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Psychology & Neuroscience
Neurons and Synapses
How nerve signals travel and cells communicate
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Neurons are specialized cells that carry information through the nervous system and make mental life possible. Every sensation, decision, memory, and emotion depends on patterns of neuron activity. In psychology, neurons help explain how physical events in the brain can influence thoughts and behavior. Understanding their structure shows how information moves from one cell to the next.
Key Facts
- Dendrites receive incoming signals from other neurons.
- The soma, or cell body, integrates signals and supports cell functions.
- Axons carry action potentials away from the soma toward synapses.
- Myelin increases signal speed by insulating the axon and allowing signals to jump between nodes.
- Membrane potential is the voltage difference across the neuron membrane: V_m = V_inside - V_outside.
- Signal speed can be estimated with speed = distance/time.
Vocabulary
- Neuron
- A neuron is a nerve cell that receives, processes, and sends information through electrical and chemical signals.
- Dendrite
- A dendrite is a branch-like part of a neuron that receives signals from other neurons.
- Axon
- An axon is the long fiber of a neuron that carries electrical signals away from the cell body.
- Synapse
- A synapse is the tiny gap where one neuron communicates with another cell using chemical messengers.
- Neurotransmitter
- A neurotransmitter is a chemical released at a synapse that changes the activity of a nearby neuron.
Common Mistakes to Avoid
- Thinking neurons physically touch at synapses. Most synapses have a small gap, so communication often happens when neurotransmitters cross the synaptic cleft.
- Confusing dendrites and axons. Dendrites usually receive signals, while axons usually send signals away from the cell body.
- Assuming stronger stimuli make action potentials larger. Action potentials are all-or-none, so stronger stimuli usually increase firing rate rather than spike size.
- Ignoring inhibitory signals. Neurons do not simply add excitement, because inhibitory inputs can reduce the chance that the neuron fires.
Practice Questions
- 1 A nerve signal travels 0.80 m along a myelinated axon in 0.010 s. Calculate the signal speed using speed = distance/time.
- 2 A neuron has a resting membrane potential of -70 mV and reaches -55 mV at threshold. Calculate the change in membrane potential needed to reach threshold.
- 3 A neuron receives several excitatory inputs and one strong inhibitory input at the same time. Explain how this could affect whether the neuron fires an action potential.