Task 3 Flashcards
Growth and develoment of tghe brain through weeks
Week after fertilization- Embryo show the beginnning of all tissues, that consists of three cell layers: Mesoderm, ectoderm, and endoderm.
20 days after fertilization - Cell layers thicken and grow into a flat oval plate, creatin g a neuronal groove.
22 days after fertilization: Ridges of neural groove come together to form neural tube, a structure with subdivisions that correspond to the future forebrai n, midbrain and hindbrain.
24 days after fertilization- Interior of neural tube becomes fluid filled cerebral venricles of the brain, central canal of sponal cord and passages connecting them.
8th week- Embryo shows beginning of most body organs by this time the head is half the total size of the embryo
10th week onwards From this week, we start calling it a fetus. Until week 41 the fetus will undergo changes especially when it comes to the emergence of giry and sulci, which is done gradually.
Development of tthe nervous system
The development of the the nervous system can be divided into six distinct cellular stages:
Neurogenesis
Cell migration
Differentation
Synaptogenesis
Neuronal cell death
Synapse rearrangement
Neurogenesis
Ventricular zone
Cell to cell interactions
If at birth we havle already generated most of our cells why does the brain keep expanding?
What is adult neurogenesis?
Mitotic divsion of non neuronal cells to produce neurons
Once mitosis is over cells gradually form:
The ventricular zone is the region lininng cerebral ventricles that displays mitosis, providing neurons early in development and glial cells throughout life.
Then the celss sort themselves out via :
cell toceel inteeractions: proccess i which one cell affects the differentiation of another, usually beighboring, cells.
The brain keeps growing is due to the growth of neurons, branching of dendrites, elaboration of synapses, an increase in myelin and the addition of glial cells.
Adult neurogenesis is the generatio of new neurons in some areas of the adult brain, mostly the hippocampus and the olfactory organ
Cell migration
Radial glial cells
Cell adhesion molecules
Movements of cells to establish different nerve cell populations. It goes from site origin to final location.
At birth almost all future neurons have copmpleted their migration
Cells of cerebrzal cortex arrive in waves, with each wave forming a new outer layer, until six cortical layers of adult cortex are formed.
Radial glial cells they extend from inner to outer surfacte of the emerging nervous system, spanning the width of the emergin gcerebral hemispheres and guide migrating neurons
Cell adhesion molecules are proteins on the surface of a cell guiding migrating cells and/or axonal pathfinding. It promotes the adhesion of developing elements of the nervous system.
Differentiation
Cell autonomus differentiation
Induction
Transformation of precursor cells into distinctive types of neurons and glial cells.
Once cells reach their destination, they transcribe a particular subset of genes to make specific proteins they need.
Cell autonomus differentiation = cell proccess directed by the cell itself rather than influenced by other cells
Induction= Proccess by which a set of cells influences the fate of neighboring cells, usually by secreting chemical factors that cahnge gene expression in target cells.
Synaptogenesis
Growth cones and Filopodias
Establishment of synaptic connections as axons and dendrites grow
Growth cones: Specialized swellings(growing tips) of an axon or dendrite
Filopodia is a fine tubular outgrowth from the growth cone
Neuronal cell death
Whichh neurons die and which ones dont?
Neurotrophic factors
Selective death of many nerve cells
Cell death= Apoptosis= the develomental proccess during which susplus cells die
Durinngprenatal develoment most of the young nerve cells die
neurons that make synapses adequatley survive and grow those that fail to do so die
Neurotrophic factors= Targert derived chemical that acts as if it feeeds certain neurons to help them survive
neurons compete for it those that fail to receive enough die
role of the neurotrophic factor is to guide rearrangement of the synaptic connections
Gllial cells and myelin
Myelination has a strong impact on behavior because it allows large networks of cells to communicate rapidly
Myeli formation
Repeated wrapping of cythoplasm of scwann celss around the peripheral axon
Multiple sclerosis
Disorder in which myelin is destroyed by persons immune system in random distinct patches.
Results in deffects in neural communication and disruptions of sensory and motor functions.
How do glial cells origin? what do they do later?
Glial cells develop earlier from same populations of immature cells as neurons and continue to be added to the nervous system throughout life.
Periods of prenatal development
Germinal stage
Embryonic stage
Fetal stage
Germinal stage
Conception of two weeks, it begins with the conception and lasts until the zygote becomes implanted in th euterine wall its in this periods that rapid cell division takes place.
Embryonic stage
3rd t 8th week it follow implantation the major development toccurs in all the organs and systems of the body, development takes place through the proccesses of cell division, cell migration, cell differentiation, cell death as well as other hormonal influences.
Fetal stage
9th week to birth continues the develoment of physical structures and rapid growth of the body. Increzsing levels of behavior, sensory experience and learning.
