Neuro 405: Exams Review

Neuro 405: Exams Review Takehome Parts

11. Neuronal Polarity

  • Establishment by Calcium Signaling

    • Neuronal polarity refers to the distinct structural orientation of nerve cells, crucial for proper signal transmission.

    • Key Elements of Polarity:

    • Cytoskeleton: Establishes neuronal polarity, creating a structural framework that differentiates axons and dendrites.

    • Directionality of Microtubules: Microtubules within neurons have a polarity, leading them to facilitate direction of transport and signal transmission.

    • Synaptic Vesicles: Originates from the Golgi apparatus in the soma, where proteins are modified, sorted, and proofread for misfolding.

  • Transportation Mechanism

    • Synaptic vesicle transport depends on motor proteins for movement along microtubules. Kinesin and dynein are involved, moving cargo from the soma to the axon terminal and vice versa.

    • Transport Types:

      • Anterograde Transport: Movement from soma to axon terminal.

      • Retrograde Transport: Movement back from terminal to soma.

12. Selective Fusion and Protein Trafficking

  • Vesicle Fusion and Release Mechanism:

    • Vesicle Docking: Specific vesicles dock with the presynaptic membrane, priming requires calcium influx.

    • Types of Transmitters:

    • Non-Peptide Transmitters: Rapidly released in response to depolarization or action potentials (APs).

    • Peptide Transmitters: Sequestered in dense core vesicles, released in response to stronger signals or repeated stimuli.

  • Calcium Signal Encoding:

    • Different forms of release are dictated by calcium levels.

    • Small, fast release (CVs) vs. slow, sustained release (DCVs), both triggered by varying levels of intracellular calcium.

    • Frequency and Duration of Calcium Signals:

    • Calcium amplitude and frequency can encode different types of information and influence neurotransmitter release dynamics.

13. Stopping Synaptic Transmission

  • Mechanisms to Stop Synaptic Transmission:

    1. Removal of calcium from the synaptic terminal through active calcium pumps leads to cessation of neurotransmitter release.

    2. Transmitter diffusion out of the synaptic cleft.

    3. Reuptake of neurotransmitters back into the presynaptic neuron.

Perineuronal Nets (PNN)

  • Definition and Function:

    • PNNs are extracellular matrix structures surrounding the soma and proximal dendrites, aiding in inhibitory signaling and regulating synaptic plasticity.

    • Role in Drug Abuse:

    • PNNs contribute to the locking of neurotransmitters onto synaptic sites, potentially hindering synaptic plasticity.

GABA Receptors and Neurotransmitter Dynamics

  • Neurotransmission at Different Age Stages:

    • GABA can exhibit excitatory effects in neonatal stages due to ion concentration gradients differing from adults where GABA is primarily inhibitory.

  • Mechanism of Action of GABA:

    • Neurotransmitter binding leads to chloride ion influx, influencing hyperpolarization or depolarization depending on the receptor and cell type.

    • Changes in GABA receptor activity, such as through developmental shifts or location-specific expression, can alter overall excitability and synaptic strength.

Calcium (Ca2+) Signaling

  • Intracellular and Extracellular Calcium Levels:

    • Resting intracellular Ca2+ levels are typically between 10-100 nM, while extracellular levels are around 1.8-2 mM, playing key roles in signaling and cellular functions.

    • Calcium entry mainly via voltage-gated channels and is tightly controlled through active transport mechanisms.

  • Calcium as a Second Messenger:

    • Ca2+ influences various intracellular processes by activating signaling pathways, including the activation of kinases and second messenger formation (cAMP).

Retrograde Signaling and Long-Term Potentiation (LTP)

  • Definition of Retrograde Signals:

    • Molecules, such as nitric oxide (NO), transmitted back to the presynaptic terminal, affecting neurotransmitter release probabilities.

  • Mechanism of LTP Induction:

    • Requires simultaneous activity within a 5 ms window involving calcium signaling, AMPA receptor trafficking, and gene transcription/translation processes.

  • Synaptic Tagging:

    • The process of marking synapses so that they can receive plastic changes purported by activity.

  • Homeostatic Scaling:

    • The adjustment of receptor numbers (like AMPA) in response to activity levels, effectively modulating synaptic strength based on neuron firing rates.