Lecture 1: Introduction to Physiology and Homeostasis PDF

Lecture 1: Introduction to Physiology and Homeostasis BIOL 310 Dr. K  Course Introduction Textbook: Human Physiology: From Cells to Systems, 9th Edition by Lauralee Sherwood. Cengage Learning, 2016 Introdu...

Lecture 1: Introduction to Physiology and Homeostasis BIOL 310 Dr. K  Course Introduction Textbook: Human Physiology: From Cells to Systems, 9th Edition by Lauralee Sherwood. Cengage Learning, 2016 Introductory course in the functions and mechanisms of the human body Learn concepts and facts relevant to homeostasis, intercellular communication and signal transduction Understand human body both structural and functional points of view Understand relationship between various anatomical structures Utilize simple clinical tests to determine disease states  Physiology Tips Foundation of medicine Learning physiology has long-lasting, downstream effects for understanding pathology and clinical medicine ☤ All health care professionals must comprehend basic physiological principles to be able to understand what’s happening in the body when things go wrong and to determine what needs to be done to correct the situation The best way to get the normal processes in mind is by integrating them with abnormal physiology Cannot be memorized, must be understood! Physiology focuses on concepts, principles and interconnections rather than isolated facts  What is Expected ★ Visit Canvas daily ☺ Slides posted prior to lecture class ☺ Helpful study resources ☺ Pay attention to important dates in lecture schedule ★ Highly recommended to strengthen your understanding in physiology: ✓ Set goals (plan of attack) at beginning of semester ✓ Pre- and post- read lecture slides (repetition is key!) ✓ Actively participate and take notes during lecture ✓ Keep up with assigned chapters ✓ Do practice questions early and often ✓ Flowcharts/diagrams ✓ Effective time management skills ✓ Take breaks from any study material (Rule of thumb: 10 min break for every hour of studying)  What is Expected ★ Attendance is mandatory ★ Grading scheme:  4 non-cumulative exams = 65% 50 – 60 multiple choice questions  Participation/Attendance = 10%  Laboratory = 25% ★ Zero tolerance for cheating ★ If you have any questions or problems, seek advice of professor as early in the semester as possible  Introduction to Physiology Physiology Study of the functions of living things 2 approaches to explain body functions: Emphasis on purpose of body process (Why?) Explanations are in terms of meeting a bodily need Emphasis on mechanism (How?) Explanations are in terms of cause and effect sequences Physiology is closely related to Anatomy Study of structure of body Physiological mechanisms are possible through structural design  Levels of Organization in the Body Body is structurally organized into a total functional unit Chemical Cellular Tissue Organ Body system Organism  Levels of Organization in Body Chemical level Various atoms and molecules make up body Atoms: mostly oxygen, carbon, hydrogen, and nitrogen Molecules of life: proteins, carbohydrates, fats, and nucleic acids (genetic material, such as deoxyribonucleic acid, or DNA) Cellular level Cells are basic units of life Have basic and specialized functions Basic functions = individual cell survival Specialized functions = survival of whole body Organisms can be single-celled or multicellular Cells differentiate in complex multicellular organisms  Basic Cell Functions Essential for survival of individual cells Obtain nutrients and oxygen from surrounding environment Perform chemical reactions that provide energy for cell Food + O2  CO2 + H2O + energy Eliminate CO2 and other wastes to surrounding environment Synthesize needed cellular components Control exchange of materials between cell and its surrounding environment Sensing and responding to changes in surrounding environment Reproduction Exception: nerve cells and muscle cells lose their ability to reproduce during their early development  Specialized Cell Functions Modification of basic function essential for survival of whole body Gland cells of digestive system secrete digestive enzymes that break down ingested food Kidney cells selectively retain substances needed by body and eliminate unwanted substances in urine Muscle cells produce intracellular movement to generate tension and contract muscles Nerve cells generate and transmit  Level of Organization in the Body Tissue level Tissues: group of cells with similar structure and specialized function 4 primary types: 1. Muscle tissue = skeletal, cardiac, and smooth 2. Nervous tissue = initiate and transmit electrical impulses In brain, spinal cord and nerves 3. Epithelial tissue = exchange materials between cell and environment 4. Connective tissue = connects, supports, and anchors various body parts E.g. tendons, bones, cartilage, blood Organ level 2 or more types of primary tissues that function together to perform a particular function(s)  Level of Organization in Body Organ system level Groups of organs that perform related functions and interact to accomplish a common activity essential to survival of whole body 11 systems: Circulatory, digestive, respiratory, urinary, skeletal, muscular, integumentary, immune, nervous, endocrine, and reproductive Organism level Body systems are packaged into a functional whole body Each body system depends on proper functioning of other systems Many complex body processes depend on interplay among multiple systems  Why is it important to study each level of structural organization ? a) The organization at each level determines structural characteristics of higher levels. b) The organization at each level determines functions of higher levels. c) A and B are correct answers. d) It is not relevant to study all levels of organization.  