Development of the nervous system Flashcards
When does human brain development begin?
3rd week post conception and continues well into late adolescence/ early adulthood
What do genes determine in the development of the brain?
Correct sequence and evolution of the brain from conception to neural proliferation, migration and reorganisation
Development of dendritic and axonal interconnections
Determine the development of synapses, receptors and neurotransmitters
What can influence nervous system development intrauterine?
Maternal health and disease
Insults which may be continuous throughout pregnancy - alcohol exposure, cytomegalovirus
Placental function and fetal nutrition
What can influence nervous system development extrauterine?
Physical factors such as nutrition, environmental toxins
Emotional and social factors e.g. neglect and lack of stimulation
Exposure to drugs, alcohol and other related substances
What is considered the embryonic period?
Conception - 8 weeks
What makes up the embryo?
Epiblast and hypoblast
Primitive streak and primitive node - cells migrate through the streak then rostral-caudal migration determined by nodal signalling
What is gastrulation?
Formation of germ layers - ectoderm, mesoderm and endoderm
What will ectodermal tissue become?
Skin
Nails
Hair
Neural
What will mesodermal tissue become?
Muscle
Bone
Cartilage
Vascular system
What will endodermal tissue become?
Gut
Respiratory system
What is the first well defined neural structure to form?
Neural tube
When does the neural tube form?
Day 20-27
What lines the neural tube?
Neural progenitors - ventricular zone
What will the hollow centre of the tube become?
Ventricular system and central channel of the spinal cord
What will the anterior tube become?
Brain
What will the caudal tube become?
Spinal cord
What are the characteristics of the surface of the brain at week 9?
Initially smooth (lissencephalic) and gradually develops its folded appearance (sulcal and gyral pattern)
What occurs during weeks 8-26 of foetal brain development?
Primary sulci e.g. longitudinal fissure, sylvian cingulate, parieto-occipital and calcarine, temporal
What occurs during weeks 30-35?
Secondary sulci
What occurs during weeks 36-post natal period and early infancy?
Tertiary sulci
Why are gyri and sulci needed?
To accommodate the proliferating neuronal populations
Where do neurones migrate to?
Neocortex
What occurs when neurones reach their target cortical regions?
They develop processes which allow them to communicate and transmit information between neurones
What do axons do?
Transmit signals from neurones
Guidance molecules determine path
Synapses develop when connected with another neuron
What do dendrites do?
Gather info and transmit to neurones
Multiple dendrites from arbors around the neuron
What percentage of neurones will die?
50% mostly prenatally
What percentage of synaptic connections will be eliminated?
50%, postnatally and ongoing throughout life
What occurs postnatally in brain development?
Postnatal proliferation and migration
Myelination
What parts of the brain will develop post-natally?
Olfactory bulb
Dentate gyrus of the hippocampus
Glial progenitors become oligodendorocytes and astrocytes
What cells will develop myelin sheaths?
Oligodendrocytes
What is the purpose of a myelin sheath?
Increase axonal conduction dramatically Maintain axonal integrity Survival Neuronal size Axonal diameter
What way will axons become myelinated?
Sequential manner from bottom to top and from back to front
What impact does experience have on the development of the brain?
Essential for emergence of normal neocortical patterns
When input is lacking, the brain areas develop differently
Specific patterns of development reflect the kinds of input the infant and child receive
Enrichment and deprivation
What are the developmental tasks of the adolescence?
Establish nurturing and intimate relationships Development of identity Future perspectives Self-confidence Self control Social skills
What occurs in the brain during adolescence?
Many synapses are eliminated
Increase in white matter volume
Changes in neurotransmitter systems
What type of receptors is the brain full of?
Steroid receptors - therefore the rising gonadal hormone concentrations in teenage years affect the brain
What differing effects do estrogen and androgens have on the brain?
Oestrogens make girls more prone to stress
Androgens make boys more resilient to stress
What insults to the brain can occur?
Insults within first few weeks not compatible with life: neural tube formation, brain vesicles, migrational disturbances
What problems can occur with neural tube formation?
Anencephaly
Spina bifida
What is holoprosencephaly?
Failure of brain vesicles to form
What are the different disorders of myelination?
Hypomyelination
Dysmyelination
Demyelination
What is the PLP1 gene?
Encodes a transmembrane protein, the predominant myelin protein in the CNS. It is responsible for compaction, stabilization and the maintenance of myelin sheaths, oligodendrocyte development and axonal survival
Where is the PLP1 gene located?
X chromosome
What is the most severe PLP1 gene?
Pelizaeus-merzbacher
What will pelizaeus-merzbacher present as?
Nystagmus Hypotonia Cognitive impairment Severe spasticity Ataxia
What impact will malnutrition have on brain development?
Brain growth and volume
Myelination
Lack of energy and deprivation - lack of postnatal stimulation and experiences
