I always wonder why do one get tears when he is not crying

Basically there are three types tears

• Basal tears (which flow continuously from the lacrimal glands) clean and lubricate the eye, making vision possible.
• Reflex tears clear the eye of irritants produced by, say, onion-slicing.
• Psychic or emotional tears are the complicated ones produced by babies and adults alike.

Why do we get tears in our eyes when we yawn?

At the corner of our eye is a tube leading to the nose, at the top of which is a small container called a lachrymal sac. This sac is full of tears. When we yawn the muscles in our face squeeze this sac and tears spill out from the eyes. This also explains why your nose runs when you cry.

Have you ever wonder... why do you get dreams while sleeping...

when we sleep we get dream's during the peak stage of "deep sleep"
So, what is deep sleep? its the fourth stage in the sleeping cycle.

In the final stage there is process called REM

Rapid eye movement : Rapid eye movement sleep (REM) is the portion of sleep when there are rapid eye movements (REMs).

Dreams occur during REM sleep. We typically have 3 to 5 periods of REM sleep per night. They occur at intervals of 1-2 hours and are quite variable in length. An episode of REM sleep may last 5 minutes or over an hour. About 20% of sleep is REM sleep. If you sleep 7-8 hours a night, perhaps an hour and half of that time, 90 minutes, is REM sleep.

REM sleep is characterized by a number of other features including rapid, low-voltage brain waves detectable on the electroencephalographic (EEG) recording, irregular breathing and heart rate and involuntary muscle jerks.

By contrast, NREM (non-REM) sleep is dreamless sleep. During NREM, the brain waves on the EEG are typically slow and of high voltage, the breathing and heart rate are slow and regular, the blood pressure is low, and the sleeper is relatively still. NREM sleep is divided into 4 stages of increasing depth of sleep leading to REM sleep. About 80% of sleep is NREM sleep. If you sleep 7-8 hours a night, all but maybe an hour and a half is spent in dreamless NREM sleep.

Have you ever noticed we tend to yawn when we see someone else yawn

It might sound like a myth but still.,

What makes you yawn when someone else yawns?

Ha ha... why?? well most answer would be about lack of oxygen to your brain that just like when someone tells you that he/she is hungry, even if you're not, you'll suddenly feel hungry by instinct...

If you don't believe me then try this little Experiment:-

Take a big yawn, cover your mouth out of courtesy, and watch and see how many people yawn. There's a good chance that you'll set off a chain reaction of yawns. Before you finish reading this question of the day, it's likely that you will yawn at least once...

Reason:-

Actually what happens when we cut onion

Actually what happens when we cut onion....

When we cut an onion , it cells broke and release an enzyme which contains sulfenic acid. Sulphenic acid is very unstable it evaporates easily.The evaporated gas reaches our eyes and reacts with water in our eye producing sulfuric acid.This sulfuric acid irritates our eyes.To relieve from this irritation our eyes will start to produce tears.

let see what all other stage of sleep

let see what all other stage of sleep

Stage 1
Stage 1 sleep, or drowsiness, is often described as first in the sequence, especially in models where waking is not included. Polysomnography shows a 50% reduction in activity between wakefulness and stage 1 sleep. The eyes are closed during Stage 1 sleep, but if aroused from it, a person may feel as if he or she has not slept. Stage 1 may last for five to 10 minutes.

Stage 2
Stage 2 is a period of light sleep during which polysomnographic readings show intermittent peaks and valleys, or positive and negative waves. These waves indicate spontaneous periods of muscle tone mixed with periods of muscle relaxation. Muscle tone of this kind can be seen in other stages of sleep as a reaction to auditory stimuli. The heart rate slows, and body temperature decreases. At this point, the body prepares to enter deep sleep.

Stages 3 and 4
These are deep sleep stages, with Stage 4 being more intense than Stage 3. These stages are known as slow-wave, or delta, sleep. During slow-wave sleep, especially during Stage 4, the electromyogram records slow waves of high amplitude, indicating a pattern of deep sleep and rhythmic continuity.