These structures branch out in treelike fashion and serve as the main apparatus for receiving signals from other nerve cells. They function as an "antennae" of the neuron and are covered by thousands of synapses. The dendritic membrane under the synapse (the post-synaptic membrane) has many specialized protein molecules called receptors that detect the neurotransmitters in the synaptic cleft. A nerve cell can have many dendrites which branch many times, their surface is irregular and covered in dendritic spines which are where the synaptic input connections are made.