis, which drives the massive cell proliferation required for proper neural tube closure.

Question 23

What are the three vesicles in the rostral neural tube?

Answer 23

The three vesicles are the forebrain, midbrain, and hindbrain.

Question 24

What are anteriorising signals?

Answer 24

Anteriorising signals are molecules that help determine whether neurons are in the anterior part of the brain, such as Dickkopf and noggin.

Question 25

What is Sonic hedgehog (Shh) signaling?

Answer 25

Sonic hedgehog (Shh) signaling is responsible for the expression of neurons in the ventral aspect of the brain.

Question 26

What happens if there is an interruption in the processes determining neuron location?

Answer 26

An interruption can result in neurons ending up in the wrong place, preventing the formation of nuclei.

Question 27

How is the organization of the cortex different from subcortical structures?

Answer 27

The cortex has a more advanced organization in layers compared to the subcortical structures.

Question 28

What is the difference in organization between the sub-cortex and cortex?

Answer 28

The subcortical structures have a simpler organization, while the cortex is more advanced and organized in layers.

Question 29

Why does the cortex have different layers?

Answer 29

The cortex has identifiable layers with different densities and types of neurons due to a process known as cortical layering.

Question 30

How many layers are in the human neocortex?

Answer 30

There are 6 layers in the human neocortex, with layer 6 being the innermost.

Question 31

What differs in each layer of the cortex?

Answer 31

Each layer has different densities of neurons and varying sizes of cell bodies.

Question 32

What is layer 6 adjacent to in a fully formed brain versus early stages?

Answer 32

In a fully formed brain, layer 6 is adjacent to the white matter; in early stages, it is adjacent to the ventricles.

Question 33

Where do the cells in layers 1-6 originate from?

Answer 33

The cells in layers 1-6 originate from a strip of cells adjacent to the fluid-filled vesicle in the early brain.

Question 34

What are the 3 stages in the process of cortical layering?

Answer 34

1. Proliferation: High rate of neuroblast production. 2. Migration: Neurons move to their designated layers. 3. Differentiation: Neurons develop into functioning cells.

Question 35

What occurs during the differentiation stage?

Answer 35

During differentiation, neurons start forming dendrites, axons, and ion channels, and cease further division.

Question 36

What is cortical dysgenesis?

Answer 36

Cortical dysgenesis is improper layer formation linked to various human syndromes, with varying degrees of severity.

Question 37

What is lissencephaly?

Answer 37

Lissencephaly is an extreme form of cortical dysgenesis where the cortex layers are disorganized, resulting in a smooth cortex with few sulci.

Question 38

What is axon guidance?

Answer 38

Axon guidance is the process by which axons determine their direction of growth, guided by molecules in the environment.

Question 39

How do axons stick together?

Answer 39

Axons stick together via cell adhesion molecules (CAMs), allowing them to grow together and form fasciculations.

Question 40

What happens when axons become myelinated?

Answer 40

When axons become myelinated, they form white matter tracts.

Question 41

What is synaptogenesis?

Answer 41

Synaptogenesis is the formation of synapses between neurons.

Question 42

How does communication between neurons occur?

Answer 42

Communication occurs via neurotrophic factors secreted by neurons.

Question 43

What happens to inappropriate synapses?

Answer 43

Inappropriate synapses are lost through pruning, and some neurons may undergo apoptosis.

Question 44

When can apoptosis occur pathologically?

Answer 44

Apoptosis can occur pathologically in conditions such as Alzheimer’s and Parkinson’s.

Question 45

What is the importance of gene expression in CNS development?

Answer 45

CNS development relies on correct gene expression and proteins, with potential for errors due to mutations or environmental changes.

Question 46

What are some conditions with a neuro-developmental aspect?

Answer 46

Conditions include Autism, Schizophrenia, Cerebral Palsy, Cerebellar Ataxia, Dyslexia, and Epilepsy.