Why do you have tears when you doze off? Why do people cry when they are sleepy and dozing off?

Sleep is a normal physiological phenomenon, when people are tired, breathing gradually changes from deep and fast to shallow and slow, so that the oxygen content in the blood decreases, and the brain and other important organs are in a state of relative ischemia and hypoxia; The respiratory center in the brain, which is responsible for breathing, will send a signal to take a deep breath, which is manifested as a yawn, so that the intake of oxygen can be appropriately increased to relieve brain fatigue.

Tears do not exactly indicate a change in mood. For example, when a foreign object such as dust falls into our eyes, a large number of tears are generated and the foreign body is washed out.

In addition to a large amount of water, there are lysozyme, immunoglobulin, complement system, lactoferrin, -lysin, etc., which have the effect of inhibiting the growth of bacteria and keeping the eyeball moist,。。 These two autonomic-controlled self-regulatory functions of the body may be linked in some people. Therefore, it is normal to shed tears when yawning.

When I'm sleepy, I always yawn. When you yawn, your eyes will always be full of tears, why do people shed tears when they yawn? Human tears are secreted all the time, flowing on the surface of the eyeball.

However, there is very little tears secreted and they flow along the surface of the eyeball and in the tiny spaces inside the eyelids, so you don't feel that the tears are flowing. However, in the blink of an eye, the tears on the surface of these eyeballs are sucked into the nasolacrimal duct, the sewer of the tears. Don't underestimate this not-so-long tube, it's the only way for tears to reach your nose.

The lacrimal glands constantly secrete tears, and the nasolacrimal ducts constantly excrete tears, so people usually do not shed tears. When a person yawns, his mouth is wide open, and he may exhale more than he can out of his body in order to exhale carbon dioxide and inhale oxygen. With the action of yawning, a stream of gas exhales forcefully from the mouth.

The muscles of the cheeks, tongue and throat tense and contract, and the pressure in the mouth and nose increases. As a result of the increased pressure in the nasal cavity, it will temporarily block the work of the nasolacrimal duct to excrete tears, and the "sewer" will not be passed, and the tears will not flow, and more and more tears will accumulate in the eyes. There will be tears in his eyes, and finally he will burst out of his eyes and flow to his face.

In fact, not only yawning can cause tears, but also when people laugh, sneeze, cough, and vomit, and the reason is the same.

Why do people shed tears when they yawn?

That could be if you have a cold and see a doctor.