Development of the CNS and Plasticity

Vocabulary flashcards covering major terms related to embryonic CNS development, synaptogenesis, trophic factors, plasticity, pruning, aging changes, and basic synapse types as presented in the lecture notes.

Ectoderm

Outermost embryonic germ layer that gives rise to the nervous system and skin

Neuroectoderm

Specialized ectoderm that forms the neural plate and ultimately the CNS

Neural Plate

Flattened sheet of neuroectodermal tissue that folds to begin CNS formation

Neural Groove

Longitudinal depression in the neural plate that deepens before tube closure

Neural Tube

Hollow structure formed by fusion of neural folds; precursor of brain and spinal cord

Neurulation

Process of forming the neural tube during early embryonic development

Telencephalon

Anterior subdivision of the prosencephalon that becomes the cerebral hemispheres

Diencephalon

Posterior part of the forebrain giving rise to thalamus, hypothalamus, epithalamus

Mesencephalon

Midbrain region between forebrain and hindbrain in the developing neural tube

Rhombencephalon

Hindbrain region that later divides into metencephalon and myelencephalon

Metencephalon

Subdivision of hindbrain forming the pons and cerebellum

Myelencephalon

Caudal hindbrain region that develops into the medulla oblongata

Prosencephalon

Embryonic forebrain comprising telencephalon and diencephalon

Neurogenesis

Generation of new neurons from neural stem or progenitor cells

Neuronal Proliferation

Rapid increase in neuron numbers during early brain growth

Neuronal Migration

Movement of immature neurons to their final cortical or subcortical positions

Glial Proliferation

Increase in number of glial cells to support neurons and enable myelination

Neuronal Differentiation

Process by which neurons acquire specific structural and functional properties

Synaptogenesis

Formation of synaptic connections between neurons or between neuron and muscle

Myelination

Wrapping of axons by glial membranes to speed electrical conduction

Growth Cone

Motile tip of a growing axon or dendrite that explores the environment for guidance cues

Activity-Independent Mechanisms

Genetically programmed developmental events like differentiation and initial axon guidance

Activity-Dependent Mechanisms

Developmental changes requiring neuronal firing, e.g., synaptic modification and pruning

Critical Period

Limited developmental window when specific experiences are required for normal function

Sensitive Period

Optimal time for acquiring a skill; learning later is possible but less efficient

Synaptic Pruning

Elimination of weaker synapses to refine neural circuits

Apoptosis

Programmed cell death that removes unnecessary neurons during development

Large-Scale Stereotyped Axon Pruning

Pruning of entire axon branches that initially reach both correct and incorrect targets

Small-Scale Axon Terminal Arbor Pruning

Local loss of individual terminal branches based on usage (‘use it or lose it’)

Synaptotrophins

Growth factors released from active synapses that stabilize strong connections

Synaptotoxins

Signals thought to be released from postsynaptic cells to repel weak axonal inputs

Neuromuscular Junction (NMJ)

Synapse between a motor neuron and a skeletal muscle fiber

Motor Neuron

Efferent neuron whose axon innervates skeletal muscle

Myofiber

Multinucleated skeletal muscle cell receiving neural input

Schwann Cell

PNS glial cell that myelinates peripheral axons and caps the NMJ

Acetylcholine (ACh)

Neurotransmitter released at NMJs, binding to ACh receptors to trigger muscle contraction

Acetylcholine Receptor (AChR)

Ligand-gated ion channel on muscle membrane that responds to ACh

Trophic Factors

Extracellular proteins that promote neuron survival and growth

Nerve Growth Factor (NGF)

First identified neurotrophin; supports survival of sympathetic and sensory neurons

Brain-Derived Neurotrophic Factor (BDNF)

NGF-related neurotrophin important for CNS neuron survival and plasticity

Ciliary Neurotrophic Factor (CNTF)

Protein that supports motor neuron survival via JAK-STAT signaling

Glial-Derived Neurotrophic Factor (GDNF)

TGF-β family trophic factor essential for dopaminergic and motor neuron survival

Trk Receptor

Receptor tyrosine kinase family binding NGF, BDNF, NT-3/4

JAK-STAT Pathway

Intracellular signaling cascade activated by CNTF and related cytokines

Smad Proteins

Transcription factors phosphorylated downstream of GDNF/TGF-β receptors

Radial Glial Cells

Embryonic glia that serve as scaffolds for migrating neurons

Plasticity

Ability of the nervous system to reorganize structurally and functionally

Hemispherectomy

Surgical removal or disconnection of one cerebral hemisphere, illustrating brain plasticity

Suprachiasmatic Nucleus (SCN)

Hypothalamic ‘master clock’ regulating circadian rhythms and sleep-wake cycles

Slow-Wave Sleep

Deep non-REM sleep stage vital for memory consolidation, reduced with aging

Lipofuscin

Aging-related brown pigment accumulating in neurons

Plaques and Tangles

Protein aggregates associated with neurodegenerative changes, notably Alzheimer’s disease

Axo-Dendritic Synapse

Connection where an axon terminal contacts a dendrite

Axo-Somatic Synapse

Synapse formed directly onto the neuronal cell body

Axo-Axonic Synapse

Synapse between the axon terminal of one neuron and the axon of another

Gate Control Theory of Pain

Model proposing spinal ‘gates’ modulate pain transmission via competing sensory inputs