Describe the human body response at cell level to perceived starvation threats as when a person is dieting or ill?
When a person is dieting or ill, the body enters a state of perceived starvation. This triggers a complex set of hormonal and metabolic adaptations that help the body conserve energy and maintain essential functions.
1. Hormonal Changes
- Increased Cortisol: In response to perceived starvation, the adrenal glands release the stress hormone cortisol. Cortisol helps mobilize energy stores by stimulating the breakdown of carbohydrates, proteins, and fats. It also suppresses non-essential functions, such as growth and reproduction, to divert resources to essential processes.
- Decreased Insulin: Insulin is a hormone that helps cells absorb glucose from the bloodstream for energy. During periods of perceived starvation, insulin levels decrease to reduce the uptake of glucose by cells. This allows the body to conserve glucose for vital organs, such as the brain and heart, and promote the use of alternative fuel sources, such as stored fats.
- Increased Glucagon: Glucagon is a hormone that stimulates the liver to produce glucose from stored glycogen. During perceived starvation, glucagon levels increase to support glucose production and maintain blood glucose levels within a normal range.
2. Metabolic Adaptations
- Increased Lipolysis: Lipolysis is the process of breaking down triglycerides (stored fats) into glycerol and fatty acids. When the body perceives a lack of energy, it increases lipolysis to release fatty acids into the bloodstream. These fatty acids can be used as an alternative fuel source by cells throughout the body.
- Ketosis: If perceived starvation persists, the body may enter a state of ketosis. During ketosis, the liver converts fatty acids into ketone bodies, which can be used as an energy source by the brain and other tissues. Ketosis can lead to changes in mood, appetite, and energy levels.
- Reduced Metabolic Rate: To conserve energy, the body may lower its metabolic rate by slowing down non-essential processes. This can result in a decrease in body temperature, heart rate, and breathing rate.
- Protein Catabolism: In extreme cases of starvation, the body may break down muscle tissue to release amino acids for energy. This process, known as protein catabolism, can lead to muscle loss and weakness.
Overall, the body's response to perceived starvation involves a coordinated series of hormonal and metabolic adaptations that help maintain essential functions, conserve energy, and preserve vital tissues. These adaptations are essential for survival during periods of limited food availability or increased energy demands, but they can also have adverse effects on overall health if prolonged or extreme.