Much is often made of the definitive connection between biological and artificial neural networks. 1 Popular publications propagate the idea that ANNs are somehow an exact replica of what's going on in the human (or other biological) brain. This is clearly inaccurate; at best, early artificial neural networks were inspired by biology. The abstract relationship between the 2 are no more definitive than the abstract comparison drawn between the make up and functionality of atoms and the solar system.
The major components of the biological neuron of interest to us are:
The nucleus holds genetic information (i.e. DNA)
The cell body processes input activations and converts them to output activations
Dendrites receive activations from other neurons
Axons transmit activations to other neurons
The axon endings, along with neighboring dendrites, form the synapses between neurons
Chemicals called neurotransmitters then diffuse across the synaptic cleft between an axon ending and a neighboring dendrite, constituting a neurotransmission. The essential operation of the neuron is that an activation flows into a neuron via a dendrite, is processed, and is then retransmitted out an axon, through its axon endings, where it crosses the synaptic cleft, and reaches a number of receiving neurons’ dendrites, where the process is repeated.
Matthew, Mayo. “Deep Learning Key Terms, Explained.” KDnuggets, KDnuggets, 10AD, 2016, http://www.kdnuggets.com/2016/10/deep-learning-key-terms-explained.html (1)