PSYCH 3313 Chapter 5

Neurodevelopment

The study of how the nervous system forms, develops, and changes throughout life.

Gastrulation

A stage in early embryonic development when the blastula reorganizes into three germ layers.

Ectoderm

The outer germ layer formed during gastrulation; gives rise to the nervous system, skin, and hair.

Mesoderm

The middle germ layer formed during gastrulation; gives rise to bone, muscle, blood, and connective tissue.

Endoderm

The inner germ layer formed during gastrulation; gives rise to internal organs such as the stomach and intestines.

Neurulation

The process by which the nervous system forms from the ectoderm during early development.

Neural plate

A flat group of cells derived from ectoderm that begins the process of forming the neural tube.

Neural groove

A depression formed in the neural plate as it begins to fold inward.

Neural tube

A tube formed by the closure of the neural groove; gives rise to the brain and spinal cord.

Neural crest cells

Cells at the edge of the neural tube that migrate and develop into the peripheral nervous system and other tissues.

Neural tube cavity

The hollow center of the neural tube that becomes the brain's ventricles and the spinal cord's central canal.

Neural tube closure

Closure of the neural tube starting in the middle and proceeding toward both the head (rostral) and tail (caudal) ends.

Anencephaly

A fatal condition caused by failure of the rostral neural tube to close, resulting in absence of major brain and skull parts.

Spina bifida

A birth defect caused by failure of the caudal neural tube to close, resulting in incomplete spinal cord development.

Neural Tube Defects (NTDs)

Conditions that result from the neural tube not closing properly during early development.

NTDs - Genetic Component

About 70% of neural tube defects have a genetic component, though folic acid greatly reduces risk.

Folic acid

A vitamin essential for DNA synthesis and repair; deficiency increases risk of neural tube defects.

Folic acid supplementation

The intake of folic acid through diet or supplements to reduce the risk of NTDs.

Folic acid fortification

The U.S. FDA's 1998 mandate to add folic acid to grain products, which led to a 35% drop in NTDs.

Folic acid intake stats

Anencephaly (NTD)

A type of neural tube defect caused by failure of the rostral end to close, leading to brain absence.

Encephalocele

A neural tube defect where brain and meninges protrude through a skull defect.

Hydrocephalus

A condition where cerebrospinal fluid builds up in the brain's ventricles, increasing pressure.

7 Steps of Nervous System Development

The sequential stages: cell proliferation, migration, differentiation, circuit formation, cell death, synaptic pruning, myelination.

Cell proliferation

The process of neural stem cells dividing by mitosis to produce new cells.

Neural stem cells (NSCs)

Cells in the developing nervous system capable of dividing and producing various neural cell types.

Pluripotent stem cells

Stem cells that can give rise to many different cell types.

Oligopotent stem cells

Stem cells that can give rise to a few specific types of cells.

Unipotent stem cells

Stem cells that can only produce one type of cell.

Zika virus

Transmitted by Aedes aegypti mosquito. A virus that, when contracted during pregnancy, can reduce NSC proliferation and cause microcephaly.

Microcephaly

A condition where a baby's brain is significantly smaller due to impaired development.

Migration

The movement of neurons to their correct locations in the developing brain.

Radial glial cells

Cells that guide migrating neurons to their final destinations during brain development.

Cerebral cortex formation

The cortex develops in an inside-out pattern where newer neurons pass older ones.

Lissencephaly

A brain disorder caused by defective migration, resulting in a smooth brain lacking folds and grooves. Causes intellectual disability and developmental delays.

Differentiation

The process by which neurons become specialized into motor, sensory, or interneurons.

Motor neurons

Neurons that transmit signals from the brain/spinal cord to muscles.

Sensory neurons

Neurons that carry signals from sensory receptors to the brain/spinal cord.

Interneurons

Neurons that connect other neurons within the brain and spinal cord.

Sonic Hedgehog

A signaling molecule that promotes motor neuron fate during differentiation.

Bone Morphogenetic Protein (BMP)

A signaling molecule that promotes sensory neuron fate during differentiation.

Circuit formation

The process where axons and dendrites grow and form synaptic connections.

Synaptogenesis

The formation of synapses between neurons during development.

Neuromuscular junction

A synapse between a motor neuron and a muscle fiber.

Cell death (apoptosis)

The programmed elimination of excess or unnecessary neurons during development.

Neurotrophins

Molecules that support neuron survival; neurons compete for them during development.

Synaptic pruning

The elimination of weak or unused synaptic connections to refine neural circuits.

Over-pruning

A condition where too many synapses are removed, associated with schizophrenia.

