Neurodevelopment Flashcards
At what point does an embryo technically become a foetus?
8 weeks
Describe the germinal stage
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
Describe the embryonic stage
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
Describe the ectoderm cell layer
This goes on to form the nervous system, mainly the early brain;
Forebrain - diencephalon and telencephalon
Midbrain - mesencephalon
Hindbrain - rhombencephalon
Describe the mesoderm cell layer
This goes on to form bone and muscle tissue
Describe the endoderm cell layer
This goes on to form the digestive and respiratory systems
Describe Spina Bifida
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
Describe Anencephaly
This is where parts of the brain and skull fail to develop, due to a neural tube defect
Describe neurogenesis during foetal development
Neurones are formed by the mitotic division of non-neuronal cells, these new cells migrate out of the ventricular zone
Describe cell migration during foetal development
Massive movement of neurones to establish distinct populations, cells climb along radial glial cells guided chemically by adhesion molecules
Describe cell differentiation
Cells become distinctive types of neurones or glial cells, they start to express particular genes in particular locations
Name the 2 ways cells can become differentiated
- Cell-autonomous manner
- Induction
Describe cell-autonomous differentiation
The process of differentiation is directed by the cell itself
Describe induction differentiation
The process is influenced by neighbouring cells, they recognise their context and differentiate in the appropriate way
Describe synaptogenesis and define filopodia
The formation of new synapses and axons and the development of dendrites
Filopodia > an outgrowth from the tips of axons and dendrites
Name some causes of neuronal degeneration
Head injury, tumour, infection, toxic substances and ageing
What is neurogenesis?
The peak of prenatal brain development where 250,000 are created every minute, by birth most of the cells have been created
What cells continue to have neurogenesis throughout life?
Olfactory receptors and neurons as well as hippocampal and cortical neurons
What is neuroplastic degeneration?
Damage to the cell body which results in neuronal death
What is anterograde degeneration?
Axonal damage towards the terminals decreasing connectivity
What is retrograde degeneration?
Axonal damage towards the soma leading to cell death
What is neuroplastic regeneration and how does it take place?
The birth of new cells;
Nerve growth factors + stem cells + electrical impulse = regeneration
What do nerve growth factors do?
Regulate axonal and dendritic growth, the formation of synaptic structure and connections and neurotransmitter release
Describe collateral sprouting
Increased connectivity in neurons due to axonal sprouting, may be activity dependent as can be induced by electrical stimulation
