Homeostasis PPT PDF

INTRODUCTION TO HOMEOSTASIS Dr Nisreen Daffa Alla M.B.B.S, Ph. D, MSc Health Profession Education Important variables within the body:  Fluid balance  Body temperature  Oxygen& carbon dioxide levels  Blood pressure  pH  Plasma level of creatinine, urea, sodium, potassium, glucose...

INTRODUCTION TO HOMEOSTASIS Dr Nisreen Daffa Alla M.B.B.S, Ph. D, MSc Health Profession Education Important variables within the body:  Fluid balance  Body temperature  Oxygen& carbon dioxide levels  Blood pressure  pH  Plasma level of creatinine, urea, sodium, potassium, glucose, amino acids, etc….. These variables must stay within certain ranges.  Changes in the external environment can cause these variables to change. Homeostasis: definition is: The process by which a stable or constant internal environment is maintained despite changes in the external environment. What is the internal environment of the body? The Internal body enviroment The internal environment of an organism is the extracellular fluid the fluid environment surrounds cells, exchanges nutrients and wastes, and acts as a buffer. The cell is the simplest unit of life. The cell needs a constant internal environment. Cells obtain nutrients from, and remove wastes to, the internal environment. Homeostasis is necessary for healthy cells. Major systems control homeostasis  All different body systems operate in harmony to provide homeostasis Endocrine and nervous systems are the major control systems Nervous system – Controls and coordinates bodily activities that require rapid responses Endocrine system – Regulate activities that require duration rather than speed. Components of a homeostatic control system Receptor = The structure that detects changes in a variable, the stimulus e.g., a change in temperature. Afferent pathway: send the data to the control center C. Control Center= receives data, interprets information, sends messages out.  brain  Endocrine glands D. Communication System/efferent= delivers messages to effector organs, tissues PNS (e.g. motor neurons) Hormone E. Effectors = respond to change. It can be muscles or glands (release hormones)  3 Input: Control center 4 Output: Information Information sent sent along along efferent afferent pathway to pathway to Receptor (sensor) Effector 2 Change detected by receptor Homeostatic Control Mechanisms 5 Response of effector feeds back to influence 1 Stimulus: magnitude of Produces I mb stimulus and al a change nce returns in variable variable to homeostasis Variable (in homeostasis) I mb al a nce 8 The hypothalamus  Part of the brain  Often serves as the co-ordinating centre: Receives messages from receptors  Initiates a hormonal/nervous response Homeostatic control mechanisms The control centers function to maintain homeostasis through Feedback & feedforward mechanisms. Types of feedback mechanism are: 1. Negative feedback 2. Positive feedback  Homeostatic Control Systems Feedback - refers to responses made after change has been detected – Types of feedback systems Negative Positive 11 Negative feedback Negative feedback: Response triggered by changed conditions serves to reverse the change E.g., Body temperature increases  Skin blood vessels dilate  Body temperature decreases Resulting action is in the opposite direction of stimulus If stimulus increases, homeostatic control system activated to cause a decrease in the stimulus If stimulus decreases, homeostatic control  Body temperature increases Normal Hypothalamu body s sends a temperat message to ure blood vessels Body Skin blood temperature vessels decreases dilate  Glucose Homeostasis Chart Low Blood Sugar Condition High Blood Sugar Do not meet energy Toxic requirements of cell Receptor Glucose transporter Glucose transporter Control -cell of the pancreas -cell of the pancreas Center Effector Insulin Glucagon Glucose uptake by Liver breaks down muscle/fat tissue glycogen to create Result Lowers blood-glucose glucose Raises blood-glucose Positive feedback  Positive feedback: The response triggered by changing conditions serves to move the variable even further away from its steady state  E.g., uterine contractions are stimulated by oxytocin  baby moves towards cervix  more oxytocin is released Homeostatic Systems Regulated by Positive Feedback Positive feedback during breastfeeding Sensory detectors detect baby suckling Message is transmitted to the hypothalamus Hypothalamus signals posterior pituitary to release the hormone oxytocin Oxytocin stimulates the mammary Feedforward control Based on forecast result or anticipated change. The response of the control system is taken well in advance of actual result Example: rise of heartbeat in advance of actual physical exertion by the central autonomic network. Feed-forward control can be likened to learned anticipatory responses to known cues (predictive coding). Significance of homeostasis Homeostasis maintains a relatively stable internal environment, allowing the body to adapt to external changes while preserving essential functions. Survival: Every living organism relies on homeostatic processes for survival. Imbalance and Disease: When homeostasis fails, internal imbalances can lead to sickness or even death. For example, diabetes occurs when blo od sugar homeostasis is disrupted. A disruption of homeostasis is harmful.  Homeostasis can be disrupted for several reasons. 1. Sensors fail (don’t detect changes) 2. Effectors do not receive messages (nerve, endocrine issues) 3. Injury (overwhelm homeostatic controls) 4. Illness (viruses or bacteria) *Disruption of homeostasis can begin in one organ and cause a chain reaction in the others therefore causing a major body disturbance. 23