Synapses are junctions between neurones that allow signals to be transmitted.
Why can nerve impulses only travel in one direction across a synapse?
Neurotransmitter receptors are only present on the post-synaptic membrane, and neurotransmitters are only released from the pre-synaptic neurone.
The electrical impulse can jump across the synaptic cleft in one direction but is blocked in the other direction.
Neurotransmitters are only degraded on the pre-synaptic membrane after binding.
Vesicles containing neurotransmitters are only located in the post-synaptic neurone.