2.3 Flashcards
(10 cards)
- What is axon guidance and why is it critical in neural development?
Axon guidance is the process by which axonal growth cones navigate through the developing nervous system to reach their appropriate targets. This navigation is driven by successive turning decisions in response to external cues, ensuring that neurons form proper connections essential for functional neural circuits.
- What role do growth cones play in axon guidance?
Growth cones are dynamic structures at the tip of extending axons. They detect and integrate environmental signals—such as chemical gradients and cell-adhesion molecules—to steer the axon in the correct direction, ultimately determining the pattern and specificity of neural wiring.
- Which types of cues influence axonal navigation during development?
Axonal navigation is influenced by a variety of guidance cues, including diffusible molecules (e.g., netrins, semaphorins, Slits) and substrate-bound signals (e.g., extracellular matrix components). These cues provide both attractive and repulsive signals that help axons chart their course toward their target regions.
- What is synaptic refinement and how does it shape neural circuits?
Synaptic refinement is the process by which initially exuberant, overabundant synaptic connections are pruned and fine-tuned. During development, activity-dependent mechanisms eliminate weaker or unused synapses while strengthening active connections, resulting in more efficient and specific neural circuits.
- How do activity patterns contribute to the process of synaptic refinement?
Neural activity plays a central role in synaptic refinement. When certain synapses are frequently activated, they are stabilized and may even expand, while inactive or less active synapses are pruned away. This competitive process ensures that the strongest and most relevant connections are maintained to support optimal brain function.
- What happens during the maturation phase of neural development?
Maturation involves several key processes including synaptogenesis (formation of new synapses), myelination (insulation of axons for faster signal transmission), and the selective pruning of synapses. These changes, which continue well into postnatal life, lead to the functional specialization and efficiency of neural circuits.
- How does the timing of synaptic refinement differ between brain regions?
Different brain regions have distinct timelines for synaptic refinement. For example, the visual cortex typically undergoes rapid pruning early in life to adapt to sensory inputs, while regions such as the prefrontal cortex refine synapses over a more extended period, correlating with the slower maturation of higher cognitive functions.
- What structural and functional changes occur in the brain during normal aging?
Normal aging is characterized by a gradual decline in brain volume (about 5% per decade after age 40, accelerating after age 70), loss of grey and white matter, decreased neurotransmitter levels, and reduced myelination. These changes can lead to slower processing speeds, memory and executive function declines, and diminished sensory perception.
- What are some cellular and molecular factors that contribute to brain aging?
Brain aging is influenced by factors such as reduced blood flow, hormonal changes, mitochondrial dysfunction, and the accumulation of toxic or misfolded proteins. Genetics, as well as lifestyle factors, also play a role in the rate and extent of neural aging.
- Which lifestyle factors can help mitigate the effects of brain aging?
Lifestyle factors that can help slow brain aging include regular physical exercise, a balanced diet rich in nutrients, sufficient sleep, low levels of stress, social interaction, and continuous cognitive challenges (like puzzles or learning new skills). These factors contribute to cognitive reserve and promote overall brain health.
