Generally, when people are in a stable mood, pupil dilation and contraction are mainly to control the number of light sources entering the eyes. For example, when the sun is strong, the pupil sphincter will play a role, which will shrink our pupils and reduce the direct stimulation from the sun. When the surrounding light is dim, the mydriatic muscle will control our pupils to enlarge, so as to absorb more light sources and let us see things around us clearly. The sympathetic nerve and parasympathetic nerve, which control the sphincter of pupil and the dilating muscle of pupil, act through the signals processed by our brain.
After being frightened, people instinctively want to maintain the balance of various functions, and at the same time stimulate more energy to speed up our reaction, so as to make a correct response to possible dangers.
When we are frightened, we will first secrete a lot of adrenaline, which will speed up our blood flow and provide more energy for our body. Of course, this rapid hormone supplement will also have some side effects, such as rapid heartbeat and scalp numbness, etc. These are external manifestations, while internal ones are the most exciting to our nervous system.
Sympathetic nerve is mainly influenced by human emotional fluctuations, so when people are excited or afraid, they react first. Through the stimulation of hormones, the sympathetic nerve runs at a high speed, which will first cause our pupils to enlarge. These are relatively normal reactions.
Pupil dilation is not a wrong decision made by our sympathetic nerves in a panic, but a very effective self-protection mechanism. People will feel that their lives are threatened when they are afraid, so they need to get the information around them to the maximum extent in order to find a solution. The most direct way for us to get information is to look through our eyes. When the pupils are dilated, more light sources enter our eyes. We can see farther and wider than usual, and even find some subtle details, which can help us find ways to deal with the current emergency in the shortest time.
However, not all people can respond correctly in a state of fear. Although our bodies feed back a lot of information, some organs of our bodies can't withstand such high-speed operation. For example, in a state of fear or tension, the heart beats too fast, and the brain is rapidly congested, which may cause the rupture of cardiovascular and cerebrovascular diseases. Or our brains will make some wrong decisions when they are nervous, which makes the parties seem a little flustered. This is mainly because our brains can't make a correct judgment based on past experience when they have not experienced such a thing, and people who are not good at thinking at ordinary times or are cautious in character will have a state of brain crash because of the sudden increase in data, which is called being scared silly, which will be even more dangerous.
Pupil dilation is the instinct of the body when frightened, and it is a very important function preserved in the process of evolution. However, because human beings have been in a comfortable state for a long time, many people have lost their ability to use this function, but they can all be restored with proper exercise, which can provide us with more help in an emergency.