Biological Psychology: Neurons and Action Potentials — Neuron Structure and Cell Types
How a neuron is built, the main shapes and functional classes of neurons, and the glial cells that support them.
Try 3 questions
1. Which part of a typical neuron receives most of the incoming signals from other neurons?
- The myelin sheath
- The axon terminals
- The dendrites
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Answer: The dendrites
Dendrites are branched extensions studded with neurotransmitter receptors, and most synapses onto a neuron form on them.
2. In a typical neuron, where is the action potential usually first triggered?
- Inside the cell nucleus
- At the tips of the dendrites
- At the axon's initial segment
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Answer: At the axon's initial segment
The axon initial segment, next to the axon hillock, has the highest density of voltage-gated sodium channels, so it reaches threshold first.
3. A neuron receives many small excitatory inputs at once, each too weak alone. What decides whether it fires?
- Whether their combined effect reaches threshold
- Whether one input eventually grows strong enough
- Whether all inputs land on one dendrite
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Answer: Whether their combined effect reaches threshold
Neurons sum their inputs across space and time; firing depends on the net depolarization reaching threshold at the axon, not on any single synapse.
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