Physiology M.Ilker Gelisen MD

Agenda What is physiology? From cell to human (levels of organization) A review of the organ systems Introduction of the concept of homeostasis Themes in Physiology

Physiology – Study of the normal functioning of a living organism and its component parts Physiology is the study of the normal function of cell, tissue, organs, systems and organisms

Physiology can be divided into the following specialties: – Cell physiology – study of cell – Special physiology - study of specific organ – Systemic physiology – study of system – Pathological physiology (Pathophysiology) – study of the effect of disease on cell, tissue, organ and system. The Specialties of Physiology

Levels of Organization BiosphereAtomsMoleculesCellsTissuesOrgans Organ systems Organisms Populations of one species Ecosystem of different species CHEMISTRY MOLECULAR BIOLOGY CELL BIOLOGY PHYSIOLOGY ECOLOGY

Levels of Organization

Levels of Organization - Human

Organ Systems in Review Integumentary Musculoskeletal Respiratory Digestive Urinary Reproductive Circulatory / Cardiovascular Nervous Endocrine Lymphatic / Immune Protection from environmental hazards; temperature control Support, protection of soft tissues; mineral storage; blood formation Locomotion, support, heat production Directing immediate responses to stimuli, usually by coordinating the activities of other organ systems Directing long-term changes in the activities of other organ systems Internal transport of cells and dissolved materials, including nutrients, wastes, and gases Defense against infection and disease Delivery of air to sites where gas exchange can occur between the air and circulating blood Processing of food and absorption of organic nutrients, minerals, vitamins, and water Elimination of excess water, salts, and waste products; control of pH Production of sex cells and hormones Organ System Major Functions Integumentary system Skeletal system Muscular system Nervous system Endocrine system Cardiovascular system Lymphatic system Respiratory system Digestive system Urinary system Reproductive system

Human Body

Interrelationships Among Body Systems

Necessary Life Functions Maintain boundaries Movement – Locomotion – Movement of substances Responsiveness – Ability to sense changes and react Digestion – Break-down and absorption of nutrients

Necessary Life Functions Metabolism—chemical reactions within the body – Produces energy – Makes body structures Excretion – Eliminates waste from metabolic reactions

Necessary Life Functions Reproduction – Produces future generation Growth – Increases cell size and number of cells

Survival Needs Water – 60 of body weight – Provides for metabolic reaction Stable body temperature Atmospheric pressure – Must be appropriate

Survival Needs Nutrients – Chemicals for energy and cell building – Includes carbohydrates, proteins, lipids, vitamins, and minerals Oxygen – Required for chemical reactions

Homeostasis X Homeostasis—maintenance of a stable internal environment – A dynamic state of equilibrium Homeostasis is necessary for normal body functioning and to sustain life Homeostatic imbalance – A disturbance in homeostasis resulting in disease

Key Themes in Physiology: 1. Homeostasis (Body systems work together (Integration of function) Internal vs. external failure of homeostasis 2.Communication and movement across cell membranes Vital to integration & homeostasis Cells communicate with other cells, tissues & organs

A homeostatic regulatory mechanism consist of : – A receptor – senses an environmental change or stimuli. – A control center –processes information supplied by receptor and generates a response (command) – An effector – an organ or cell that responds to the command of control center. A variation outside the desired range triggers an automatic response to correct the situation – Negative feedback Homeostatic regulation

Maintaining Homeostasis The body communicates through neural and hormonal control systems – Receptor Responds to changes in the environment (stimuli) Sends information to control center

Maintaining Homeostasis – Control center Determines set point Analyzes information Determines appropriate response – Effector Provides a means for response to the stimulus

Feedback Mechanisms Negative feedback – Includes most homeostatic control mechanisms – Shuts off the original stimulus, or reduces its intensity – Works like a household thermostat

In positive feedback an initial stimulus produces a response that enhances the change in the original condition. For instance: Damage to blood vessel wall will cause release of chemicals. Chemicals will trigger blood clotting Clotting process increases release of chemicals More chemicals means accelerated clotting Accelerated clotting means more chemicals

Homeostasis

Variable (in homeostasis)

Stimulus: Produces change in variable Variable (in homeostasis) Imbalance

Change detected by receptor Stimulus: Produces change in variable Receptor (sensor) Variable (in homeostasis) Imbalance

Change detected by receptor Stimulus: Produces change in variable Input: Information sent along afferent pathway to Receptor (sensor) Variable (in homeostasis) Control center Imbalance

