Neurological development Flashcards
Why is understanding brain development important?
It helps understand different stages of development and evolution of brain structures and functions.
It allows for diagnosing and explaining structural and functional anomalies related to fetal development disorders.
It helps understand congenital conditions that affect the nervous system.
What factors can cause errors in brain development?
Exposure to teratogens
Genetic anomalies or mutations
What deficits can result from errors in brain development?
Sensory, motor, behavioral, or cognitive deficits
How do teratogens affect brain development?
The effects depend on dose, timing, and duration of exposure.
Exposure after the critical prenatal period can lead to intellectual, emotional, and behavioral disabilities.
What is the critical prenatal period for brain development?
From 2 to 18 weeks of gestation
What are the three key prenatal stages of brain development?
Embryonic stage (3-8 weeks)
Fetal stage (9-38 weeks)
Postnatal development
What happens during the first days of embryonic development?
The zygote undergoes division and becomes a blastocyst.
The blastocyst contains the inner cell mass (ICM) and is lined by trophoblasts.
Implantation occurs.
What happens when the inner cell mass (ICM) reorganizes?
It forms a bilaminar embryonic disc:
- Epiblast → Gives rise to the entire embryo
- Hypoblast → Forms the yolk sac
What role do trophoblasts play in early development?
They form the trophectoderm, which later develops into the placenta.
What is gastrulation, and when does it occur?
It occurs on day 16 when the bilaminar embryonic disc transitions into a trilaminar disc.
What are the three germ layers formed during gastrulation and their derivatives?
Endoderm → Digestive & respiratory system linings, glands
Mesoderm → Muscles, bones, cardiovascular system, blood
Ectoderm → Nervous system, epidermis, connective tissues
What is neural induction, and when does it occur?
Occurs on day 17
The ectoderm differentiates into:
- Neural ectoderm → Forms the neural plate
- Non-neural ectoderm → Forms the epidermis
What is neurulation, and when does it occur?
The transformation of the neural plate into the neural tube through bending, folding, and fusion.
Primary neurulation (weeks 3-4) forms the brain and most of the spinal cord.
Secondary neurulation (weeks 5-6) forms the sacral region of the spinal cord.
What structures arise from neural crest cells?
Neurons and glia of the peripheral nervous system (PNS)
What is a neural tube defect?
A congenital birth defect where the neural tube fails to close properly.
What are the three primary brain vesicles formed from the anterior neural tube?
Forebrain (Prosencephalon)
Midbrain (Mesencephalon)
Hindbrain (Rhombencephalon)
What does the posterior neural tube develop into?
The spinal cord
What is neurogenesis, and when does it begin?
The formation of neurons and glia
Begins after the neural tube closure at 4 weeks after fertilization
When does neurogenesis peak?
Between the 5th week and 5th month of gestation
What is neuronal migration, and why is it important?
The process of neurons moving to their final position in the brain
It occurs in an inside-out manner during corticogenesis
What are some disorders caused by migration defects?
Lissencephaly (smooth brain)
Pachygyria (thickened gyri)
Polymicrogyria (excessive small gyri)
What is gliogenesis?
The formation of astrocytes, oligodendrocytes, and ependymal cells
When does gliogenesis occur?
After neurons develop (late prenatal and early postnatal period)
How do neurons extend their connections?
By sprouting axons and dendrites
The growth cone at the tip of the axon senses guidance cues to find its target
Why is apoptosis necessary in brain development?
It eliminates excess neurons and prevents erroneous or unnecessary connections
About 1/3 to 1/2 of neurons undergo apoptosis
What is synaptogenesis?
The formation of synapses between neurons and their target cells
What is synaptic pruning?
The elimination of inappropriate connections to refine neural circuits
When does synaptic pruning mainly occur?
Early childhood and puberty
What is synaptic refinement?
The reconfiguration of synapses morphologically and functionally
What are critical periods in brain development?
Timeframes when experiences have a significant impact on synaptic connections
Occurs between 6-12 months and throughout childhood
What is myelination?
The formation of the insulating myelin sheath around axons
What type of cells produce myelin in the CNS and PNS?
Oligodendrocytes → CNS
Schwann cells → PNS
What happens when myelination is impaired?
It leads to demyelinating disorders (e.g., multiple sclerosis) and hypomyelinating leukodystrophies
When does myelination occur?
Begins late embryonic period
Continues through early postnatal development and adolescence
