3. Homeostatis.ppt
- 2. CONTENTS • Objectives • Introduction • Definitions
- 3. Objectives •Define homeostasis. •Describe the components of a feedback system. •Contrast the operation of negative and positive feedback system
- 4. Homeostasis • Homeostasis ( homeo- sameness; -stasis standing still) is the tendency of organisms to auto-regulate and maintain the internal environment in stable state .
- 5. Feedback Systems • The body can regulate its internal environment through many feedback systems. A feedback system or feedback loop is a cycle of events in which the status of a body condition is • Monitored • Evaluated • changed, • Re-monitored, • Re-evaluated, and so on. Each monitored variable, such as body temperature, blood pressure, or blood glucose level, is termed a controlled condition.
- 7. Stimulus •Any disruption that changes a controlled condition is called a stimulus. •A feedback system includes three basic components— •a receptor •a control centre • an effector
- 8. Receptor •A receptor is a body structure that monitors changes in a controlled condition and sends input to a control centre. •Typically, the input is in the form of nerve impulses or chemical signals. •For example, certain nerve endings in the skin sense temperature and can detect changes, such as a dramatic drop in temperature. .
- 9. Control Centre Brain, sets the range of values within which a controlled condition should be maintained, evaluates the input it receives from receptors, and •Generates output commands when they are needed. • In our skin temperature example, the brain acts as the control centre, receiving nerve impulses •From the skin receptors and generating nerve impulses as output.
- 10. Effector • Body structure that receives output from the control centre and produces a response or effect that changes the controlled condition. • When your body temperature drops sharply, your brain (control centre) sends nerve impulses (output) to your skeletal muscles (effectors). • The result is shivering, which generates heat and raises your body temperature
- 11. NEGATIVE FEEDBACK SYSTEMS • A negative feedback system reverses • a change in a controlled condition. Consider the regulation of blood pressure. Blood pressure (BP) is the force exerted by blood as it presses against the walls of blood vessels. When the heart beats faster or harder, BP increases. If some internal or external stimulus causes blood pressure (controlled condition) to rise, the following sequence of events occurs (Figure 1.3). • Baroreceptors (the receptors), pressure-sensitive nerve cells located in the walls of certain blood vessels, detect the higher • pressure. The baroreceptors send nerve impulses (input) to the brain (control center), which interprets the impulses and responds • by sending nerve impulses (output) to the heart and blood vessels (the effectors). Heart rate decreases and blood vessels dilate (widen), which cause BP to decrease (response).
- 12. • This sequence of events quickly returns the controlled condition— • blood pressure—to normal, and homeostasis is restored. the activity of the effector causes BP to drop, a result that negates the original stimulus (an increase in BP). This is why it is called a negative feedback system.
- 14. POSITIVE FEEDBACK SYSTEMS •A positive feedback system tends to strengthen or reinforce a change in one of the body’s controlled conditions. •The control centre still provides commands to an effector, but this time the effector produces a physiological response that adds to or reinforces the initial change in the controlled condition. •The action of a positive feedback system continues until it is interrupted by some mechanism.
- 15. • feedback system. The first contractions of labor (stimulus) push part of the foetus into the cervix, the lowest part of the uterus, which opens into the vagina. • Stretch-sensitive nerve cells (receptors) monitor the amount of stretching of the cervix (controlled condition). As stretching increases, they send more nerve impulses (input) to the brain (control center), which in turn releases the hormone oxytocin (output) into the blood.
- 16. • Oxytocin causes muscles in the wall of the uterus (effector) to contract even more forcefully. The contractions push the foetus farther down the uterus, which stretches the cervix even more. • The cycle of stretching, hormone release, and ever-stronger contractions is interrupted only by the birth of the baby. Then, stretching of the cervix ceases and oxytocin is no longer released
- 18. Homeostatic Imbalances • If the homeostatic imbalance is moderate, a disorder or disease may occur; if it is severe, death may result.
- 19. • A disorder is any abnormality of structure or function. • Disease is a more specific term for an illness • A local disease affects one part or a limited region of the body; • a systemic disease affects either the entire body or several parts of it. • Symptoms subjective changes in body functions that are not apparent to an observer. • Examples include headache, nausea, and anxiety. Signs of disease can be either anatomical, such as swelling or a rash, or physiological, such as fever, high blood pressure, or paralysis. • Epidemiology :-The science that deals with why, when, and where diseases occur and how they are transmitted among individuals in a community • Pharmacology is the science that deals with uses of drugs in the treatment of disease.
- 20. What to think? • Describe the locations of intracellular fluid, extracellular fluid, interstitial fluid, and blood plasma. • Why is interstitial fluid called the internal environment of the body? • What types of disturbances can act as stimuli that initiate a feedback system? • How are negative and positive feedback systems similar? How are they different? • What is the difference between symptoms and signs of a disease? Give examples of each.
- 21. REFERENCES • Essentials of Medical Physiology by K. Sembulingam and P. Sembulingam. Jaypee Brothers Medical Publishers, New Delhi. • Anatomy and Physiology in Health and Illness by Kathleen J.W. Wilson, Churchill Livingstone, New York. • Physiological basis of Medical Practice-Best and Tailor. Williams and Wilkins Co, Riverview, MI USA. • Text book of Medical Physiology- Arthur C, Guyton and John.E. Hall. Miamisburg, OH, U.S.A. • Principles of Anatomy and Physiology by Tortora Grabowski. Palmetto, GA, U.S.A. • Human Physiology (vol 1 and 2) by Dr. C.C. Chatterrje, Academic Publishers Kolkata.
- 22. THANKS
Editor's Notes
- #4: Firstly, we are going to start by looking at the definition of validation and the different types that are used. Secondly, we will discuss documents associated with validation, and review the key stages of the validation process. Thirdly, we shall look at a model approach for process validation in the context of the WHO documentation. Finally, we are going to look at where validation has got to in your country and talk about the barriers that need to be overcome. This module will deal with the very fundamentals of validation but it will only provide an overview. It will not be an in-depth review of the subject. The subject is very important and requires a lot of careful thought. It will be a major topic of discussion with companies that you inspect and also within the inspectorate. It is important to remember that validation does not improve bad processes.