Change detected by receptor Stimulus: Produces change in variable Input: Information sent along afferent pathway to Receptor (sensor) Effector Variable (in homeostasis) Output: Information sent along efferent pathway to activate Control center Imbalance

Change detected by receptor Stimulus: Produces change in variable Input: Information sent along afferent pathway to Receptor (sensor) Effector Variable (in homeostasis) Response of effector feeds back to influence magnitude of stimulus and returns variable to homeostasis Output: Information sent along efferent pathway to activate Control center Imbalance

Negative Feedback: The Control of Body Temperature

Feedback Mechanisms Positive feedback – Increases the original stimulus to push the variable further – In the body this only occurs in blood clotting and during the birth of a baby

Function versus Process Function explains the “why” – Teleological approach Process or mechanism describes the “how” – Mechanistic approach Red blood cell example – “Because cells need oxygen and red blood cells bring it to them.” – “Oxygen binds to hemoglobin molecules contained in the red blood cells.”

Homeostasis – Most cells contact extracellular fluid – Out out – Out – In – In in Extracellular fluid: the internal environment of the body Intracellular fluid of most cells Material enters and leaves the body Material enters and leaves the body External environment of the body

Homeostasis and Controls External or internal change Loss of homeostasis – Sensed by organism Physiological attempt to correct Negative feedback loop

Homeostasis and Controls Successful compensation – Homeostasis reestablished Failure to compensate – Illness – Death Study of failure to compensate is pathophysiology

Organism in homeostasis External change Internal change results in loss of homeostasis Compensation succeedsCompensation fails WellnessIllness or disease Organism attempts to compensate Internal change Homeostasis and Controls

Themes in Physiology Homeostasis – Control systems Biological energy use Structure-function relationships – Molecular interactions – Mechanical properties of cells, tissues, and organs Communication – Chemical and electrical signals

Themes in Physiology A simple control system Input signal Output signal Controller

Concept Mapping Organizational tool for relationships and processes Schematic diagram of structure and function – Cells, tissues, and organs Flow charts – Diagram processes in sequence

Concept Mapping: Types of Maps Person working outside on a hot, dry day Loses body water by evaporation Body fluids become more concentrated Thirst pathways stimulated Person seeks out and drinks water Internal receptors sense change in internal concentration Water added to body fluids decreases their concentration (b) A process map, or flow chart

Homeostasis Process of maintaining stable internal environment compatible for life – Most organ systems contribute to homeostasis – Exception: reproductive system

Negative Feedback Control in Homeostasis – Primary mechanism for maintaining homeostasis – External change  triggers change in regulated variable in internal environment  triggers reaction to oppose the change and return regulated variable toward normal (set point)

Negative Feedback Mechanisms – Set point = desired level of regulated variable – Sensors detect level of regulated variable and provide input to integrating center – Integrating center compares set point to actual level of regulated variable – Error signal = difference between actual level and set point – Integrating center sends output to effectors to return regulated variable toward set point

Negative Feedback Control of Car Speed

Negative Feedback Control of Body Temperature

Negative Feedback Loop

Positive Feedback Loop Positive feedback loops cause a rapid change in a variable.

Thermoregulation – Homeothermic animals – regulate body temperature within a narrow range – Poikilothermic animals – do not regulate body temperature

Homeothermic Animals – Normal body temperature = set point Differs in animal species Humans: 37 o C (98.6 o F) – Hypothermia = decrease in body temperature – Hyperthermia = increase in body temperature above 41 o C, dangerous above 43 o C, deadly

Mechanisms of Heat Transfer Between Body and External Environment – Radiation - thermal energy as electromagnetic waves – Conduction - thermal energy through contact – Evaporation - heat loss through evaporation of water insensible water loss sweating – Convection - heat transfer by movement of fluid or air

Components of Thermoregulatory System – Thermoregulatory system maintains core body temperature – Detectors - thermoreceptors (central and peripheral) – Integrator - hypothalamus – Effectors - sweat glands, blood vessels in skin, skeletal muscles

Thermoneutral Zone Range of outside temperature where alterations in blood flow alone regulates body temperature o C – Body temperature increase: blood flow to skin increases – Body temperature decrease: blood flow to skin decreases

Negative Feedback Control of Body Temperature

Thermoregulation

Fever – Fever accompanies infections – White blood cells secrete pyrogens – Body temperature set point increases – Fever enhances immune response

Teşekkür ederim