Answer to Question 1
Answer: Stage 1 is the lightest stage of sleep. It lasts only a few minutes. Stage 2 lasts 5-15 minutes and is deeper than stage 1. Stages 3 and 4 are delta-wave sleep. Blood pressure, heart rate, and respiration slow. These are the deepest stages. Growth hormone is released during stage 4, and sometimes people sleepwalk, cook, clean, or even drive in this stage, particularly if they are taking sleep medications.
Answer to Question 2
Answer: Sleep deficiency affects the immune system, leaving a person more at risk for viruses and other ailments, along with an overall disruption of immune functioning. It increases the risk of high blood pressure and cardiovascular disease. It also slows down the metabolism and raises the risk of overweight and obesity, and possibly the development of type 2 diabetes. Sleep is also important for neurological functioning, motor tasks, including driving, and stress management.
Stages of Liver Damage
Sleep in a Dolphin
Algorithm for assessing/screening sleep disorders in adults.
A participant in a sleep experiment.
Determination of the number of theoretical stages
The cell cycle has three stages: interphase, mitosis, and cytokinesis