Week 4 - The biology of the developing nervous system Flashcards
What is a congential condition?
A condition which arises as a result of abnormal development and is therefore present at birth
What is a zygote?
A single cell created by the fusion of the sperm and egg
What does the term diploid mean?
The name given to a cell that carries two complete paired sets of chromosomes
What is a gamete?
A reproductive cell (sperm/egg)
What is a haploid cell?
One which carries only one set of unpaired chromosomes
What are somatic cells?
All cells other than the reproductive cells (gametes)
What are the two main phases of the cell cycle?
- Interphase
- Mitotic phase
Broadly speaking, what happens during the interphase part of the cell cycle?
The cell prepares to divide
Broadly speaking, what happens during the mitotic phase of cell division?
The cell divides
The S phase is part of which stage of cell division?
The mitotic phase
What happens during S phase?
The DNA within the cell is replicated, producing two complete copies
What does the term cytokinesis refer to?
The cell membrane pinching in around the middle of the cell and the cell splitting into two daughter cells
Is symmetrical or asymmetrical cell division the most important type?
Asymmetrical - it provides opportunity for cells to diversify into different types
What is a morula?
The ball of cells that reaches the uterus 3-4 days post fertilisation
What is a blastocyst?
The ball of cells that implants into the wall of the uterus
How is a blastocyst different from a morula?
A blastocyst has two different types of cells in it
What are the outer cells of blastocysts called?
Trophoblasts
What do trophoblasts go on to form after implantation?
The placenta
How many cells does the morula consist of?
16
What is gastrulation?
The formation of 3 distinct tissue source layers via cell diversification in a developing embryo
What are ectoderm cells?
Cells which will form skin, hair and the lining of structures such as the nose and mouth, and the nervous system
What are mesoderm cells?
A type of cell that forms the muscles, skeleton and blood
What are endoderm cells?
A type of cell that forms the lining of the respiratory tract, digestive tract and bladder
Around how long post fertilisation does the development of the nervous system begin?
18 days
In the developing nervous system, what is the tissue source layer that the neural plate arises from?
The ectoderm
What is the neural groove?
The first step in the formation of the nervous system
What is the role of the notochord during nervous system development?
It plays an important role in diverisfying and migrating cells
What orientation does the term ventral refer to?
Bottom or lower
What does the Sonic hedgehog gene do?
It codes one signal used by the notochord to help cells orient themselves during development
What is the reason for the name of the ‘Sonic hedgehog’ gene?
A mutant gene first found in fruit fly embryos causes the embryo to present a stunted and spiky appearance
What is the meaning of the term neural tube defect (NTD)?
Congenital conditions that occur when the neural tube does not close, leaving the neural tissue exposed to amniotic fluid
What happens if the neural tube does not close during development?
The neural tube will be exposed to amniotic fluid and neural tube defects are likely to occur
What is anencephaly?
A neural tube defect where the neural tube fails to close anteriorly
What condition occurs if the neural tube fails to close posteriorly?
Spina bifida
What are the three types of spina bifida?
- Spina bifida occulta
- Meningocele
- Myelomengocele
Of the three types of spina bifida, which is the most serious and why?
Myelomeningocele
It can cause severe disability, including paralysis of lower limbs
Low levels of which micronutrient can be a risk factor for spina bifida to occur?
Folic acid
Taking folic acid has been shown to reduce the risk of spina bifida by how much?
Up to 70%
What is the definition of genotype?
The complete code contained within the chemical composition of DNA
What does heritability refer to?
The extent to which a variation of a particular characteristic in a population can be determined solely by genes
With regards to heritability, what does a value of 1 mean?
That all of the variation in a population is determined by genes rather than environment
What does the term ‘fetal alcohol spectrum disorders’ (FASD) refer to?
A set of health conditions that occur in offspring that is related to the maternal consumption of alcohol
Which type of cells are most likely to be damaged by maternal alcohol consumption?
Brain and spinal cord cells - other cells take higher concentrations of alcohol to be damaged
In Western countries, roughly how many pregnancies are thought to be affected by FSAD?
1 in 500
Of all the possible substances of abuse, which can have the most wide-ranging consequences on the developing baby?
Alcohol
What characteristic facial feature can be seen in children with FASD?
Flattened nose bridge
Lack of ridge on upper lip
What can FASD sometimes be misdiagnosed as?
Autism spectrum disorder
Why are children with FASD sometimes misdiagnosed as having ASD?
Because the symptoms can manifest in very similar ways
What are the main symptoms FASD can cause?
- Language deficicts
- Attention problems
- Social problems
- Problems with sensory integration
- Poor reasoning
What conditions can often be co-morbid with FASD?
- ADHD
- Autism
During embryo development, what three regions does the neural tube segment into?
