L4 - How does the Nervous System Develop

Question 1

3 stages of prenatal development:
germinal stage

Answer 1

conception - 3 weeks
implantation in uterus wall
zygote travels down fallopian tube to uterus
cells multiply rapidly
cells differentiate

Question 2

3 stages of prenatal development:
embryonic stage

Answer 2

3-9 weeks
period of rapid cell division & differentiation - embryo takes human shape
- amniotic sac
- placenta
- umbilical cord
organism divides into 3 layers
- ectoderm: hair, teeth, outer skin layer, NS
- mesoderm: inner skin layer, skeleton, muscles
- endoderneural tube: vital organs, glands, gastrointestinal tract

Question 3

3 stages of prenatal development:
foetal stage

Answer 3

9 weeks - birth
period of continuous growth for major structures & systems
major feature = begin development

Question 4

nervous system development in the womb:
first 3 weeks

Answer 4

ectoderm thickens & becomes neural plate
sphere dividing cells flatten & outer layers thicken
neural plate fold to form neural groove then closes over to form & fluid-filled cylinder - neural tube

Question 5

nervous system development in the womb:
week 4 to birth

Answer 5

embryo: up to 10 weeks
foetus: w 10 to birth
week 4 main divisions of CNS formed
mid-pregnancy cerebral hemispheres expanded to cover rest of brain
6 months cell proliferation -> infolding -> sulci & gyri on surface of cortex
lobes can be differentiated

Question 6

7 stages:
1. cell birth - neurogenesis

Answer 6

non neural cells divide by mitosis to produce neurons
single layer of cells along inner surface of neural tube -> ventricular zone
neurons & glial cells come from here

Question 7

7 stages:
2. cell migration

Answer 7

cells move to establish distinct nerve populations e.g. layers of cerebral cortex
newly formed cells move from ventricular zone to correct destination in NS
travel along radial glial cells - guides

Question 8

7 stages:
3. cell differentiation

Answer 8

cells acquire distinctive characteristics e.g. neurons - result of expressing particular genes
cells reach destinations & start to express particular genes
cell-cell interaction coordinates development - ensures right type of neuron for that part of brain

Question 9

7 stages:
4. cell maturation

Answer 9

dendrite & axon growth

Question 10

7 stages:
5. synaptogenesis

Answer 10

formation of synapses

Question 11

7 stages:
6. cell death & synaptic pruning

Answer 11

‘use it or lose it’ synaptic connections that don’t become part of a functional neural network are lost
synaptic pruning & maturity proceed at different rates in different brain areas

Question 12

7 stages:
7. myelination

Answer 12

axons become wrapped in fatty sheath
speeds conduction of electrical signals
prenatally; rapid shortly after birth; continues into adulthood