Neurodevelopment

Question 1

At what point does an embryo technically become a foetus?

Answer 1

8 weeks

Question 2

Describe the germinal stage

Answer 2

The egg and the sperm nuclei fuse to form a zygote. After 12 hours it starts to divide. After 6 days it implants into the uterus lining

Question 3

Describe the embryonic stage

Answer 3

By 2 weeks there are 3 distinctive cell layers; ectoderm, mesoderm and endoderm. The neural groove is developed. Neural ridges form the neural tube which forms the ventricles and the central canal of the spinal chord

Question 4

Describe the ectoderm cell layer

Answer 4

This goes on to form the nervous system, mainly the early brain;
Forebrain - diencephalon and telencephalon
Midbrain - mesencephalon
Hindbrain - rhombencephalon

Question 5

Describe the mesoderm cell layer

Answer 5

This goes on to form bone and muscle tissue

Question 6

Describe the endoderm cell layer

Answer 6

This goes on to form the digestive and respiratory systems

Question 7

Describe Spina Bifida

Answer 7

The failure of the neural fold to close at the spinal chord, leaving an opening exposing the spinal chord. This can lead to paralysis and limb deformities

Question 8

Describe Anencephaly

Answer 8

This is where parts of the brain and skull fail to develop, due to a neural tube defect

Question 9

Describe neurogenesis during foetal development

Answer 9

Neurones are formed by the mitotic division of non-neuronal cells, these new cells migrate out of the ventricular zone

Question 10

Describe cell migration during foetal development

Answer 10

Massive movement of neurones to establish distinct populations, cells climb along radial glial cells guided chemically by adhesion molecules

Question 11

Describe cell differentiation

Answer 11

Cells become distinctive types of neurones or glial cells, they start to express particular genes in particular locations

Question 12

Name the 2 ways cells can become differentiated

Answer 12

• Cell-autonomous manner

- Induction

Question 13

Describe cell-autonomous differentiation

Answer 13

The process of differentiation is directed by the cell itself

Question 14

Describe induction differentiation

Answer 14

The process is influenced by neighbouring cells, they recognise their context and differentiate in the appropriate way

Question 15

Describe synaptogenesis and define filopodia

Answer 15

The formation of new synapses and axons and the development of dendrites
Filopodia > an outgrowth from the tips of axons and dendrites

Question 16

Name some causes of neuronal degeneration

Answer 16

Head injury, tumour, infection, toxic substances and ageing

Question 17

What is neurogenesis?

Answer 17

The peak of prenatal brain development where 250,000 are created every minute, by birth most of the cells have been created

Question 18

What cells continue to have neurogenesis throughout life?

Answer 18

Olfactory receptors and neurons as well as hippocampal and cortical neurons

Question 19

What is neuroplastic degeneration?

Answer 19

Damage to the cell body which results in neuronal death

Question 20

What is anterograde degeneration?

Answer 20

Axonal damage towards the terminals decreasing connectivity

Question 21

What is retrograde degeneration?

Answer 21

Axonal damage towards the soma leading to cell death

Question 22

What is neuroplastic regeneration and how does it take place?

Answer 22

The birth of new cells;

Nerve growth factors + stem cells + electrical impulse = regeneration

Question 23

What do nerve growth factors do?

Answer 23

Regulate axonal and dendritic growth, the formation of synaptic structure and connections and neurotransmitter release

Question 24

Describe collateral sprouting

Answer 24

Increased connectivity in neurons due to axonal sprouting, may be activity dependent as can be induced by electrical stimulation

Question 25

How can neuroplasticity be used to help patients with Parkinson’s disease?

Answer 25

The direct implantation of foetal or stem cells into the CNS can restore some motor function

Question 26

How can the environment an animal is raised in affect its brain development?

Answer 26

In an enriched environment rats were found to have more neurons, larger dendritic fields and greater connectivity

Question 27

What is foetal alcohol syndrome?

Answer 27

Neurotoxic damage caused to the child while in the uterus which can affect growth of the brain, language skills and facial features

Question 28

What is anoxia?

Answer 28

Where there has been a lack of oxygen to the child in utero resulting in cerebral palsy

Question 29

What is the cause of autism?

Answer 29

A period of rapid brain growth, initially it is smaller but by 1 year of age it becomes abnormally large, with increased weight and tissue volume

Question 30

What are some developmental causes of learning difficulties?

Answer 30

• genetic abnormality (chromosomal or metabolic)
• abnormal embryonic development
• prenatal disease/infection
• birth trauma (anoxia)
• malnutrition
• sensory deprivation

Question 31

What deficits are observed with age associated memory impairment?

Answer 31

• free and cued recall
• recollection of event context
• prospective memory tasks
• working memory tasks

Question 32

Describe the features of Alzheimer’s disease

Answer 32

Progressive and relentless cognitive decline, frontal, temporal and parietal atrophy, accumulation of amyloid plaques in the cell soma and an increase in neurofibrillary tangles

Question 33

What are telomeres?

Answer 33

The section at the end of the chromosome which shortens after every replication (thus the Hayflick limit)
Cancer cells create telomerase so over-replicated