The basic process of neuronal activity is reflex, and the basic process of reflex is that the reflex arc consists of five parts: receptors, afferent nerves, interneurons, efferent nerves, and effectors. Reflexes can only be completed if the reflex arc is intact. It can be divided into monosynaptic reflex and polysynaptic reflex. 1. Monosynaptic reflex: between the afferent neuron and efferent neuron, the reflex that passes through only one synapse in the center is called monosynaptic reflex, and tendon reflex is the only reflex in the body that can be completed by monosynaptic reflex only. 2. Multi-synaptic reflexes: Reflexes that pass through multiple synapses in the center are called multi-synaptic reflexes. Most of the reflexes in human beings and higher animals belong to multisynaptic reflexes. They are summarized as follows. (1) Unilinear contact: Unilinear contact means that a presynaptic neuron makes synaptic contact with only one postsynaptic neuron, for example, the contact of the retinal optic cone system. Lower synaptic contacts are also commonly considered to be unilinear contacts. (2) Spoke and convergent contacts: A spoke contact is a neuron that forms synaptic contacts with multiple neurons through its axonal lateral or terminal branches, which is more common in afferent pathways. Convergent connections are those in which a neuron receives projections from the axon terminals of many neurons and establishes synaptic connections, which are more common in efferent pathways. (3) Chain link and ring link: In the neural pathway, if the intermediate neuron constitutes the spokes and the convergent link exists at the same time, then it can form the chain link or the ring link, and the nerve impulse can expand the spatial range of action through the chain link.