(LEC)Introduction to Physiology.pdf

 OBJECTIVES 1. Define important terms needed in the physiologic principles and anatomic structures. 2. Describe the over-all organization of the body. 3. Describe the organization, function, and characteristics of the cell. 4. Discuss cell membrane with emphasis on its control sy...

 OBJECTIVES 1. Define important terms needed in the physiologic principles and anatomic structures. 2. Describe the over-all organization of the body. 3. Describe the organization, function, and characteristics of the cell. 4. Discuss cell membrane with emphasis on its control systems. 5. Discuss and outline the initiation of action potential (AP), Resting Membrane Potential (RMP) and impulse transmission.  PHYSIOLOGY Is the study of function in living matter This field of Physiology can be divided into: 1. Viral physiology 2. Bacterial physiology 3. Cellular physiology 4. Plant physiology 5. Human physiology Human Physiology - we explain the specific characteristics and mechanisms of the human body that make it a living being  THE CELLS The basic unit of the body, and each organ is an aggregate of many different cells held together by intercellular supporting structures. Basic characteristics of cells: 1. In all cells, oxygen combines with carbohydrates, fat and protein to release the energy needed for cell function. 2. All the cells have the ability to reproduce and whenever cell are destroyed, one or another of the remaining cells divide again and again until the appropriate number is replenished. 3. The general mechanisms for changing nutrients into energy are basically the same in all cells. 4. All the cells deliver the end-products of their chemical reactions into the surrounding fluids. HOMEOSTATIC MECHANISMS OF THE MAJOR FUNCTIONAL SYSTEM HOMEOSTASIS means maintenance of static, or constant condition in the environment. All organs and tissues of the body perform functions that help to maintain these constant conditions. The Extracellular Fluid-The Internal Environment 60% of human body is fluid. This is made up of: Intracellular Fluid - this is the fluid found inside the cell which constitute most of the 40% of the total body fluid. Extracellular Fluid - this is found in the spaces outside the cells, and is in constant motion throughout the body. 1. The Extracellular Fluid Transport System The TransportS Nutrients ( Circulatory System) Transport of the extracellular fluid through all parts of the body entails the movement of the blood around the circulatory system and movement of fluid between the blood capillaries and the cells. 2. Origin of Nutrients in the Extracellular Fluid A. The Respiratory System - transports nutrients to tissues (O2) B. The Gastrointestinal Tract - absorption of nutrients into the extracellular fluid. C. The Liver - detoxification and storage of substances. D. Musculosketekal System - locomotion 3. Removal of Metabolic End-Products A. Removal of Carbon Dioxide by the Lungs blood picks up oxygen in the lungs, carbon dioxide is released from the blood into the alveoli, and the respiratory movement of air into and out of the alveoli carries the carbon dioxide to the atmosphere. B. The Kidneys removes different end products of metabolism and excess of ions and water that might have accumulated in the extracellular fluid. 4. Regulation of Body Functions A. The Nervous System - muscular and secretory activities B. The Hormones System - for metabolic function 5. Reproduction - maintain static conditions by generating new beings to take the place of ones that are dying. 6. Extraction of Energy from Nutrients (Mitochondria) The principal substances from which cell extracts energy are Oxygen and one or more of the foodstuffs - Carbohydrates, Fats and Protein. 7. Locomotion or Movements by the cells A. Ameboid locomotion - means the movements of an entire cell in relation to its surroundings, such as movement of WBC. B. Ciliary movements - the whiplike movement of cilia on the surface of the cells. Occurs in: 1. Respiratory airways 2. Uterine tubes THE CELL & ITS FUNCTION Organization of the Cell A typical cell has two major parts namely: A. Nucleus - separated from the cytoplasm by the nuclear membrane B. Cytoplasm - separated from the surrounding fluids by the cell membrane CHEMICAL COMPONENTS 1. Water - the principal medium Potassium of cell which is about 70 to Magnesium 80%. It provides transport of Phosphates substances from one part of Sulfate the cell to another. Bicarbonate 2. Electrolytes - provides Chloride (small quantities) inorganic chemicals for cellular reactions and for the Calcium (small