MBBS 2024 Homeostasis 2nd Lecture PDF

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1 d dy! an bo e hum of th tudy ting s scina to t he fa ome Welc Physiology The Cell 2nd Lecture 2024  Major Topics ❖ Homeostasis ❖ Membrane Structure and Function ❖ Lipid Bilayer ❖ Membrane proteins 2  Learning Objectives After this lecture, you should be able to: ❖ Define homeostasis ❖ Identify the components of Negative Feedback Loops ❖ Explain the role of antagonistic effectors in maintaining homeostasis ❖ Explain the nature of Positive Feedback Loops ❖ Describe the MEMBRANE STRUCTURE AND FUNCTION and also the physiological roles of Membrane Lipids 3 4 Homeostasis Homeostasis {homeo-, similar + stasis, condition} ▪ Homeostasis Maintains Internal Stability Homeostasis and regulation of the internal environment are key principles of physiology. BODY FLUID COMPARTMENTS 5  The adult human body is made up of 60% water and is divided into extracellular and intracellular fluid compartments. Hypernatremia, hyponatremia, and edema are the clinical conditions arising from disturbances in the maintenance of osmolarity of the body fluid compartments. 6  Homeostasis and Feedback Control The concept of a relatively stable internal environment is attributed to the French physician Claude Bernard in the mid-1800s. In 1929, an American physiologist named Walter B. Cannon proposed a list of variables that are under homeostatic control. 7  What Is the Body’s Internal Environment? If the body fails to maintain homeostasis, then normal function is disrupted and a disease state, or pathological condition may result. Diseases fall into two general toxic chemicals groups according to their origin cancer physical trauma tumors foreign invaders; autoimmune diseases such as viruses and bacteria death of cells failure of cell processes inherited disorders If compensation fails, illness If the compensation is successful, or disease may result. homeostasis is restored. diabetes mellitus 8 Most cells in our bodies are not very tolerant of changes in their surroundings. Therefore, there should be precise physiological processes have evolved to keep its composition relatively stable But what exactly is the internal environment of the body? 9 The body’s Internal and External Environments ▪ Homeostasis Maintains Internal environment Stable ▪ Internal environment = Extracellular Fluid Homeostasis is not a rigid, fixed state or absolute setting, but rather a dynamic. 10  Mass Balance The total amount of substance x in the body = (intake + production) – (excretion – metabolism) 11  Homeostasis typically involves negative feedback loops that counteract changes of various properties from their target values, known as set points. all control systems have three components: (1) an input signal; (2) a controller, or integrating center that integrates incoming information and initiates an appropriate response; and (3) an output signal that creates a response. 12 Homeostasis (A millimeter of mercury) 13 FACTORS HOMEOSTATICALLY REGULATED 1. Concentration of nutrient molecules 2. Concentration of oxygen and carbon dioxide 3. Concentration of waste products 4. Changes in the pH 5. Concentration of water, salt, and other electrolytes 6. Volume and pressure 7. Temperature 14  Feedback Mechanisms Negative Feedback Positive Feedback Homeostatic responses in temperature regulation 16 Negative feedback control of blood pressure 17 Negative feedback control of blood Glucose N.F N.F 18 Some biological systems, however, use Positive Feedback Loops In contrast to negative feedback loops, positive feedback loops amplify their initiating stimuli; in other words, they move the system away from its starting state 19  Examples for the positive feedback loops: Childbirth – stretching of uterine walls cause contractions that further stretch the walls (this continues until birthing occurs) Lactation – the child feeding stimulates milk production which causes further feeding (continues until baby stops feeding) Action Potential Firing – during depolarization phase, more opening the voltage–gating Na+ channel , more depolarization of membrane Blood Clotting – platelets receive a signal, activate and form blood clot, activated platelets send signal to activate more platelets Menstrual Cycle – Increased LH secretion stimulates estrogen production from the ovary which through positive feedback leads to the midcycle LH surge that causes ovulation.  Positive Feedback Loops Childbirth – stretching of uterine walls cause increase in Oxytocin release, Oxytocin stimulates contractions that further stretch the walls, (this continues until birthing occurs)  Menstrual Cycle – Increased LH secretion stimulates estrogen production from the ovary which through positive feedback leads to the midcycle LH surge that causes ovulation. Thanks for listening Any Q?