1. How Biology Affects Behaviour

The amount of sleep a person gets can also affect their behaviour, because it has a direct effect on some parts of our physical body.

Benefits of Sleep:

• Learning and memory - Sleep helps the brain commit new information to memory through a process called memory consolidation. In studies, people who had slept after learning a task did better on tests later.
  
  
• Metabolism and weight - Chronic sleep deprivation may cause weight gain by affecting the way our bodies process and store carbohydrates, and by altering levels of hormones that affect our appetite. 
  
  
• Safety - Sleep debt contributes to a greater tendency to fall asleep during the daytime. These lapses may cause falls and mistakes such as medical errors, air traffic mishaps, and road accidents. 
  
  
• Mood - Sleep loss may result in irritability, impatience, inability to concentrate, and moodiness. Too little sleep can also leave you too tired to do the things you like to do.
  
  
• Cardiovascular health - Serious sleep disorders have been linked to hypertension, increased stress hormone levels, and irregular heartbeat. 
  
  
• Disease - Sleep deprivation alters immune function, including the activity of the body’s killer cells. Keeping up with sleep may also help fight cancer.

From Harvard Health Publications -https://www.health.harvard.edu/press_releases/importance_of_sleep_and_health.htm