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

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

BiosphereAtoms Molecules Cells Tissues OrgansOrgan

systems OrganismsPopulations of

one speciesEcosystem of

different species

CHEMISTRY

MOLECULARBIOLOGY

CELLBIOLOGY

PHYSIOLOGYECOLOGY

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:Produceschangein variable


Imbalance

Imbalance

Changedetectedby receptor


Receptor (sensor)


Imbalance

Imbalance



Input:Informationsent alongafferentpathway to

Receptor (sensor)


Controlcenter

Imbalance

Imbalance




Receptor (sensor) Effector


Output:Information sentalong efferentpathway to activate

Controlcenter

Imbalance

Imbalance




Receptor (sensor) Effector


Response ofeffector feedsback toinfluencemagnitude ofstimulus andreturns variableto homeostasis

Output:Information sentalong efferentpathway to activate

Controlcenter

Imbalance

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

Intracellularfluid of

most cells

Material entersand leavesthe body

Material entersand leaves

the body

External environmentof 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 inhomeostasis

Externalchange

Internal changeresults in

loss of homeostasis

Compensation succeedsCompensation fails

WellnessIllness or disease

Organism attemptsto compensate

Internalchange

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

Inputsignal

OutputsignalController

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 MapsPerson workingoutside on a hot,

dry day

Loses body waterby evaporation

Body fluids becomemore concentrated

Thirst pathwaysstimulated

Person seeks outand drinks water

Internal receptorssense change in

internal concentration

Water addedto body fluids

decreases theirconcentration

(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: 37oC (98.6oF)

– Hypothermia = decrease in body temperature– Hyperthermia = increase in body temperature• above 41oC, dangerous• above 43oC, 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

25-30oC– 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

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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