Neuron and Neurotransmitter

Which part of the neuron is primarily responsible for integrating incoming synaptic signals and initiating an action potential if the threshold is reached?

• Dendrites

• Axon hillock

• Axon terminal

• Nodes of Ranvier

Which ion is most responsible for the depolarization phase of a neuronal action potential?

• Potassium (K⁺)

• Calcium (Ca²⁺)

• Sodium (Na⁺)

• Magnesium (Mg²⁺)

Which of the following best describes the role of the myelin sheath in neuronal transmission?

• It facilitates neurotransmitter release at synapses

• It increases the capacitance of the axonal membrane

• It allows for saltatory conduction, speeding up action potential propagation

• It increases resistance across the membrane, slowing signal propagation

Which neurotransmitter is primarily inhibitory in the adult central nervous system and acts by increasing chloride ion influx?

• Glutamate

• Acetylcholine

• Dopamine

• GABA

Which of the following best explains how neurotransmitters are removed from the synaptic cleft to terminate the signal?

• Only by enzymatic degradation

• Only by diffusion out of the cleft

• By active transport into glial cells only

• By a combination of enzymatic degradation, diffusion, and reuptake into the presynaptic neuron

During the repolarization phase of an action potential, which of the following events occurs?

• Voltage-gated sodium channels open

• Potassium ions exit the neuron

• Calcium ions enter the neuron

• Sodium-potassium pump inactivates