quantities) operation of same cellular control mechanisms. CHEMICAL COMPONENTS 3. Proteins - the most abundant substance next to water, it constitutes 10 to 20% of the cell mass. Two types: A. Structural Proteins (Fibrillar ) - provides the contractile mechanisms of all muscles. B. Global Proteins (mainly enzymes) C. Other type: nucleoproteins of the nucleus that contain DNA which contains the Genes. CHEMICAL COMPONENTS 4. Lipids - the most important lipids are phospholipids and cholesterol which constitutes 2% of the total cell mass. Some cells contain large quantities of triglycerides, also called Neutral Fats. 5. Carbohydrates - most human cell do not maintain large stores of carbohydrates, usually averaging 1% of the total mass.  PHYSICAL STRUCTURES of the cell The cell contains highly organized physical structures called Organelles. 1. Cell Membrane (7.5 - 10 nm) 2. Endoplasmic Reticulum A. Granular Endoplasmic Reticulum - functions for the synthesis of proteins in the cells ( Studded with ribosomes ) B. Agranular Endoplasmic Reticulum or Smooth - functions for the synthesis of lipids substances. 3. Ribosomes - granular particles attached to the outer surfaces of the endoplasmic reticulum and functions for the synthesis of proteins. 4. Golgi Apparatus - functions in association with endoplasmic reticulum in the formation of lysosomes (secretory vesicles) 5. Lysosomes - provides the intracellular digestive system. It allows the cell to digest and remove unwanted substances and structures such as damaged or foreign structures like bacteria. It produce Hydrolases, the enzyme that digest proteins, nucleic acid, mucopolysaccharides, lipids and glycogen. 6. Peroxisomes – physically similar to lysosomes but they are formed by the smooth endoplasmic reticulum. Contain Oxidases, which combines with hydrogen ions to form hydrogen peroxided (H.Os). Most alcohol that a person drinks is detoxified by peroxisomes in the liver. 7. Mitochondria - the "Powerhouses" of the cell. It is composed of two lipid bilayer-protein membranes, outer and inner. 95% of ATP is produced here. 8. Nucleus - the control center of the cell, it controls the chemical reactions that occur in the cell and reproduction of the cell. It contains DNA in large quantities 9. Nucleoli - contains large amount of Ribonucleic Acid and proteins found in the ribosomes. 10. Microfilaments and Microtubular Structures in the Cell - act as Cytoskeleton, providing rigid physical structures for certain parts of the cell. 11.Secretory Vesicles  FUNCTIONAL SYSTEM of the cell 1. Ingestion by the cell (Endocytosis ) Two types: Pinocytosis (Invagination) small particles with fluid Steps: 1. molecules of protein attach to the membrane 2. surface properties of the membrane change in a way that the entire pit invaginates inward 3. the pits borders close are the attachment proteins and extracellular fluid 4. Invaginated portion of membrane breaks away from the surface of the cell forming Pinocytic Vesicles  FUNCTIONAL SYSTEM of the cell Phagocytosis (Evagination) large particle Ingestion of large particles such as bacteria, cells or portions of degenerating tissues 2. Digestion of Foreign Substances in the Cell Immediately after a pinocytic or phagocytic vesicles appear inside a cell, lysosomes release hydrolases and begins hydrolysis of these vesicles. 3. Synthesis and Formation of Cellular Structures by Endoplasmic Reticulum and the Golgi Apparatus A. Formation of proteins by the Granular Endoplasmic Reticulum B. Synthesis of lipids by smooth endoplasmic reticulum C. Processing and formation of intracellular vesicles by the Golgi Apparatus TRANSPORT THROUGH CELL MEMBRANE The fluid inside the cells of the body, called Intracellular Fluid, is different from that outside the cells, called Extracellular Fluid. The extracellular fluid includes both: A. Interstitial Fluid - that circulates in the spaces between the cells. B. Blood Plasma Fluid - that mixes freely with the interstitial fluid through the capillary walls. It is the extracellular fluid that supplies the cells with nutrition and other substances needed for cellular function. Before the cell can utilize these substance, they must be transported through the cell membrane.  