Physiology & Homeostasis Essentials PAST PAPERS CH#1 GUYTON скачать в хорошем качестве

Physiology & Homeostasis Essentials PAST PAPERS CH#1 GUYTON

The human body survives by maintaining a stable internal environment, a process called Homeostasis. This stability is mainly maintained in the Extracellular Fluid, which surrounds and nourishes all body cells. Cells depend on this fluid for oxygen, nutrients, and removal of waste products. Several body systems work together to protect and regulate this internal environment. The Immune System protects the body from pathogens such as bacteria, viruses, parasites, and fungi. It includes white blood cells, lymphocytes, lymph nodes, and the thymus. These components identify foreign substances and destroy them through processes like phagocytosis or by producing antibodies. The Integumentary System, mainly the skin, acts as the first physical barrier against external harm. It also helps regulate body temperature, excrete small amounts of waste through sweat, and provide sensations like touch, pain, and temperature. To maintain homeostasis, the body uses many control systems. These systems constantly monitor body conditions and make corrections when something changes. Most of these mechanisms work through Negative Feedback. In negative feedback, if a body variable increases or decreases from normal, the body triggers responses that bring it back toward the normal level. For example, if carbon dioxide levels in the blood increase, the respiratory center in the brain increases breathing rate to remove excess carbon dioxide. Similarly, special receptors called baroreceptors help regulate blood pressure. The efficiency of these control systems is measured by gain, which indicates how effectively the body corrects disturbances and maintains normal conditions.