Homeostasis Maintenance of a relatively stable internal environment Physiological variables are in a state of dynamic constancy Continuous changes that occur are minimized by compensatory physiological responses Body is still in overall balance Essential for survival and function of all cells Body cells are contained in watery internal environment through which life- sustaining exchanges are made Surrounding external environment is where an organism lives  The Internal Environment Extracellular fluid (ECF) Fluid surrounding cells 2 components: Plasma (20-25% of ECF)- fluid portion of blood Interstitial fluid (75-80% of ECF)- lies around and between cells Intracellular fluid (ICF) Fluid inside cells 67% of all fluid in body Body cells can live and function only when ECF is compatible with their survival Chemical composition and physical state of internal environment is important for cells to regulate their own activity  Homeostasis Blood glucose levels increase after eating Levels return to their set point via homeostasis Example of dynamic constancy – Levels change over short periods of time, but remain relatively  Interdependence of Cells, Body Systems and Homeostasis Homeostasis is essential for survival of each cell Each cell through its specialized activities as part of an organ system help maintain internal environment shared by all cells Functions performed by each organ system contribute to homeostasis Maintain within body the environment required for survival and function of all cells  Homeostasis Factors homeostatically regulated: Concentration of nutrients Constant supply needed for energy production Concentration of O2 and CO2 O2 needed for chemical reactions CO2 produced must be removed Concentration of waste products Removed to avoid toxic effect on body cells Changes in pH Enzymes are pH-dependent Concentrations of water, salt, and other electrolytes Influences how much water enters or leaves cell Volume and pressure Ensure body-wide distribution Temperature Cell function is temperature-dependent Body System Contributions to Homeostasis Circulatory system (heart, blood vessels and blood) Carries materials from one part of body to another Digestive system (mouth, esophagus, stomach, intestines and related organs) Breaks down dietary food into smaller molecules that can be distributed/absorbed into body cells Transfers water and electrolytes from external environment to internal environment Eliminates undigested food residues to external environment in the feces Respiratory system (lungs and airways) Gets O2 from and eliminates CO2 to external environment Important in maintenance of proper pH of internal environment Body System Contributions to Homeostasis Urinary system (kidneys, bladder, ureters, urethra) Removes excess water, salt, acid, and other electrolytes from plasma and eliminates them in urine Skeletal system (bones and joints) Provides support and protection for soft tissues and organs Serves as storage reservoir for calcium Along with muscular system enables movement of body and its parts Bone marrow is source of all blood cells Muscular system (skeletal muscles) Moves bones Generates heat and maintains body temperature  Body System Contributions to Homeostasis Integumentary system (skin) Serves as outer protective barrier Important in regulating body temperature Immune system (white blood cells, lymphoid organs) Defends against foreign invaders and against body cells that have become cancerous Helps in repairing or replacing injured or worn-out cells Nervous system (brain, spinal cord, nerves and sense organs) Controls and coordinates bodily activities that require rapid responses Detects and initiates reactions to changes in external environment Body System Contributions to Homeostasis Endocrine system (all hormone- secreting glands) Secreting glands of endocrine regulate activities that require duration rather than speed Controls concentration of nutrients and by adjusting kidney function, controls internal environment’s volume and electrolyte composition Reproductive system (male and female gonads and related organs) Not essential for homeostasis (not essential  Homeostatic Control Systems An interconnected network of body components Operates to maintain a given factor in the internal environment at a relatively constant optimal level To maintain homeostasis, control system must be able to: 1. Detect deviations from normal in internal environment 2. Integrate this information with other relevant information 3. Make appropriate adjustments in activity of body parts responsible for restoring factor to its desired value (normal)  Homeostatic Control Systems Grouped into 2 classes: 1. Intrinsic (local) controls Built into an organ Autoregulation 2. Extrinsic (systemic) controls Initiated outside an organ to alter organ’s activity Accomplished by nervous and endocrine systems Permits coordinated regulation of several organs toward a common goal Feedback systems are a common mechanism to control physiological processes Bring about a reaction to a change in a regulated variable 2 common types: Negative feedback system Positive feedback system  Which of these statements describe(s) extrinsic regulation? a) Extrinsic regulation results from the activities of the nervous system or endocrine system. b) Extrinsic regulation adjusts activities automatically in response to some environmental change. c) Extrinsic regulatory mechanisms involve oxygen levels declining in a tissue that would promote local vasodilation. d) Statements B and C are correct.  