THE CONTROL SYSTEM of the Body The human body has thousands of control systems in it. Example of Control System are: A. Regulation of oxygen and carbon dioxide concentrations in the extracellular fluid. B. Regulation of arterial pressure  THE CONTROL SYSTEM of the Body Characteristics of Control System A. Negative Feedback Nature of Control System - this consist of a series of changes that return the factor toward a certain mean value, thus maintaining homeostasis. B. Positive Feedback - Vicious Circles; this does not lead to stability but to instability and often to death. Useful: blood clotting (extravascular), childbirth (contraction of uterus), generation of nerve signals C. Adaptive Control System - feed forward and control CHEMICAL COMPOSITION OF EXTRA AND INTRA CELLULAR FLUIDS Extracellular Intracellular Extracellular Intracellular Na+ 142 mEq/L 10 mEq/L PO2 35 mmHg 20 mmHg K+ 4 mEq/L 140 mEq/L PCO2 46 mmHg 50 mmHg Ca2+ 5 mEq/L 1 mEq/L pH 7.4 7 Mg2+ 3 mEq/L 58 mEq/L Proteins 2 g% 18 g% Cl- 103 mEq/L 1 mEq/L Amino Acids 30 mg% 200 mg% HCO3 28 mEq/L 10 mEq/L Phospholipi 0.5% 2-95% Phosphate 4 mEq/L 78 mEq/L ds SO4 1 mEq/L 2 mEq/L Isotonic 0.9% 0.9% NaCl Glucose 90 mEq/L 0-20 mEq/L  TRANSPORT Transport through the cell membrane, either directly through the lipid bilayer or through the proteins, occur by one or two basic processes: 1. Diffusion or Passive Transport - means random molecular movement of substances either opening the membrane or in combination with a carrier protein caused by kinetic motion of matter. 2. Active Transport - means movement of ions or other substances across the membrane in combination with a carrier protein but additionally against an energy gradient, such as from a low concentration state to a high concentration state, a process that requires chemical energy to cause  TRANSPORT Diffusion Through the Cell Membrane Diffusion through the cell membrane is divided into two separate subprocesses namely: 1. Simple Diffusion - means the molecular kinetic movement of molecules or ions through a membrane opening without the necessity or binding with carrier proteins in the membrane 2. Facilitated Diffusion - means the interaction of the molecules or ions with a carrier protein that aids its passage through the membrane, by binding chemically with fit and shuttling it through the membrane in this form. Pathways of simple Diffusion Through Cell Membrane 1. Diffusion through the lipid Bilayers A. Diffusion of lipid Soluble Substances Lipid soluble substances can pass through the lipid bilayer rapidly examples: oxygen, nitrogen, carbon dioxide, alcohol B. Transport of water and other lipid-insoluble molecules insoluble due to water and lipid(fat) cannot mix examples: water (highly insoluble in lipid membrane) it has great kinetic energy and has small molecules, thereby can penetrate rapidly through the lipid portion Failure ions of to Diffuse Through Lipid Bilayer This layer is impermeable to ions such as sodium, potassium because of the electrical charge which impedes their movement. Causes: 1. Electrical charge of these ions causes water to bond within forming hydrated ions which are very large to penetrate the lipid layer. 2. The electrical charge of the ion interacts with the changes of lipid bilayer. 2. Diffusion through protein channels and Gating of these channels A. They are selectively permeable to certain substances Important channels: 1. Sodium Channels (0.3 x 0,5 nm)- negatively - charged channels 2. Potassium Channels (0.3 x 0.3 nm) - not negatively charged but can allow ions to pass through because their hydrated form are smaller than sodium. B. Many of the channels can be opened or closed by gates These gates provide a means of controlling the permeability of one channel The opening and closing of gates are controlled by these principal ways: 1. Voltage Gating - the molecular conformation of the gate responds to the electrical potential across the cell membrane. Strong negatively inside the cell = gates closed Lost negatively inside the cell = gates open 2. Ligand Gating - some protein channels gates are/opened/by binding another molecule with the protein, this change in protein molecule opens or closes the gate. The molecules that binds is the Ligand Facilitated Diffusion (Carrier - Mediated Diffusion) - the transported substace in this manner/cannot pass through the membrane without specific carrier protein to help it. Substance that cross by facilitated diffusion are: Glucose, Galactose and Amino Acid Factors Affecting net diffusion through protein channels of cell membrane 1. Permeability of membrane 2. Pressure difference across the membrane 3. Difference in concentration of the diffusing substance 4. Electrical potential difference between two sides of membrane Factors affecting the permeability of the membrane 1. Number of channels thru' which substance can diffuse 2. Length of the channels thickness of membrane) 3. The degree of impediment to movement through each channel (lipid solubility) 4. The molecular weight of the diffusing substance 5. Temperature  ACTIVE TRANSPORT - process wherein the cell membrane moves molecules uphill against concentration gradient or against electrical or pressure gradient. Types are as follows: 1. Primary Active Transport - cell volume maintenance energy from ATP. Examples include: maintains the volume of the cell Na-K Pump - the most important transport mechanism in the body that transport sodium out of the cells and pumps potassium from the outside to the inside at the same time. Ca pump H2 ion pump 2. Secondary Active Transport - energy from ionic concentration gradient A. Co-transport Mechanism/Symport 2 substances are transported to the same direction by carrier protein\ Examples: Na - Glucose Costran sport - 2 substances transported in opposite direction B. Counter transport ( Antiport ) Examples: Na - Ca counter transport; Na - hydrogen counter transport C. Uniport transport 1 at a time ( facilitated diffusion) MEMBRANE POTENTIALS AND ACTION POTENTIALS Resting membrane potentials of Nerves 90 millivolts (mv) = resting membrane potential of nerve fibers Nerve Action Potential Nerve signals are transmitted by Action Potential. which are rapid changes in the membrane. The successive stage of the Action Potential: 1. Resting stage (Polarized) 2. Depolarization stage (Na influx) 3. Repolarization stage (Potassium efflux) VOLTAGE - GATED SODIUM AND POTASSIUM CHANNELS PROPAGATION OF THE ACTION POTENTIAL ALL OR NOTHING PRINCIPLE Spike Potential and After-Potentials - Stages: 1. Spike Potential (Depolarization) 2. Negative After-Potential (After-depolarization) the delay of the membrane potential to return to its resting level due the build-up of K ions outside the membrane. This few milliseconds delay is the negative after-potential 3. Positive After-Potential (After-hyperpolarization) a little more negatively the membrane potential return to its normal resting stage Causes: Excess permeability of the nerve membrane to K ions at the end of the spike Electrogenic pumping of excess sodium outward through the nerve fiber Excitation Process of Eliciting Action Potential 1. Chemical Stimulation: stimulation of a nerve fiber by increasing the membrane permeability Examples: acids, bases, salts 2. Mechanical: Crushing, pinching or pricking a nerve fiber can cause action potential due to the sudden surge of sodium influx 3. Electrical Stimulation Chronaxie Action, Potential is elicited this is the time required to stimulate the by introduction of electrical nerve fiber when the voltage is double that of the rheobase current to the fiber which causes excess flow of ions Refractory Period in the axonal membrane a time where a second action potential cannot occur as long as the membrane is Rheobase: defined as the still depolarized from the preceding least possible voltage at action potential which a nerve fiber will Absolute Refractory Period - a time contract wherein a second action potential cannot Utilization Time: the time be elicited even with a very strong stimulus required for the rheobase voltage to stimulate the Relative Refractory Period - a time wherein a strong than normal stimulus nerve fiber can excite the fiber INHIBITION OF EXCITABILITY (STABILIZER AND LOCAL ANESTHETICS) Membrane Stabilizing Factors 1. High extracellular fluid calcium ion concentration 2. Low potassium ion concentration 3. Local anesthetics which prevents opening of Na channels Examples: Cocaine, procaine, etracaine, analgesics  EXCITABLE TISSUES AND MUSCLES OBJECTIVES: 1. Identify and describe the parts of the skeletal muscle 2. Enumerate and explain the types of muscle contractions 3. Differentiate the types of muscle contraction 4. Explain the principle in walk along theory of muscle contraction 5. Outline the sequence of events of muscle contraction as well as the steps in relaxation.  EXCITABLE TISSUES AND MUSCLES 50% of the body is made up of Muscles General Types: 1. Skeletal (voluntary control) comprises the great mass of somatic musculative (10%) it has well-developed cross-striations cannot contract on their own 2. Smooth (Visceral) Involuntary muscle lacks cross-striation found in most hollow viscera can contract on their own 3. Cardiac (Heart) intermediate it has cross-striations like skeletal and is involuntary like smooth muscles contracts rhythmically even in the absence of external stimulus  SKELETAL MUSCLE made up of individual muscle fibers arranged in parallel between the tendinous ends begins and ends in tendons enveloped by a cell membrane called Sarcolemma which consist of a true cell membrane called the plasma membrane. each muscle fiber is made up of myofibrils divided into individual filaments lying side by side. 1 myofibril = 1500 myosin (thick) filaments and 3000 action (thin) filaments  SKELETAL MUSCLE ACTIN FILAMENT Light band I band Composed of: 1. Troponin Strands (protein tropomyosin) - At resting stage, it covers the active sites of actin strands so that interaction with head myosin cannot occur. 