How does our brain develop throughout our lifetime? Flashcards
Nervous System is organized at all stages
-During all stages of development, nervous system is highly organized
-Organization is result of:
–Genes
–Environment & Experience
–Interaction of the two
Prenatal Nervous System Development
-nervous system develops from the ectoderm (18 days of gestation)
-Embryo = 3 layer disk
–Ectoderm (nervous system & skin)
—-Neural Plate is formed by thickening of ectoderm, whole process called “Neurulation”
–Mesoderm (skeleton & muscles)
–Endoderm (internal organs)
Neural Groove (20 days)
-Uneven rates of cell division in the neural plate cause formation of Neural Groove —- future CNS (brain and spinal cord)
-Neural Crest cells are progenitors for entire PNS
Neural Tube
-Neural groove joins together to form Neural Tube with a fluid-filled Central Canal
-Central canal will form ventricles and spinal cord canal – cerebral spinal fluid
-Cells lining neural tube will be progenitors for entire CNS
-Cranial end forks out to form brain plate
Brain Structures that form at 24 days
-Cerebral cortex, Limbic system, Basal Ganglia
-Thalamus & Hypothalamus
-Substantia nigra & Ventral tegmental area
-Cerebellum, Pons, Medulla
-Cranial end of neural tube swells as a result of new cells being born (neurogenesis)
-Neural crest cells - Neurons of somatic and autonomic nervous system
22 days of gestation
-Neural groove joins together to form Neural Tube with a fluid-filled central canal
–Brain plate also forms (part of ectoderm that continues to get thicker
–Central canal will form the ventricles and spinal cord canal - cerebral spinal fluid
–Cells lining neural tube will be progenitors for entire CNS
-Cranial end forks out to form brain plate
25 days of gestation
Neural tube
40 days of gestation
Forebrain, midbrain, hindbrain, spinal cord
50 days of gestation (1st trimester)
-when it actually starts to look like a brain
-Diencephalon
-Telencephalon
100 days of gestation (1st trimester)
-(double gestation) you get an actual cerebral hemisphere and start to form hindbrain structures
-cerebellum
-pons
-medulla
2nd trimester
41 weeks is when brain looks like a normal one
6 Stages of Neural Development
- Neurogenesis - production of neuronal cells from non-neuronal precursors
- Cell migration - movement of cells to form distinct brain regions
- Differentiation - transformation of precursor cells into neurons & glia
- Synaptogenesis - establish synaptic connections
- Neuronal cell death - not all make it and some are marked for death
- Synapse rearrangement - loss or development of synapses, almost like pruning
Neurogenesis
-Most neurons generated before birth, some during childhood, and some during adulthood
-Cells lining central canal = ventricular zone
-Precursor cells divide symmetrically to expand ventricular zone (mitosis)
–Cells lining the central canal = ventricular zone
-Asymmetric division: Cell division switched to “asymmetric division”
–One daughter cell migrates out and one stays and continues to divide
–All cells develop here and then move away
Cell migration
-Cells move away from the ventricular zone
-What brain region a cells ends up in is dictated by where it was born in the ventricular zone
-Radial glial cells act as guides → These cells connect the ventricular zone with a particular spot in the marginal zone
-This migration is directed by cell adhesion molecules (CAMS)
-As the marginal zone fills, produces cortical plate
-As neurons migrate, they push past previous neurons to populate the outermost part of the cortical plate
-This is how we get six layers of the cortex – waves of cells form the laminar
structure in an inside-out manner
Differentiation
-When cells arrive at destination, they begin to express genes to make the specific proteins they need
-They differentiate – take on a specific final morphology (glia, neurons, and particular subtypes of each)
-What controls what a cell will differentiate into?
–Intrinsic factors – internal genetic/molecular signals
–Extrinsic factors – molecular/chemical influences around cell
