Physiology · MU Pleven

Homeostasis

Explains homeostasis and how the body keeps its internal conditions stable, with notes on the roles of the liver, kidneys and other regulatory organs. It then distinguishes open from closed control systems, describes negative feedback loops with their gain formula, and covers positive feedback loops using a haemorrhage vicious-cycle example.

Inside: 6 sections · 2 labelled pictures · 1 formula · 15 flashcards · 4 min

Topic 1 of 17 in the MU Pleven syllabus for Physiology (Medicine, Year 2). The free AceMed note covers it in 6 sections, about 560 words (4 min of reading), with 15 flashcards.

In this note

  1. TOPIC 1. HOMEOSTASIS. FUNCTIONAL SYSTEMS OF THE BODY. CONTROL SYSTEMS OF THE BODY. NEGATIVE AND POSITIVE FEEDBACK LOOPS.
  2. HOMEOSTASIS
  3. FUNCTIONAL SYSTEMS OF THE BODY
  4. CONTROL SYSTEMS OF THE BODY
  5. NEGATIVE FEEDBACK LOOP
  6. POSITIVE FEEDBACK LOOP

HOMEOSTASIS

HOMEOSTASIS à derived from Greek “homeo” = constant, and “stasis” = stable à it means remaining stable or remaining the same.

The human body manages a multitude of highly complex interactions to maintain balance or return systems to functioning within a normal range.

  • These interactions within the body facilitate compensatory changes supportive of physical and psychological functioning.
  • This process is essential to the survival of the person and to our species.

FUNCTIONAL SYSTEMS OF THE BODY

Cells are the living units of the body:

  • Each organ is an aggregate of many cells held together by intercellular supporting structures.
  • The entire body contains about 75 to 100 trillion cells, each of which is adapted to perform special functions:
  • These individual cell functions are coordinated by multiple regulatory systems operating in cells, tissues, organs and organ systems.

Essentially all of the organs and tissues of the body perform functions that help maintain the constituents of the extracellular fluid relatively constant.

  • The liver, the kidneys, the brain (hypothalamus, the autonomic nervous system), and the endocrine system help maintain homeostasis.
  • LIVER à responsible for metabolizing toxic substances and maintaining carbohydrate metabolism.
  • KIDNEYS à responsible for regulating blood water levels, reabsorption of substances into the blood, maintenance of salt levels in the blood, control of blood pressure, regulation of blood pH, and excretion of urea and other wastes.

An inability to maintain homeostasis may lead to death or disease à HOMEOSTATIC IMBALANCE.

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