Synapse
The gap between two neurons. When the signal arrives, calcium enters the sending cell and vesicles release neurotransmitter, which crosses the gap and binds receptors on the next cell, starting a new signal.
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Analogy
A relay handoff: the baton changes form to cross the gap.
In practice
Acetylcholine passes the signal from a motor neuron to a muscle. Anaesthetics and many drugs work by changing synapses.
Practice
Flashcards
- What is released into the synapse?Neurotransmitter from vesicles in the sending cell.
Interview questions
- Describe how a nerve impulse travels along a neuron and across a synapse.
- Resting potential
- Sodium in, depolarisation
- Potassium out, repolarisation
- Calcium triggers neurotransmitter release
- Receptors on the next cell
Questions people ask
How are neurotransmitters removed from the synapse?
If the neurotransmitter stayed, the next cell would keep firing. It is removed by enzymes that break it down, like acetylcholinesterase, or by transporters that take it back into the sending cell. Many drugs, such as some antidepressants, work by blocking this removal.
What is the difference between excitatory and inhibitory synapses?
Excitatory synapses make the next neuron more likely to fire, by letting positive ions in. Inhibitory synapses make it less likely, often by letting negative chloride ions in. A neuron adds up all the excitatory and inhibitory input it receives, and fires only if the total passes a threshold.