The basic mode of neuromodulation is reflexes, and the structural basis for completing reflexes is the reflex arc. The reflex arc usually consists of receptors, afferent nerves, nerve centers, efferent nerves, and effectors (efferent nerve endings and the muscles or glands it innervates, etc.).
The excitation of the receptors is transmitted along the afferent nerve to the nerve center; the nerve center then generates excitement and analyzes and synthesizes the afferent information; the excitement of the nerve center passes through a certain efferent nerve to reach the effector; the effector responds to the stimulus. This is the general process of reflection.
So the transfer of excitement in the reflective arc is unidirectional, along the receptor towards the effector. Can judge the afferent nerve and efferent nerve can know the direction of excitement transmission, let the editor and the robot together to summarize the afferent nerve and efferent nerve judgment method.
1. The afferent nerve is linked to the receptor, and the efferent nerve is linked to the effector
ai: In general, it is difficult to judge receptors and effectors in the title, so this method, pass.
2． Depending on whether there is a ganglion: It is the afferent neuron that has the ganglion. C in the figure below is the ganglion, so b in the following figure is the afferent nerve and e is the efferent nerve.
ai: I know, just look at that little pimple, there is a small pimple is the afferent nerve, remember.
3． Judging by synaptic structure: the direction of transmission of excitement between synapses is the axon of one neuron to the cell body or dendrite of another neuron.
Therefore, synapses are divided into axon cell types and axon dendrite types.
Axons to cell bodies or axons to dendrites are introduced to the efferent direction. So b is the afferent nerve and e is the efferent nerve.
AI: It's backwards based on the direction of the excitement transmission.
4． Judging by the structure of the polio, efferent neurons are connected to most of the bulge (anterior horn), and afferent neurons are connected to the narrow part (posterior horn).
ai: Narrow in and wide out, just like the Chinese examination university, strict (narrow) in and wide out.
5. Position of synaptic vesicles
In the known synaptic structure, according to the location of synaptic vesicles, the presynaptic membrane and the postsynaptic membrane can be judged, and the direction of excitation transmission can be judged.
ai: The excitement in the picture above is passed down from above.
6． Cutting experiment method: If a nerve is cut off, the peripheral segment is stimulated (far from the center), the muscle does not contract, and the stimulation is to the middle segment (near the center), and the muscle contracts, then the afferent neuron is cut off, and vice versa, it is the efferent neuron.
ai: The experimental method is too bloody.