- Prosenchephalon
- Mesencephalon
- Rhombencephalon
During embryo development, what does the prosencephalon go on to become?
The forebrain
During embryo development, what does the mesencephalon go on to become?
The midbrain
During embryo development, what does the rhombencephalon go on to become?
The hindbrain
What are the five segments that form during secondary segmentation in embryo development?
- Telencephalon
- Diencephalon
- Mesencephalon
- Metencephalon
- Myelencephalon
What are neuromeres?
The segments in the developing nervous system
What is the prosencephalon?
The segment of the developing neural tube that goes on to form the forebrain
What is the mesencephalon?
The segment of the developing neural tube that goes on to form the midbrain
What is the rhombencephalon?
The segment of the developing neural tube that goes on to form the hindbrain and spinal cord
What is cell fate?
The final identity of type of a cell at the end of its cell lineage
What does totipotent mean?
A cell that is capable of becoming any type of cell within an organism, INCLUDUING placental cells
What is the trophoblast?
The layer of cells in a developing embryo that goes on to form the placenta
What does pluripotent mean?
A cell that is capable of becoming any type of cell within an organism, EXCEPT placental cells
What are the two tissue types that the blastocyst is formed of?
- Trophoblast cells
- Inner cell mass
What are bipotential progenitor cells?
Cells that can become one of two types of cell
What are progenitor cells?
Cells that become a specific type of cell
What are the only conditions under which it is permitted for embryos to be created, stored and used in a lab?
- Improving understanding of embryonic development processes
- Improving detection / understanding of human disease
- Developing treatments for human disease
- Providing advancesin understanding miscarriage, contracption techniques, treating infertility
What are radial glial cells?
Glial cells that provide a type of structural scaffold for migrating neurons to move along
How are neurons of the human adult cortex arranged?
In layers
How are the neurons of the cerebral cortex arranged?
In layers
When do the layers of the cerebral cortex start to form?
Around 6 weeks after fertilisation
What is the outer subventricular zone (oSVZ)?
A developmental region of the ventricular zone in the developing nervous system that is unique to primates
What is the outer subventricular zone important in the development of?
Cortical development
What is the inside-first outside-last principle of cortical development?
The way in which the cortex develops in its layered arrangement
During cortical development, which layers develop first and which last?
- First: innermost layers close to the ventricular zone
- Last: outermost layers
What are the two forms of cell migration in the human nervous system?
- Radial migration
- Tangential migration
What are the two types of cells that bipotential progenitor cells may go on to form?
- Neuron progenitor cells
- Glial progenitor cells
In which direction do neural progenitor cells move during radial migration?
Outwards from the ventricular zone surface
During tangential migration, in which direction do neural progenitor cells move?
Outwards and sideways
What is the pial surface?
The outer edge of the developing neural tube
What is nucleokinesis?
The process that occurs when the nucleus of a migrating cell moves into the leading arm
What is the name for the process in which neuronal migration occurs?
Leading process
How does neuronal migration occur?
Neurons extend an arm which is able to sense chemical signals arising in the surrounding tissue
What is the chemical known as semaphorin 3A used by neurons for?
To determine how far away from the pial surface they are
What is chemotactic guidance?
The use of chemical cues as a guide during cell migration
What are the two neuronal processes (projcetions from the cell body)?
- Axons
- Dendrites
Of the two neuronal cell body projections (processes), which one receives information from synapses and passes it on to the cell body for processing?
Dendrites
Of the two neuronal cell body projections (processes), which one passes on the integrated information from the cell body to different synapses?
Axons
What is meant by the term neurite?
A collective term given to either an axon or a dendrite of a neuron
Why are dendrites and axons collectively referred to as neurites sometimes?
Because it is difficult to tell during development whether an extended process arising from a developing neuron is a dendrite or a neuron
What is a growth cone?
The end of a growing axon that causes the axon to elongate and reach other neurons to form synaptic connections
What are filopodia?
Thin projections extending frmo the edge of migrating cells that sense the surrounding environment
What term is used to describe the formation of new synaptic connections?
Synaptogenesis
What component of a cell is responsible for making proteins?
The ribosome
Where are instructions located for making proteins
In the DNA in the nucleus of the cell
How does the ribosome get the instructions it needs to begin making the proteins that will be involved in neuronal communication?
Through mRNA, which transcribe the coded instructions from DNA and carry them to the ribosome
What is a key molecule for signalling synaptogenesis?
Brain-derived neurotrophic factor (BDNF)
What is brain-derived neurotrophic factor (BDNF)?
A key molecule for signalling synaptogenesis and neurogenesis
Brain-derived neurotrophic factor (BDNF) is thought to play a key role in which condition?
Depression
