General Physiology PDF

General physiology D/Suzan Mustafa Hazzaa Professor of clinical physiology Physiology department Menoufia University Composition of the human body The human body is composed of various molecules, including: 1. Water (H2O), which constitutes about 60% of the total bod...

General physiology D/Suzan Mustafa Hazzaa Professor of clinical physiology Physiology department Menoufia University Composition of the human body The human body is composed of various molecules, including: 1. Water (H2O), which constitutes about 60% of the total body weight. 2. Proteins: About 18% of the body weight. 3. Lipids (fats): Around 15% of the body weight. 4. Minerals: About 5% of the body weight. 5. Nucleic Acids: A small but essential part, including DNA and RNA. 6. Carbohydrates: Less than 1% of the body weight, stored as glycogen in the liver and muscles. Organ Systems These tissues and cells are organized into complex tissues and organs: 1. Integumentary System: Skin, hair, nails. 2. Skeletal System: Bones, joints. 3. Muscular System: Skeletal muscles. 4. Nervous System: Brain, spinal cord, nerves. 5. Endocrine System: Glands that secrete hormones. 6. Cardiovascular System: Heart, blood vessels. 7. Lymphatic System: Lymph nodes, lymphatic vessels. 8. Respiratory System: Lungs, airways 9. Digestive System: Stomach, intestines, liver. 10. Urinary System: Kidneys, bladder. 11. Reproductive System: Ovaries/testes, associated organs. Total body water (TBW):  Total body water (TBW): TBW makes up approximately 55 to 60% of body weight in adult males. This percentage can change, depending on age, gender, and degree of obesity, It is about 50 to 55%, in adult females (due to a higher proportion of body fat). For a 70 Kg man, body water is around 42 L. Distribution of Body water Intracellular fluid: that located inside cells, approximately 40% of body weight. Extracellular fluid: that located outside cells, approximately 20% of body weight (interstitial fluid 15% and plasma (5%). Variations in body water Age: ✓ Infants: 75-80% of their body weight. ✓ Children: 65-70%. ✓ Adults: 60% body water, while adult females have about 55%. ✓ Elderly: 50-55% in old people. Sex: ✓ Males: (60%) because they generally have more muscle mass. ✓ Females: Usually have a lower percentage of body water (50-55%) due to higher body fat content and less muscle mass.  Body Composition: ✓ Muscle Mass: Individuals with more muscle mass have a higher body water. ✓ Body Fat: Individuals with higher body fat contents have lower body water. Health Status: ✓ Dehydration: Reduces body water content. ✓ Overhydration: Increases body water content.  Function of body water Water as a building material: Water, present in each cell of our body, acts first as a building material, so the water needs are higher during the growth period of the body. Water as a solvent: Water has unique properties; it is an excellent solvent for ionic compounds and for solutes such as glucose and amino acids. Water as a carrier: Water is essential for cellular homeostasis because it transports nutrients to cells and removes wastes from cells, allowing exchanges between cells, interstitial fluid and capillaries. Water and thermoregulation: Water has a large heat capacity, which contributes to limiting changes in body temperature in a warm or cold environment. Water as a lubricant and shock absorber: Water, in combination with viscous molecules, forms lubricating fluids for joints.  High extracellular High intracellular contents contents Na+, Cl -, bicarbonate K+, MG++, PH Proteins Difference between intracellular and extracellular ions Transport across the cell membrane Transport across the cell membrane is important for maintaining cellular homeostasis and enabling the exchange of substances between the cell and extracellular space. There are several mechanisms by which substances can be transported across the cell membrane, including passive transport and active transport. Transport occurs by one of the following ways: 1. Passive Transport. 2. Active Transport. 3. Bulk transport. 1-Passive Transport Is a type of cellular transport that allows movement of molecules across the cell membrane. Characters: a) According to the concentration gradient. b) Does not require ATP or other forms of cellular energy. c) Selective Permeability. d) Equilibrium.  Types of passive transport 1. Simple diffusion: 2. Facilitated diffusion: 3. Osmosis: Movement of small Movement of larger Movement of water across molecules directly through molecules across the a semipermeable the lipid bilayer according membrane via specific membrane according to to concentration gradient. transport proteins concentration gradient (Carrier Proteins). Water moving into cells in (e.g., oxygen and carbon (e.g., glucose, ions) dioxide) a hypotonic environment. Factors affecting diffusion: Fick’s laws describe the factors affecting the rate of diffusion. This can be written as follows: Rate of diffusion = (surface area x concentration gradient)/(length of diffusion pathway) 1. Concentration Gradient. The greater the concentration difference (∆C), the greater is the rate of diffusion. 2-Temperature: The greater the temperature (T), the greater the molecular motion and greater the diffusion. 3- Diffusion Distance: It is the thickness of the cell membrane. 4- Surface area: The larger the surface area the more space for diffuse of molecules. 5. molecular size: The smaller the molecules the faster the rate of diffusion. 6. Solubility: It is the ability of the diffusing substance to dissolve in the medium. So, lipid-soluble molecules diffuse more rapidly through the lipid bilayer. 2-Active Transport Active transport requires energy (ATP) to move substances against their concentration gradient. Types: a) Primary active transport. b) Secondary active transport. 1. Primary active transport: ✓ Mechanism: Direct use of ATP to transport molecules against concentration gradient. ✓ Example: (Na⁺/K⁺-ATPase pump) maintaining high K⁺ and low Na⁺ concentrations inside cells. Functions of Na/K ATPase pump in the body: Maintenance of Resting Membrane Potential: Regulation of Cell Volume: o Helps to regulate osmotic balance and, consequently, cell volume. Nerve Impulse Transmission: o The gradients established by the pump are used during the action potential of neurons, necessary for nerve signal transmission. Muscle Contraction: o Proper function of the pump ensures that muscle cells can respond to stimuli and contract effectively.  2. Secondary active transport: ✓ Mechanism: Uses the energy from the primary active transport to move another molecule. ✓ Types: Symport: Both molecules move in the same direction (e.g., glucose-Na⁺ symporter). Antiport: Molecules move in opposite directions (e.g., Na⁺/Ca²⁺ exchanger). ✓ Example: Glucose uptake in the intestines via the sodium-glucose co-transporter. 3- Bulk Transport Bulk transport involves the movement of large molecules or particles via vesicles and requires energy. Types: a) Endocytosis. b) Exocytosis.  a) Endocytosis: Mechanism: The cell membrane engulfs material to form a vesicle that brings substances into the cell. Types: Phagocytosis. Pinocytosis. Receptor-Mediated Endocytosis: Specific uptake of molecules based on receptor binding (e.g., uptake of cholesterol via LDL receptors).  a) Exocytosis: Mechanism: Vesicles fuse with the cell membrane to release their contents outside the cell. Types: Secretion of neurotransmitters from neurons.