2. Troponin Molecule - attached to this molecule are 3 types of troponin. Troponin I - affinity to actin Troponin T - affinity for tropomyosin Troponin C - affinity to calcium which indicates the contraction  SKELETAL MUSCLE MYOSIN FILAMENT Dark band A band has projections at the sides called cross-bridges or myosin heads that link actin and myosin together during contraction  SKELETAL MUSCLE WALK-ALONG THEORY OF MUSCLE CONTRACTION  INITION OF MUSCLE CONTRACTION -EXCITATION CONTRACTIONCOUPLING SEQUENCE OF EVENTS IN CONTRACTION 1. Discharge of motor neuron. 2. Release of transmitter (acetylcholine) nervous system 3. Binding of acetylcholine to acetylcholine receptors (nicotinic acetylcholine) 4. Increased permeability of end-plate membrane to sodium and potassium 5. Generation of end-plate potential 6. Generation of action potential (depolarization) 7. Inward spread of depolarization along the T tubules 8. Release of calcium from lateral sacs of sarcoplasmic reticulum and diffusion to thick and thin filaments 9. Binding of calcium to troponin C,uncovering myosin binding sites 10. Formation of cross-linkages between actin and myosin and sliding of thin and thick filaments,producing shortening or contraction  STEPS IN RELAXATION: 1. Calcium pumped back into sarcoplasmic reticulum 2. Release of calcium from troponin 3. Cessation of interaction between actin and myosin 4. Acetylcholine which started the process will be destroyed by the enzymes in the sarcolemma (acetylcholinesterase)  FACTORS AFFECTING MECHANICAL RESPONSE OF MUSCLES 1. Strength of Stimulus (directly proportional) 2. Length of Sarcomere (Tension) - 2.0 - 2.2 microns (highest degree of contraction) 3. Stretch - too much = less contraction 4. Velocity (Load) inversely proportional - ↑ load = ↓ contraction TYPES OF MUSCLE CONTRACTION 1. Isotonic Contraction (reflexes) requires much sliding among myofibrils (Shortening) contraction lasts longer performs external work has same fusion move limbs in running TYPES OF MUSCLE CONTRACTION 2. Isometric Contraction (Stretch) does not require much sliding of myofibrils (no shortening) same length contraction shorter in duration no work doesn't move load keep limbs stiff when legs hit the ground in running  TYPES OF MUSCLE FIBERS 1. Fast Fibers (Type II) White Muscle muscles that react rapidly Examples: eyes, gastrocnemius, hand muscle 1. Much larger fibers for great strength of contraction 2. Extension sarcoplasmic reticulum for rapid release of Ca ions 3. Large amounts of glycolytic enzyme 4. Less extensive blood supply 5. Fewer mitochondria. Less myoglobin 6. Adapted for rapid 7. Twitch duration 7.5 ms 8. Powerful contraction  TYPES OF MUSCLE FIBERS 2. Slow Fibers (Type 1) Red Muscle muscle that respond slowly but with prolonged period of contraction Examples: soleus, back muscles 1. Smaller fibers 2. Innervated by small nerve fibers 3. More extensive blood supply to extra amount of oxygen 4. Greatly contain large amounts of myoglobin 5. Greater number of mitochondria 6. Prolonged muscle activity - support against gravity 7. Respond slowly 8. Twitch duration - 100 ms Special Features and Abnormalities of Skeletal Muscle Function: 1. Muscle Hypertrophy total muscle mass enlarges in response to contraction of muscles at maximal levels characterized by hyperprasia, the enlargement and splitting of fibers already present in the muscle 2. Muscle Atrophy - occurs when muscles are not used 3.Rigor Mortis (After death) a state of rigidity caused by the loss of ATP which is required in separation of cross bridges from actin muscles remain rigid until the proteins will be destroyed by enzymes released by lysosomes 4. Familiar Periodic Paralysis - due to the decrease in the extracellular fluid potassium occurring periodically 5. Muscle Fibrillation (Fine irregular contractions) Causes: 1. destruction of nerve supply 2. increased sensitivity to circulating acetylcholine 2. Muscle Fasciculation (Jerky, visible contractions) - caused by pathologic discharge of spinal motor neuron  REFERENCES Hall, J. E. (2016). Guyton and Hall textbook of medical physiology (14th ed.). Elsevier. Netter, F. H. (2017). Atlas of human anatomy. Elsevier.