Procedure 2 Time To Trace

Procedure 2: Time to Trace!

Let’s now trace the entire series of events through a three-neuron loop, including the steps of synaptic transmission between neurons 1 and 2, the propagation of the action potential down the axon of neuron 2, and the steps of synaptic transmission that occur between neuron 2 and 3. Hints are included to ensure that you stay on the right track as you trace.

You may wish to consult your textbook for more details on this process. When you have completed the activity, answer Check Your Understanding questions 5 through 7 (p. 332).

Start: The neuronal action potential reaches the axon terminal of neuron 1 → neurotransmitters are released from the axon terminal by exocytosis, diffuse across the synaptic cleft, and bind to receptors on the postsynaptic membrane of neuron 2, generating an excitatory local potential → if the neuron is stimulated enough times, the excitatory local potentials summate and spread through the neuron’s plasma membrane toward the axon → when the trigger zone is depolarized to threshold, an action potential is generated, which propagates down the axon until it reaches the axon terminals → depolarization of the axon terminal triggers the opening of voltage-gated calcium ion channels, and these ions enter the axon terminal → neurotransmitters are released from the axon terminal by exocytosis → neurotransmitters diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane of

neuron 3, generating an excitatory or inhibitory local potential. End