Development of the Nervous System & Clinical Correalates in Padiatrics

Question 1

When does development of the human brain begin and continue up until ?

Answer 1

Beings 3rd week post conception and continues well into late adolescence/early adulthood and beyond

Question 2

What is brain development influenced by ?

Answer 2

Genes and environment (both intruterine and extrauterine)

Question 3

What does genes determine in terms of brain development ?

Answer 3

• The correct sequence and evolution of brain development
• Development of dendritic and axonal interconnections
• Development of synapses, receptors and neurotransmitters

Question 4

What factors affect the intrauterine environment hence affecting brain development ?

Answer 4

• Maternal health and disease
• Insults e.g. alcohol and cytomegolovirus
• Placental function and fetal nutrition

Question 5

What factors affect the extrauterine environment and hence affecting brain development ?

(believe this is more after the pregnancy phase)

Answer 5

• Physical factors such as Nutrition, environmental toxins
• Emotional and social factors e.g. neglect and lack of stimulation

Question 6

What are the 3 main phases or brain development ?

Answer 6

• The embryonic period (conception to week 9) - believe development it starts at week 3 in this phase
• Fetal development (week 9 to 40/42)
• Post natal development

Question 7

Describe the embryonic period

Answer 7

• 2 layered embryo
• Epiblast and hypoblast
• Primitive streak and primitive node
• Migration of cells through streak then rostral-caudal migration
• determined by nodal signalling

Question 8

Describe gastrulation

Answer 8

Results in the development of the following three layered embryo:

• Ectoderm - Skin nails hair and neural tissue
• Mesoderm - muscle bone cartilage and vascular system
• Endoderm - gut and resp system

Question 9

What is the first well defined neural structure to form in brain development ?

Answer 9

The neural tube

Question 10

What lines the neural tube ?

Answer 10

Neural progenitors - this lining of the neural tube is termed the ventricular zone

Question 11

What does the hollow centre of the neural tube develop into ?

Answer 11

Ventricular system and central channel of the spinal cord

Question 12

What does the caudal tube develop into ?

Answer 12

The spinal cord

Question 13

What does the anterior/rostral tube develop into ?

Answer 13

The brain

Question 14

Define what neural patterning is

Answer 14

It is the biological process by which cells in the developing nervous system acquire distinct identities according to their specific spatial positions.

E.g.

• High conc. Pax6 with low conc. of Emx2 induce progenitor to differentiate into motor neurons
• Low conc. Pax6 and high conc. Emx2 induce visual cortical neurons

Question 15

Describe what happen during the foetal period ?

Answer 15

• Brain is initially smooth in contour, develops gyri and sulci.
• Neuronal progenitor cells in the ventricular zone divide initially ‘symmetrically’
• Then Asymmetrical cell division then follows i.e. cell division produces one progenitor cell and one neuron
• Progenitor cells continue to divide in the ventricular zone producing more cells
• Neurons migrate to take their place in the developing neocortex

Question 16

Describe what is neuronal migration

Answer 16

It is the method by which neurons travel from their origin or birthplace to their final position in the brain. There are several ways they can do this, e.g. by radial migration or tangential migration.

Question 17

How does networking and information sharing arise ?

Answer 17

Once neurons reach their target cortical regions they develop processes which allow them to communicate and transmit information between neurons.

Question 19

Neurons have axons and dendrites what are there functions ?

Answer 19

Axons:

• Transmit signals from neurons
• Synapses develop when connected with another neuron

Dendrites:

• Gather info and transmit to neurons

Question 20

Describe the process of myelination (this is postnatal now)

Answer 20

OPC’s (oligodenrdrocyte progenitor cells/OPC’s) develop processes which wrap around axons > myelin sheaths. These sheaths increase axon conduction.