- A nerve impulse travels down an axon of a nerve until it reaches the terminal branches of the axon. The signal then passes from one neuron to the next across a synapse to the dendrite of the next neuron.

- As the nerve impulse reaches the presynaptic terminal, the action potential triggers an influx of Ca+2. This Ca+2 influx causes synaptic vesicles to fuse with the presynaptic terminal and release their contents (neurotransmitters) into the synapse.

- Neurotransmitters bind to protein receptors on the postsynaptic membrane. The bound receptors open ion channels, allowing ions to pass through. The influx of ions into the neuron changes its membrane potential, either depolarizing (excitatory signal) or hyperpolarizing (inhibitory signal) the cell. When the membrane potential reaches the threshold potential, an action potential will be triggered. Neurotransmitters are then quickly degraded causing ion channels to close.

Drugs that mimic a natural stimulatory neurotransmitter have the effect of

- stimulating the neurons that respond to the neurotransmitter being mimicked by binding to receptor sites.

Neurotransmitters enter the synaptic cleft by

- exocytosis triggered by a rise in cytoplasmic Ca2+ concentrations.

The action potential in the postsynaptic cell is initiated by

- binding of the neurotransmitter to specific receptor proteins causing ion channels to open and allow the influx of specific ions into the cell.

The communication of action potentials from the presynaptic cell to the postsynaptic cell involves the following progression of signals in vertebrates:

- electrical → chemical → electrical

A neuron may release a neurotransmitter that can stimulate or ________ an impulse in the ______________.

- inhibit, post-synaptic neuron

12.14.3 Human Regulation: Synaptic Events: Cell-Cell Communication Flashcards by Irina Soloshenko

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12.14.3 Human Regulation: Synaptic Events: Cell-Cell Communication Flashcards

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