During physiological patterns of activity, synaptic activity is regulated by many forms of short-term plasticity. Here, we compare the functional consequences of such plasticity at the synapse from the climbing fibre to the Purkinje cell in the cerebellum and at the synapse between the retinal ganglion cell and the thalamocortical relay neuron in the lateral geniculate nucleus. Despite superficial similarities between these two powerful synapses, they have distinctive synaptic plasticity. The climbing fibre synapse is highly reliable but accomplishes this through many synaptic specializations. However, the retinogeniculate synapse dynamically regulates the flow of visual information by using two types of receptor that have different types of plasticity. These synapses illustrate the important functional consequences of synaptic plasticity.