Knowledge Point 01: Yawning Occurs Due to Excess Carbon Dioxide in the Body to Balance Oxygen Levels
When we feel tired, the amount of carbon dioxide in our bodies increases. To balance the body’s needs, it initiates a deep breathing action—yawning, to inhale more oxygen and expel carbon dioxide, achieving the effect of eliminating fatigue.
Detailed Explanation:
In daily life, after engaging in prolonged physical or mental activities, we often feel tired, and at this point, a large amount of carbon dioxide has accumulated in our bodies. To balance the oxygen and carbon dioxide levels in the body, it regulates through yawning, a natural deep breathing action.
During yawning, we inhale more oxygen than usual and expel carbon dioxide from the body, thereby alleviating physical fatigue. Therefore, yawning is actually the body telling us that it needs more oxygen to regain energy.
Knowledge Point 02: The Gurgling Sound in the Stomach When Hungry is Due to Gastric Juice Secretion and Stomach Contraction
When hungry, the food previously ingested has been digested, but gastric juice continues to be secreted, leading to stomach contraction and expansion, with internal liquids and gases churning to produce a gurgling sound. This is a normal physiological response.
Detailed Explanation:
When we are hungry, we often hear a gurgling sound in our stomachs. This is because the food we previously ingested has been digested, but gastric juice in the stomach continues to be secreted.
At this point, the stomach gradually contracts and expands due to the lack of food, causing the internal liquids and gases to churn, producing the gurgling sound. This is a normal physiological response that tells us the body needs to ingest new food to replenish energy and nutrients.
Knowledge Point 03: We Don’t Feel Itchy When Scratching Ourselves Because the Brain Has Sent a Safety Signal
When scratching ourselves, the brain has already anticipated no danger, causing the nerves to relax, so we don’t feel itchy or laugh; whereas when scratched by someone else, an itchy sensation arises due to unknown factors.
Detailed Explanation:
In daily life, we may find that when scratching ourselves, we often don’t feel very itchy or laugh. This is because when our hands touch our skin, the brain has already anticipated that it is a safe action, so the nerves relax and do not produce a strong itchy sensation.
However, when scratched by someone else, since we cannot predict the other person’s movements and force, the brain generates unknown factors, causing us to feel itchy or laugh.
Knowledge Point 04: Goosebumps Form Due to Nervous Stimulation Causing Piloerection
When the skin is stimulated by nerves (such as anger, fear, or cold exposure), the piloerector muscles contract, causing the hairs to stand up and form goosebumps, which serve the purposes of heat retention and intimidating enemies.
Detailed Explanation:
In certain situations, such as anger, fear, or cold exposure, we may develop goosebumps on our skin. This is because when the skin is stimulated by nerves, the piloerector muscles located below the hair follicles contract and cause the hairs to stand up, forming goosebumps.
This physiological response not only helps maintain body temperature and prevent excessive heat loss but also makes animals look larger than they actually are, thereby intimidating enemies. In daily life, we can observe this phenomenon and better understand the physiological mechanisms of the body.