Homeostatic Control Systems Negative feedback Primary type of homeostatic control Response opposes initial change Corrective response/adjustment Restore initial value (set point) Control system’s output is regulated to resist change Body moves back to homeostasis Components: Receptor (sensor) Monitors magnitude of a controlled variable Control center (integrator) Compares sensor’s input with a set point and makes adjustments to bring about appropriate response to oppose deviation from set point Effector Executes response to produce desired effect (corrects initial change)  Homeostatic Control Systems Reflex A specific, involuntary, unpremeditated, “built-in” response to a particular stimulus E.g. pulling your hand away from a hot object or shutting your eyes as an object rapidly approaches your face Reflex arc A pathway mediating a reflex Components: Stimulus Receptor Afferent (incoming) pathway Integrating center (CNS-spinal cord, brain) Efferent (outgoing) pathway Effector  Reflex Arc Stimulus Detectable change in internal or external environment Receptor Detects environmental change Afferent (sensory) pathway Incoming signal travels from receptor to integration center Efferent (motor) pathway Outgoing information going from integration center to effector Effector Executes response Most commonly- muscles and glands (secrete hormones) Negativ e Feedbac k When we get cold, our body compensates by shivering. In this example, what role do the muscles play? a) Receptors b) Control centers c) Stimuli d) Effectors  Homeostatic Control Systems Positive feedback Initial stimulus produces an effector response that enhances or amplifies initial change Body is moved away from homeostasis Controlled variable continues to move in direction of initial change Normal range is not maintained Found when a potentially dangerous or stressful process must be completed quickly to restore homeostasis Exs: Immediate danger from a severe cut is loss of blood → decrease BP and reduce efficiency of heart Body’s response to blood loss is blood clot formation Stimulate recruitment of more platelets Labor and delivery Oxytocin cause powerful uterine contractions Uterine contractions push baby against cervix causing cervix to stretch triggering release of more oxytocin Uterine contractions become increasingly stronger until birth of baby  Homeostatic Control Systems Feedforward mechanism Initiate responses in anticipation of a change in a regulated variable Not commonly used E.g. Biological rhythms Enable homeostatic mechanisms to be used immediately and automatically by activating them at times when a challenge is likely to occur but before it does occur E.g. circadian rhythm, body temperature and hormone concentrations in blood Insulin levels increase while a meal is in digestive tract Anticipatory response to limit rise in blood nutrient concentration after nutrients are absorbed Site, smell and thought of food triggers cells of digestive tract to prepare it for arrival of food Increase saliva, stomach churns and produces acid Disruptions in Homeostasis Organ system(s) malfunction and cells no longer have optimal environment in which to live and function Lead to illness and death When homeostasis is maintained, we refer to physiology; when it is not, we refer to pathophysiology Pathophysiology = abnormal functioning of body (altered physiology) associated with disease When a homeostatic disruption becomes so severe that it is no longer compatible with survival, death results What part of a homeostatic mechanism senses an environmental stimulus? a) Effector b) Responder c) Receptor d) Sensor  Clinical Case A 64-year-old, fair-skinned man in good overall health spent a very hot, humid summer day gardening in his backyard. After several hours in sun, he began to feel light-headed and confused as he knelt over his vegetable garden. Although earlier he had been perspiring profusely and appeared flushed, his sweating had eventually stopped. Because he also felt confused and disoriented, he could not recall for how long he had not been perspiring, or even how long it had been since he had taken a drink of water. He called to his wife, who was alarmed to see that his skin had turned a pale-blue color. She asked her husband to come indoors, but he fainted as soon as he tried to stand. Wife called for an ambulance, and man was taken to a hospital and diagnosed with a condition called heatstroke. 1. What happened to this man that would explain his condition? Patient is gardening on a hot, humid day → body temperature increases Initially, skin blood vessels dilate, making him appear flushed and helping him dissipate heat across his skin Also, he perspired heavily Perspiration is an important mechanism by which the body loses heat Results in a more concentrated ECF → imbalance in ion concentrations in body fluids 2. How does the man’s condition relate to homeostasis? Fluid in sweat comes from ECF compartment With profuse sweating ECF levels decrease → blood pressure to decrease Hence patient feeling light-headed As BP decreased, ability for heart to pump sufficient blood against gravity up to his brain also decreased When brain cells are deprived of blood flow, they begin to malfunction → decrease in mental function → confusion  Clinical Case Sequence of events in heatstroke: Increased body temperature → Sweating Deceased body fluid volume Decreased blood pressure Vasoconstriction of skin blood vessels Causes decreased heat loss and sweating → increased body temperature of heatstroke Treatment (Tx): Intravenous fluids (IVFs) made up of an isotonic salt solution to restore his fluid levels and concentrations Immersion in a cool bath and cool compresses to help reduce body temperature