1. Neuron to Neuron Impulse Movement
Since action potentials do not ordinarily cross the synaptic cleft, how does one neuron stimulate the next?

2. “Action” at the Synapses:
How Neurotransmission Works:

3. “Action” at the Synapses
Neurotransmitter is created in the cell body and packaged into vesicles for transport.
The neurotransmitter containing vesicles travel down the axon of the stimulated neuron to the synaptic knob.

4. 3) The Action Potential also travels down the axon carrying the impulse.
4a) When it reaches the synaptic knob, Ca2+ channels open and Ca2+ enters
the neuron.
Ca2+
Ca2+
Ca2+

5. 4b) The presence of the Ca2+ causes the vesicles to be pushed up against
the presynaptic cell membrane, and the neurotransmitter empties into
the synaptic cleft.

6. 5) Neurotransmitter attaches to the receptors on the postsynaptic neuron.
When enough receptor sites are filled sodium channels open and Na+
rushes in.
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+

7. The entry of the positively charged sodium ions causes the beginning of a “new” Action Potential and the impulse carries on. The neurotransmitter then either dissipates or returns to the vesicles in the presynaptic neuron.