Under-pruning

A condition where too few synapses are removed, associated with autism spectrum disorder.

Myelination

The process of forming a myelin sheath around axons to speed up signal transmission.

Gestational myelination

Myelination begins around 24 weeks of gestation and continues into adulthood.

Sensory system myelination

Sensory systems are myelinated before motor systems during development.

Environmental effects on myelination

Enriched environments increase myelination; neglect reduces white matter development.

Corpus callosum

A brain structure that can show reduced white matter due to childhood neglect with noticeable effects by age 17.

Neural plasticity

The brain's ability to adapt structurally and functionally in response to experience.

Critical periods

Windows in development when the brain is especially sensitive to environmental input.

Monocular deprivation

A condition that causes permanent visual deficits if during critical period.

Maternal care in rats

Rats with high maternal care develop better stress responses due to brain changes.

Language acquisition

Learning language requires exposure during early childhood.

Birdsong learning

Birds must learn their species' song within about two months after hatching.

Adolescence

A developmental period with major brain refinement and high sensitivity to stress and drugs.

Reward system in adolescence

Develops earlier than the executive system, leading to risk-taking behavior.

Executive system in adolescence

Develops later; responsible for decision-making and impulse control.

Neuroplasticity in adulthood

The adult brain retains the ability to change, but more limited than during early development.

Axonal degeneration

The breakdown of axons due to injury or disease.

Axonal regeneration in CNS

Regeneration is poor due to glial scarring and inhibitory molecules like Nogo.

Nogo

A molecule in the CNS that inhibits axon regeneration.

Axonal regeneration in PNS

Regeneration is more successful with the help of Schwann cells.

Schwann cells

Cells in the PNS that support axon regeneration and myelination.

Transneuronal degeneration

Neuron death that occurs when connected neurons are damaged.

Alzheimer's disease and ALS (transneuronal)

Neurons die and cause degeneration of connected neural circuits.

Cortical map reorganization

The brain's adaptation of functional maps in response to learning, training, or injury.

Juggling study

A study showing increased gray matter in visual areas after learning to juggle.

Stability vs. plasticity

The balance between maintaining brain function and allowing change and learning.

Adult neurogenesis

The process of generating new neurons in the adult brain that supplements existing circuits rather than forming new circuits

Developmental neurogenesis

Widespread formation of neurons that establish entire neural circuits.

Subventricular zone

A region where adult neurogenesis occurs near the lateral ventricles.

Dentate gyrus

A region in the hippocampus where adult neurogenesis takes place.

Neural progenitor-like cells

Immature neurons found in the adult brain, supporting evidence for neurogenesis.

AI and gene expression studies

Modern tools used to detect neurogenesis in adult human brains.

Brain maturation

The brain reaches full maturity around age 25.

Brain aging

After age 45, the brain loses weight, neurons shrink, and synapses decrease.

Pyramidal neuron atrophy

Aging-related shrinkage of a major type of neuron in the brain.

Dopamine receptor loss

Aging leads to fewer dopamine receptors, impacting mood and movement.

Cytoskeletal changes

Structural alterations in neurons seen in aging and neurodegenerative diseases.

Increased glial activity

Glial cells become more active with aging, potentially contributing to inflammation.

Caloric restriction

Has been shown to delay brain aging and reduce Alzheimer's risk.

Alzheimer's Disease (AD)

A progressive neurodegenerative disease characterized by memory loss and cognitive decline.

Neurofibrillary tangles

Twisted fibers inside neurons made of tau protein that disrupt function in Alzheimer's.

Tau protein

A protein that normally stabilizes microtubules; becomes abnormal in Alzheimer's.

Amyloid plaques

Deposits of amyloid-beta protein that accumulate between neurons and cause damage.

Amyloid-beta

A protein fragment that forms toxic plaques in the brains of people with Alzheimer's.

Inflammation in AD

Plaques trigger immune responses that lead to neuron death.

Neuron loss in AD

Widespread death of brain cells that leads to cognitive and functional impairments.

Acetylcholine (ACh)

A neurotransmitter essential for learning and memory; levels drop in Alzheimer's.

Donepezil

A cholinesterase inhibitor drug used to treat Alzheimer's by increasing ACh levels.

Glutamate

A major excitatory neurotransmitter that can cause neuron damage when in excess.

Excitotoxicity

Neuron damage caused by excessive glutamate activity.

Memantine

A drug that blocks NMDA glutamate receptors to reduce excitotoxicity in Alzheimer's.

Aducanumab

An FDA-approved drug (2021) that targets and helps clear amyloid plaques in Alzheimer's.