Lecture 1: Human Physiology - Body Fluid Compartments PDF

Lecture 1 physiology INTRODUCTION TO HUMAN PHYSIOLGY BODY FLUID COMPARTMENTS Definition of Human Physiology: Physiology is a Latin word divided into 2 parts:  Physio = means Function.  Logy = means Science. So, Human Physiology is the science that deals with the fun...

Lecture 1 physiology INTRODUCTION TO HUMAN PHYSIOLGY BODY FLUID COMPARTMENTS Definition of Human Physiology: Physiology is a Latin word divided into 2 parts:  Physio = means Function.  Logy = means Science. So, Human Physiology is the science that deals with the functions of the human body under different environmental conditions (internal or external) in order to maintain life. Human Body Organization:  The cell is the smallest basic structural unit of the human body.  A tissue is formed of a group of cells arranged side-by side & having the same shape, structure and function.  An organ consists of more than one tissue and performs a specific function; e.g. the teeth masticates and the heart beats to pump the blood.  A system consists of more than one organ performing complementary functions, all of which determine the characteristic role of that system in life.  Thus, our bodies consist of a group of systems; each of them plays a specific role in our body and the sum of these roles altogether are essential to keep our lives. Examples of Different Body Systems: * The Cardiovascular System * The Endocrine System. * The Respiratory System. * The Nervous System. * The Urinary System. * The Reproductive System. * The Digestive System * The Musculoskeletal system. CHEMICALLY, Human Body is composed of:  Water (60%).  Solids (40%); either; a. Organic (protein 18% - fat 15%). b. Inorganic (minerals 7%). BODY FLUIDS:  The total body water is normally about 60% of the body weight in young adult males.  Therefore, in a young adult male weighing 70 Kg, the total body water is normally about 42 litres, and it is distributed as follows: (1) Intracellular fluid (ICF): it represents about 2/3 of the total body water i.e. about 40% of the body weight (~28 L). (2) Extracellular fluid (ECF): it represents about 1/3 of the total body water i.e. about 20% of the body weight (~ 14 L). It includes the following subdivisions: a) Intravascular fluid (i.e. blood plasma): This is normally about 1/4 of the ECF volume. b) Extravascular fluid: This is normally about 3/4 of the ECF volume. It includes the interstitial fluid + transcellular fluids. N.B.  Interstitial or intercellular or tissue fluid): the fluid in spaces in between tissue cells.  Transcellular fluids: the fluid present in closed spaces surrounded by epithelium. e.g. cerebrospinal fluid, intraocular fluids, and the fluids in the pleura, joints, peritoneum, etc. Calculate the total body water of a 40 years adult male, 70 Kg: Total Body Water = 60/100 * 70 = 42 litres How many litres lie intracellularly? 42 X ⅔ = 28L OR 70 X 40/100 = 28L. How many litres lie extracellularly? 42 X ⅓ = 14L OR 70 X 20/100 = 14L. Composition of ECF vs. ICF: Item ECF ICF Mainly Na+ (142 mEq/L) Mainly K+ (140 mEq/L) & K (4 mEq/L) Mg2+ Main cation + small amounts of Ca2+ and small amounts of Na Mg2+ very little Ca2+ Cl- HPO4 & protein. -, Main anion small amounts of: HCO-3, Small amounts of Cl HCO3 proteins, and HPO4 and SO4 pH About 7.4 About 7 due to low HCO-3 Osmolarity The same The same Functions of Body Water: 1. It is the medium for chemical and enzymatic reactions. 2. It is the medium for the physical processes e.g. diffusion and filtration. 3. It is an ionizing medium (in regulating pH and body fluid osmolarity). 4. Regulation of body temperature. 5. It is a lubricant in the joints and potential spaces (e.g. the pleura). 6. It is a refractive medium in the eye. 7. The cerebrospinal fluid is a mechanical buffer that protects the brain. 8. It is the medium for gas exchange (O2 & CO2) in lungs and tissues. ***************************************************  Human Cell; Cell Membrane Structure & Function The cell is the Building (Structural) Unit of the human body. THE CELL MEMBRANE: Functions: 1. It forms the outer boundary surrounding the cell to protect it from the external environment. 2. Selective permeability; as it permits the passage of certain substances and prevents others. 3. Very thin; 75 angstroms. Chemical Structure: It is formed of lipid (phospholipid(flexibility and cholesterol tufness), Proteins and carbohydrates a. Phospholipids: - Each phospholipid molecule in the cell membrane is formed of: 1. Water soluble (hydrophilic) phosphate part (head). 2. Fat soluble (hydrophobic) lipid part (tail) containing cholesterol. - The plasma membrane is formed of two layers (bilayer) of phospholipid molecules with their hydrophilic phosphate heads directed outwards and inwards and their hydrophobic lipid tails directed to the interior of the membrane. b. Proteins: Proteins determine the cell membrane’s specific functions more active membrane= more ptn - Cell membrane proteins are formed of peptide chains of amino acids. - Chemically, they are either; 1. Pure proteins. 2. Conjugated proteins with carbohydrates (glycoproteins) or with lipids (lipoproteins). - According to their site; Proteins are either; 1. Peripheral proteins on the outer or inner surfaces. ex: cell surface identity marker (antigens especialy glycoptn carbohydrate), receptors (out side) or enzyme from (inside) 2. Through & through proteins (i.e. transmembrane or integral proteins). Channel , carrier and pump  Chemical Structure of Cell Membrane. Functions of Cell Membrane Proteins: 1. Surface proteins act as receptors or surface recognition sites (self-antigens ) Carbohydrate part→ very important for immune system to differentiate between what is self and non-self (foreign) → thus preventing the body from attacking itself (i.e. autoimmune diseases). 2. Act as active Pumps e.g. Na+-K+ pump. 3. Act as Receptors for;  Hormones.  Chemical transmitters. 4. Act as Enzymes e.g. adenylate cyclase enzyme → which catalyses the formation of cyclic AMP (cyclic AMP) from ATP. 5. Act as Carriers; helping transport of substances through the cell membrane. Types of Carriers: a) Uniport: transport one substance in one direction. b) Symport: cotransport more than one substance at a time in only one direction. c) Antiport: transport one substance in one direction in exchange for another in opposite direction e.g. Na+-K+ pump carrier → it transports 3 Na+ out of the cell in exchange with 2 K+ into the cell.  Types of cell membrane carrier proteins. 6. Act as Channels: through which water soluble substances can pass through the cell membrane. Types of Cell Membrane Channels: 1. Non gated channels: they are channels that are open all the time allowing passage of ions all the time. Sometimes they are called “leak channels”. 2. Gated channels: these channels are classified into: a. Voltage gated channels: they open or close in response to changes in membrane potential. b. Ligand gated channels: they open or close in response to binding to a chemical substance called (ligand), which may be either:  External ligands; binds to the outer surface of the cell membrane as neurotransmitters and hormones.  Internal ligands; binds to the inner surface of the cell membrane as Ca+2 and cyclic AMP. c. Mechanical gated channels: they open or close in response to mechanical stretch or pressure. Types of cell membrane channels