Lecture 7 & 8 Homeostasis PDF

Lecture 7 & 8 Homeostasis Dr. Safa Almaghrabi MBBS, MBiomedSc, PhD Associate Professor in Clinical Physiology Department Email: [email protected] 1  Lecture Objectives By the end of t...

Lecture 7 & 8 Homeostasis Dr. Safa Almaghrabi MBBS, MBiomedSc, PhD Associate Professor in Clinical Physiology Department Email: [email protected] 1  Lecture Objectives By the end of this lecture, the student should be able to: 1. Define the internal and external environment of an organism 2. Define homeostasis and discuss its importance 3. Describe the components of a homeostatic control system 4. Discuss the role of the nervous system and endocrine system in coordinating and mediating homeostatic responses 5. Describe how different body systems contribute to homeostasis 6. Illustrate the principles of the negative feedback mechanism in miniating homeostasis with examples. 7. Illustrate the principles of a positive feedback mechanism in miniating homeostasis with examples. 8. Predict the impact of disruptive homeostasis 2 3  Internal Environment Internal environment = fluid surrounding cells = extracellular fluid (ECF). The chemical composition and physical state of the internal environment are kept relatively constant by homeostatic mechanisms. Cells are capable of living and performing their special functions as long as the proper concentrations of oxygen, glucose, different ions, amino acids, fatty substances, and other constituents are available in this internal environment. 4  Homeostasis Homeostasis is the ability of the body to maintain a relatively stable internal environment despite changes in the surroundings. “homeo”= the same “stasis”= to standing still 6  Homeostasis Importance of homeostasis: An organism functions more efficiently if conditions are maintained within narrow limits close to optimum conditions. The chemical composition & physical state of the internal environment can be allowed to deviate only within narrow limits. 7  Homeostatically Regulated Factors Many factors of the internal environment must be homeostatically maintained. They include the following: 1. Concentration of: · c attacks a nutrient molecules O2 and CO2 > thats why - hal we give plastic divin bay waste products water, salt and other electrolytes 2. pH 3. Temperature 4. Plasma volume and blood pressure Salt >> water >> plasma volume >> blood pressure 8 ↳ u In 9  Homeostatic Control Systems Network of body components that operate to maintain a given factor in the internal environment relatively constant around an optimal level. Classes of control system its self work alone 1. Intrinsic (local) - the system 2. Extrinsic (systemic) - Nervous system (fast) Ycontroltems ↳ week to - Endocrine system (slow) at because we for 70 - wait Control systems operate by two mechanisms: hormones Her Negative feedback (main) leave u , und Positive feedback 9 into t 10  What is Feedback? Feedback refers to responses made after a change has been detected. 11 Components of the Feedback Loop 12  Negative Feedback Refers to the mechanism by which a system responds to a fluctuation in the opposite direction Body temperature Corrective mechanism RISES DECREASES body temperature 13  14 Sherwood L, Human Physiology: From Cells to Systems. 9th edition. 2016 Examples of Negative Feedback Mechanisms 15 Regulating Red Blood Cells Production 16 Regulating Blood Sugar level 17 Regulating Blood Pressure 18  Positive Feedback Mechanisms A disturbance leads to events which increase the disturbance even further. Continues increasing or decreasing a change. MOST positive feedback are dangerous and lead to death. 19 Example of a Positive Feedback Mechanism 20 Regulating Uterine Contraction 21 Regulating Blood Clot Formation 22 Example of a Positive feedback Vicious cycles lead to death 23  Disturbance of Homeostasis Pathophysiological states (disease) develop when one or more of the body systems fail to function properly so that an optimal internal environment can no longer be maintained. Serious homeostatic disruption leads to death. 24