What happens to our bodies when we sleep?

Heart rate

During Stage 1, the heart rate begins to slow, and by Stage 3, it has slowed to its lowest rate. The pulse, on the other hand, quickens to approximately the same pace as while you're awake during REM sleep.

Breathing

Breathing slows down during non-REM sleep, with the lowest rates of respiration occurring during deep sleep stage three. During REM sleep, breathing becomes more rapid and irregular.

Hormone levels

Sleep and the body's internal clock, or circadian rhythm, are crucial in regulating the synthesis of a variety of hormones including:

• Melatonin is a hormone that  induces sleep.

• Growth hormone that promotes bone and muscular growth as well as metabolism.
• Cortisol, which is part of the body’s stress response system
• Leptin and ghrelin, which help control appetite

Muscles

During each stage of non-REM sleep, muscles progressively relax, and the body's overall energy requirement decreases. Most muscles are paralysed during the REM stage, a condition known as atonia. This prevents the legs and arms from flailing in response to the content of the dream. However, the respiratory and ocular muscles remain active, and rapid eye movement sleep gets its name from the darting of the eyes beneath closed eyelids.

Emotional well-being

Sleep is also crucial for emotional well-being. Brain activity in areas that regulate emotion rises during sleep, promoting optimal brain function and emotional stability.

Areas of the brain in which sleep increases activity include:

• amygdala
• striatum
• hippocampus
• insula
• medial prefrontal cortex

The amygdala is one example of how sleep can assist regulate emotion. The fear response is controlled by this area of the brain, which is located in the temporal lobe. It's what regulates your response to a perceived threat, such as a stressful circumstance.

The amygdala can respond in a more adaptive manner when you receive enough sleep. On the other hand, it is more inclined to overreact if you're sleep deprived.

Weight management

Sleep has an impact on your weight by regulating hunger hormones. Ghrelin, which promotes hunger, and leptin, which improves the feeling of being full after eating, are two of these hormones. Ghrelin levels drop during sleep because you utilise less energy than when you're awake.

Sleep deprivation, on the other hand, raises ghrelin while suppressing leptin. This imbalance makes you hungry, which increases your chances of overeating and gaining weight.

Insulin function

Insulin is a hormone that aids in the utilisation of glucose (sugar) by your cells. Insulin resistance, on the other hand, occurs when your cells do not respond to insulin adequately. High blood glucose levels and, eventually, type 2 diabetes can result from this.

Insulin resistance may be aided by sleep. It maintains your cells healthy so they can absorb glucose easily.

During sleep, the brain utilises less glucose, which helps the body control overall blood glucose levels.

What happens when you miss too much sleep?

If you've ever pulled an all-nighter, you know that missing one night of sleep isn't catastrophic. The next day, a person will be irritable and will either slow down (get tired easily) or will be extremely wired due to adrenaline.

However, it grows harsher if a person skips two nights of sleep. Concentration is challenging, and attention spans are dwindling. The number of errors rises.

After three days, a person will begin to hallucinate and will be unable to think clearly.