How do impulses cross the synapse?
By means of chemical messenger called neurotransmitters.
- The nerve impulse arrives at presynaptic neuron and starts an action potential in it.
- This action potential can not jump from one neuron to the next neuron.
- So, there must be a mechanism for its transmission. And ofcourse there is an amazing mechanism set by Nature which is Synaptic transmission, which occurs through synapse.
- Synapse is a microscopic gap between axon-ending of presynaptic neuron and dendrite-ending of postsynaptic neuron.
- The pre-synaptic neuron has synaptic vesicles in its synaptic knob.
- These synaptic vesicles are filled with special type of chemical messenger called neurotransmitters, which offer great services in the transmission of the actin potential.
- Thus, the action potential when arrives at the axon-ending of presynaptic neuron , the synaptic vesicles fuse with synaptic membrane. As a result of this fusion, neurotransmitters are released in the synaptic cleft(gap).
- The membranes(of dendrites) of post-synaptic neuron have receptors .
- The neurotransmitters released from the presynaptic neuron binds to the receptors of the postsynaptic neuron.
- These neurotransmitter change the permeability of postsynaptic neuron for certain ions i.e
- Thus, they start an action potential in the postsynaptic neuron.
This is how the two neurons work...
Hope it helps...