Q: What is a synapse?
A: A specialized junction where a neuron communicates with another cell (neuron, muscle, or gland) through either chemical or electrical means.
Q: What are the two main types of synapses?
A: Chemical synapses (neurotransmitter-mediated) and electrical synapses (gap-junction-mediated).
Q: What are the advantages and limitations of electrical synapses?
A: Advantages – fast, synchronous activity; Limitations – lack of signal modulation or amplification.
Q: How do chemical synapses transmit signals?
A: Neurotransmitters are released from the presynaptic terminal into the synaptic cleft, binding to receptors on the postsynaptic membrane.
Q: What are the basic steps of chemical neurotransmission?
A: (1) Synthesis/storage, (2) AP-induced Ca²⁺ influx, (3) Vesicle fusion/release, (4) Receptor binding, (5) Termination (reuptake/degradation).
Q: What structural features define a chemical synapse?
A: Presynaptic vesicles, active zones, a synaptic cleft, and postsynaptic receptor densities (e.g., PSD).
Q: What triggers neurotransmitter release at the presynaptic terminal?
A: Opening of voltage-gated Ca²⁺ channels and Ca²⁺ influx in response to an arriving action potential.
Q: Which protein complex mediates synaptic vesicle fusion?
A: The SNARE complex (syntaxin, synaptobrevin/VAMP, SNAP-25) assisted by synaptotagmin (Ca²⁺ sensor).
Q: What are the main mechanisms for terminating neurotransmitter action?
A: Enzymatic degradation, reuptake by transporters, or diffusion away from the cleft.
Q: What are small-molecule neurotransmitters and where are they synthesized?
A: Classical transmitters like ACh, dopamine, glutamate, etc.; synthesized in the presynaptic terminal.
Q: What are peptide neurotransmitters and how are they synthesized?
A: Neuropeptides made in the soma, packaged in dense-core vesicles, and transported to terminals.
Q: What are the four major activating (modulatory) systems of the brain?
A: Cholinergic, Dopaminergic, Noradrenergic, and Serotonergic systems.
Q: What roles does acetylcholine play in the CNS and PNS?
A: CNS – arousal, attention, memory; PNS – neuromuscular junction activation of skeletal muscle.
- Q: Where are dopaminergic cell bodies located and what are their pathways?
A: Substantia nigra (motor control) and ventral tegmental area (reward/motivation).
Q: Which disorder results from degeneration of nigrostriatal dopamine neurons?
A: Parkinson’s disease.
Q: What is the primary function of the noradrenergic system?
A: Modulates alertness, attention, and stress responses via projections from the locus coeruleus.
Q: What is the serotonergic system’s major role and origin?
A: Mood, sleep, appetite regulation; neurons originate in the raphe nuclei of the brainstem.
- Q: Which neurotransmitter is the main excitatory transmitter in the CNS?
A: Glutamate.
Q: Which neurotransmitter is the principal inhibitory transmitter in the brain?
A: GABA (γ-aminobutyric acid).
Q: How do ionotropic receptors differ from metabotropic receptors?
A: Ionotropic = ligand-gated ion channels causing fast EPSPs/IPSPs; Metabotropic = G-protein-coupled receptors producing slower, modulatory effects.
- Q: How can a neurotransmitter produce different effects in different tissues?
A: By acting on distinct receptor subtypes that open or close different ion channels or activate different signaling cascades.
Q: What determines whether a synapse is excitatory or inhibitory?
A: The type of receptor and the ion conductances it controls, not the neurotransmitter itself.
Q: What is a neuromuscular junction (NMJ)?
A: A specialized chemical synapse between a motor neuron and skeletal muscle fiber where ACh triggers muscle contraction.
Q: What is synaptic plasticity?
A: The ability of synapses to strengthen or weaken in response to activity, forming the basis of learning and memory.
