Lecture 1: Introduction to Physiology & Membrane Transport PDF

1 LECTURE 1 : a INTRODUCTION TO PHYSIOLOGY AND MEMBRANE TRANSPORT Course: Physiology for Physiotherapy Monday 14 October 2024 2 Physiology It’s a branch of science dealing with normal body functions and the integration of functions between dif...

1 LECTURE 1 : a INTRODUCTION TO PHYSIOLOGY AND MEMBRANE TRANSPORT Course: Physiology for Physiotherapy Monday 14 October 2024 2 Physiology It’s a branch of science dealing with normal body functions and the integration of functions between different systems and how these functions occur. Homeostasis: It means keeping the internal environment of the body constant, i.e. maintenance of physical and chemical composition of the extracellular fluid in constant state. Monday 14 October 2024 3 Feedback Loops Sensor: Detects deviation from set point. Integrating center: Determines the response. Effector: Produces the response. Monday 14 October 2024 4 Negative Feedback Monday 14 October 2024 5 Positive Feedback - Action of effectors amplifies the change. - Is in same direction as change. Examples: 1- Estrogen and luteinizing hormone in the first half of the menstrual cycle. 2- Oxytocin (parturition). 3- Voltage gated Na+ channels (depolarization) Monday 14 October 2024 6 Human Body Cells Tissue Organ System Human Body Monday 14 October 2024 7 BODY WATER - Water constitutes about 60% of total body weight (in adult male weighting 70Kg, about 40 L water) - The amount of water decline (decrease) with age: in a new born 80% and in old age 50%. - In fatty persons the body water is less than normal as adipose tissue contain less water. - Also female contain less water content than male. Monday 14 October 2024 8 Total body water (Inside cells) (Outside cells) Intracellular Extracellular (2/3body water) (1/3 body water) Interstitial fluid Plasma Monday 14 October 2024 9 Intracellular fluid (water) inside cells extracellular fluid Monday 14 October 2024 10 THE CELL The cell is the structural unit of the body, It is formed of a protoplasmic mass (Cytoplasm & Nucleus) surrounded by a cell membrane Monday 14 October 2024 11 The Cell Membrane Size should 24  Many Functions of Membrane Proteins Outside Plasma membrane Inside Transporter Enzyme Cell surface activity receptor Cell surface Cell adhesion Attachment to the identity marker cytoskeleton  TYPES OF CELL MEMBRANE CARRIER PROTEINS 1) Uniport carrier protein: That transports a single particle in one direction. e:g facilitated diffusion of glucose. 2) Symport carrier protein: That transports 2 particles in same direction. e:g Co-transport of glucose with Na+. 3) Antiport carrier protein: That transports one substance in one direction and another substance in the opposite direction. e:g Na+ - K+ ATPase. MOVEMENT ACROSS THE CELL MEMBRANE RANSPORT ACROSS CELL MEMBRANE I-Passive transport: 1-Diffusion: a)Simple diffusion. b) Facilitated diffusion. 2-Osmsis. 3-Filtration. II-Active transport: 1-Primary Active transport. 2-Secondary Active transport. III-Endocytosis & Exocytosis.  I-Passive transport 1-Diffusion (a)Simple diffusion: It is the continuous movement of molecules in liquid or gas from region of high concentration to region of low concentration. CHARACTERESTICS 1) No energy is needed (passive transport). 2) Depends on presence of concentration gradient. 3) No need for carrier proteins. Simple Diffusion  Diffusion   movement from high low concentration FACTORS AFFECTING SIMMPLE DIFFUSION 1)Concentration gradient of the substance. 2)Molecular weight of the diffusible substance. 3)Total surface area of the membrane. 4)Thickness of the membrane. 5)Size of the pores of the membrane. 6)Water and lipid solubility of the diffusible substance. 7)Temperature. 8)Permeability of the membrane to the substance. Diffusion is directly proportional to: 1)Temperature of the solvent. 2)Surfaces area of the membrane. 3)Size of pores of the membrane. Diffusion is inversely proportional to: 1)Thickness of the cell membrane. 2)Molecular weight of the substance.  (b) Facilitated diffusion: It is the move of substance passively from region of high concentration to region of low concentration, and it requires a type of proteins in the cell membrane called carrier protein. e:g glucose and amino acids. Facilitated Diffusion Diffusion with help of carrier protein. The carrier moves specific molecules across cell membrane facilitated = with help No energy needed high low Process of Facilitated Transport Protein binds with molecule. Shape of protein changes. Molecule moves across membrane.  CHARACTERS OF FACILITATED DIFFUSION 1) Passive(no need for energy). 2) Needs carrier. 3) Substance moves down its concentration gradient. 4) Specificity of the carrier protein(each carrier is specific for certain substance).  2- Osmosis It is the diffusion of solvent molecule (water) from a region of low concentration of solute to region of high concentration of solute through a semi permeable membrane. Tonicity Means osmolality of solution relative to plasma. Isotonic – the same osmolality as plasma e.g. NaCl 0.9%. Hypertonic - has osmolality more than plasma. Hypotonic – has osmolality less than plasma. water hypotonic hypertonic net movement of water Monday 14 October 2024 27 3-Filtration * It means forcing fluid through a membrane due to a difference in hydrostatic pressure on 2 sides of the membrane. *The amount of the fluid filtered is directly proportional to the pressure gradient , surface area of the membrane and the permeability of the membrane. - Importance:- 1) Formation of interstitial fluid. 2) Formation of Urine. Monday 14 October 2024 28 II-Active transport 1-Primary Active transport CHARACTERS (1) It occurs against concentration gradient. (from low to high concentration). (2) Needs energy (supplied directly from ATP) (so its active) (3) Needs carrier. Example: Na+- K+ pump (Sodium Potassium Pump) : - The carrier contain receptor sites for sodium & potassium and it pumps sodium to outside the cell while potassium to inside the cell. - It contain Na+ - K+ ATPase enzyme that hydrolyses ATP to produce energy which is used for this process. (For each 2K+ pumped inside 3 Na+ pumped outside). Monday 14 October 2024 29 2- Secondary Active transport CHARACTERS 1- It occurs against concentration gradient (from low to high concentration). 2- It needs carrier. 3- The energy is supplied indirectly from the concentration gradient of the sodium induced by the primary active transport. Examples: a) Glucose- Na+ Co transport b) Amino acid- Na+ Co transport. c) Ca +2 - Na+ Counter transport.  Secondary Active transport Energy is supplied indirectly from conc. gradient of Na induced by Na/K pump Ca+2 Antiport Symport countertran cotrans Monday 14 October 2024 31 In case of glucose and amino acid the molecules are transport with sodium in the same direction so it's (Co transport). While in case of calcium they are transport in the opposite direction so it's (Counter transport). Monday 14 October 2024 32 III- Endocytosis & Exocytosis. (a) Endocytosis CHARACTERS: 1) It is an active transport (Needs energy). 2)The carrier protein is a part of the cell membrane. 3) Includes 2 types:- (a)Pinocytosis:- Cell drinking. (b)Phagocytosis:- Cell eating. Monday 14 October 2024 33 Process of Endocytosis Plasma membrane surrounds material. Edges of membrane meet. Membranes fuse to form vesicle. Monday 14 October 2024 34 (b)Exocytosis Reverse of endocytosis. Cell discharges material.