Review the steps of an action potential and the events at synapses, and then fill in the following blanks, as you trace the events in a 3-neuron sequence, including the generation and propagation of the action potentials, and the synaptic events between the neurons.

Neuronal action potential reaches the axon terminal of neuron 1, which causes _______________ to open, leading to an influx of calcium into the axon terminal of Neuron # 1. This causes the exocytosis of vesicles filled with _________________ that leave the ______________ of neuron # 1 and diffuse across the synaptic cleft to Neuron # 2. At Neuron # 2, neurotransmitters bind to the postsynaptic membrane of neuron #2 and generate an excitatory/depolarizing local potential by opening_____________. This excitatory depolarization spreads through neuron # 2 from the ____________________to the________________ and finally to the _______________, where the axon hillock is depolarized to threshold by the summation of the local potentials. Depolarization of the axon hillock causes ________________ to open, which allows _______________ to rush into the axon, causing an ___________________. The action potential is propagated down the axon of neuron # 2 via ____________________ because neuron # 2 is a myelinated motor neuron. After the action potential passes, ______________________open and ___________________ exits the neuron, causing repolarization of that part of the neuronal membrane. The action potential continues to propogate down the axon of neuron # 2 until it reaches the ______________________ of neuron # 2 and causes the opening of _____________________. Calcium influxes into the axon terminal and causes the release of __________________, which diffuse across the _______________________ between neuron # 2, which is the ____________________neuron, and neuron # 3, which is the ________________ neuron. Neurotransmitters cause excitatory/depolarizing or inhibitory/hyperpolarizing local potentials in the postsynaptic membrane of neuron # 3.

 

Choose from the following possible terms – not all may be used and some may be used more than once: 

Axon terminal, sodium voltage-gated channels, calcium voltage-gated channels, potassium voltage-gated channels, axon hillock, neurotransmitters, sodium, calcium, potassium, dendrites, soma, action potential, saltatory conduction, continuous conduction, synaptic cleft, postsynaptic, presynaptic.

n cell body synapse #2 Neuron #3 nucleus axon of previous neuron neuron cell body cleus dendrites of axon next neuron tips electrical signal synpse #1 Neuron #1 Neuron #2 dendrites