Lecture 9 Brain Development

Question 1

Key Brain Development Processes

Answer 1

1. Neurogenesis (neuron creation)
2. Myelination (axon insulation)
3. Synaptogenesis (synapse formation)
4. Synaptic pruning (eliminating unused synapses)
5. Apoptosis (programmed cell death)
6. 神经发生（神经元生成）
7. 髓鞘形成（轴突绝缘）
8. 突触形成（突触形成）
9. 突触修剪（清除未使用的突触）
10. 细胞凋亡（程序性细胞死亡）

Question 2

Adult Human Brain Composition

Answer 2

1.3kg; 60% fat, 40% water/proteins/salts; trillions of specialized cells

Question 3

Grey vs. White Matter

Answer 3

Grey matter (outer layer, cell bodies) vs. white matter (inner myelinated axons) – reversed in spinal cord

Question 4

Enteric Nervous System (ENS)

Answer 4

‘Second brain’ in GI tract; 400-600M neurons; regulates digestion; produces 90% of body’s serotonin

Question 5

Neuron Types

Answer 5

1. Sensory (input) 2. Motor (output – upper/lower) 3. Interneurons (connections)

Question 6

Neuron Structure

Answer 6

Soma (cell body), dendrites (receive signals), axon (sends signals)

Question 7

Glial Cell Types/Functions

Answer 7

Astrocytes (nutrient support), Oligodendrocytes/Schwann cells (myelin), Microglia (immune), NG2+ (precursors)

Question 8

Brain Growth Timeline

Answer 8

35% adult size at birth → 80% by age 2; grey matter peaks in childhood, white matter peaks ~age 30

Question 9

Neurulation

Answer 9

Neural tube forms at 2-3 weeks gestation; vulnerable to toxins

Question 10

Neurogenesis

Answer 10

Neuron creation from stem cells; peaks at 28 weeks gestation; continues in hippocampus/amygdala (mood/memory)

Question 11

Arborization

Answer 11

Dendrite branching → increased synaptic connections; rapid growth from 28 weeks gestation

Question 12

Myelination Process

Answer 12

Oligodendrocytes wrap axons; begins prenatally, continues to adulthood; sensory areas mature first

Question 13

Myelination Impact

Answer 13

Enhances processing speed; underlies Theory of Mind development; frontal cortex completes last (~age 30)

Question 14

Synaptogenesis

Answer 14

Forms trillions of connections; peaks at 34 weeks gestation (40K synapses/sec); varies by brain region

Question 15

Synaptic Pruning

Answer 15

Eliminates 40% unused synapses; continues into 30s; atypical pruning linked to ASD (reduced) and schizophrenia (excessive)

Question 16

Critical Period Example

Answer 16

Dark-reared chimps: retinal atrophy irreversible if light deprived >7 months (human cataracts show similar effects)

Question 17

Experience-Dependent Plasticity

Answer 17

Rich environments → thicker cortex, more synapses (e.g., rats in complex cages)

Question 18

Prefrontal Cortex Maturation

Answer 18

Last to mature (executive functions); synaptic pruning continues until 30s