CNS Development Flashcards
when does brain development begin
3rd week post conception - continues into adolescence and beyond
what to genes determine when it comes to brain development
- correct sequence and evolution of the brain (conception - neuronal proliferation -neuronal migration - reorganisation)
- development of dendritic and axonal interconnections
- development of synapses, receptors and neurotransmitters
what parts of the intrauterine environment can effect brain development
- maternal health and disease
- Insults which may be continuous throughout pregnancy (alcohol, infection)
- placental function and fetal nutrition
What parts of the extrauterine environment can effect brain function
physical factors eg. nutrition, environmental toxins
emotional and social factors eg. neglect and lack of stimulation
exposure to drugs, alcohol and other related substances
how long is the embryonic period
8 weeks (conception - 8 weeks)
what is inside the uterus in the embryonic phase
a 2 layered embryo made up of the epiblast and hypoblast
where do cells migrate through in the embryo
the primitive streak
what happens during gastrulation
development of 3 layers
ectoderm - hair, skin, nails
mesoderm - muscles, bone, cartilage
endoderm - gut and respiratory system
What is the first well defined structure to form and when
the neural tube - forms around 20-27 days
what leads to neural tube formation
neural progenitor cells from the neural place form a grove, which then forms a tube, which then goes on to form the neural crest
what is the ventricular zone
the outside of the neural tube - lined with neural progenitors
what does the hollow structure inside the neural tube become
the Ventricular system
what does the central channel of the neural tube become
the spinal cord
what are the primary brain vesicles and when do they occur
occur at 3/4 weeks
prosencephalon (forebrain)
mesencephalon (midbrain)
Rhombencephalon (hindbrain)
what are the secondary brain vesicles and when do they occur
occur at 5 weeks
Tencephalon Diencephalon Mesencephalon Metencephalon Myelencephalon
what is neural patterning in the embryo
complex and continuous refinement of neural pattern development
what is the neocortex
part of the brain concerned with vision and hearing
what does high EMX2 and low PAX6 lead to in the neocortex
neural progenitor cells differentiated into visual cortex neutrons
what does low EMX2 and high PAX6 lead to in the neocortex
neural progenitor cells differentiate into motor neurons
when is the fetal period
week 9/10 till birth
what does the brain look like before it folds into a sulcal gyral pattern
smooth
when do the primary sulci develop
8-26 weeks
when do secondary sulci develop
30-35 weeks
when do tertiary sulci develop
week 36 onwards into post natal and early infancy
how to neural progenitor cells in the ventricular zones divide to begin with
symmetrically - division produces 2 progenitor cells
how do neural progenitor cells in the ventricular zone divide later
asymmetrically eg. cell division produces one progenitor cell and one neuron
where do the neurons produces in the ventricular zones migrate to
the developing neocortex
3 methods of neural migration
Somal translocation
radial glial guides
tangential migration and signalling pathways
what happens to neurons once they reach their target cortical region
they form axons and dendrites so they can communicate with each other
what’s the function of axons
transmit signals from neurons
develop synapses when connected to other neurons
long bit
What’s the function of dendrites
gather information and transmit it to the neuron
multiple dendrites form around the neuron
star bit lol
where do neurons in the ventricular zones migrate to in postnatal brain development
olfactory bulb
dentate gyrus of the hippocampus
what is mylelination
when oligodendrocyte progenitor cells develop processes which wrap around axons forming a myelin sheath
what are the functions of the myelin sheath
greatly increased axonal conduction
maintains axonal integrity and survival
maintains neuronal size and axonal diameter
at what age does most myelination occur
first 2 years
why is postnatal experiences needed for brain development
to allow for mature organisation - learning from experiences leads to synaptic pruning
what developmental tasks are adolescents aiming to achieve
- establishing nurturing and intimate relationships
- developing identity
- future perspectives
- independence
- self confidence
- self control
- social skills
what happens to the brain in adolescence
many synapses are eliminated
theres an increase in white matter volume
changes in neurotransmitter systems
what are grey and white matter
grey matter - contains cell bodies/where the synapses are
white matter - axons connecting different parts of grey matter together
how do hormones affect the teenage brain
rise of steroid hormones in puberty affects the brain as it is full of steroid receptors. This causes restructuring and permanent reorganising
what happens when there is monocular visual deprivation in early post natal life
one eye is blocked so the other eye takes over the visual cortex area usually occupied by the blocked eye
what is anencephaly
absence of a major portion of the brain, skull and scalp due to a neural tube defect
what is spina bifida
gap in the spine due to baby’s spinal cord not developing
what is holoprosencephaly
failure of development of the procephalon (embryological forebrain) to sufficiently divide into the double lobes of the cerebral hemisphere
what is hypomyelination
inherited condition causing abnormally low amounts of myelination
what is dysmyelination
malformed and defective myelin sheath
what is demyelination
destruction of myelin that surrounds axon - example is MS
what does the PLP1 gene encode for
a transmembrane proteolipid protein which is a prominent myelin protein (located on X chromosome)
what is Pelixaeus-Merzbacher disease
mutation in PLP1 gene causing shortened life span.
Presents in infancy with hypotonia and cognitive impairment
What is spastic paraparesis 2
a less severe mutation of the PLP1 gene which manifests as spastic paraperisis with or without CNS involvement
how does malnutrition affect brain development
impacts brain growth and volume
impacts myelination
lack of energy due to malnutrition can lead to a lack of postnatal experiences
