pengantar homeostasis

HomeostasisHomeostasis

M. Djauhari WidjajakusumahM. Djauhari Widjajakusumah

Departmen FisiologiDepartmen FisiologiFakultas Kedokteran Universitas IndonesiaFakultas Kedokteran Universitas Indonesia

Human Physiology Human Physiology

o Concerns with the Concerns with the specific characteristics and specific characteristics and mechanisms of the human bodymechanisms of the human body that make it a that make it a living beingliving being

o Encompasses all aspects of human biology, it is Encompasses all aspects of human biology, it is the study of the function of human bodythe study of the function of human body which which is inseparable from its structureis inseparable from its structure

Guyton and Hall: Textbook of Medical Physiology 11th ed. 2006Guyton and Hall: Textbook of Medical Physiology 11th ed. 2006

Cell, The Basic Unit of LifeCell, The Basic Unit of Lifeo The basic unit of both structure and function in living The basic unit of both structure and function in living

being. The smallest unit capable of carrying out processes being. The smallest unit capable of carrying out processes associated with life.associated with life.

o Each type of cell is specially adapted to perform one Each type of cell is specially adapted to perform one particular function. particular function.

o All cells have certain basic characteristics that are alike. All cells have certain basic characteristics that are alike. Oxygen combines with macronutrients to release energyOxygen combines with macronutrients to release energy Cells deliver end-products of the chemical reactions into Cells deliver end-products of the chemical reactions into

the interstitial fluids. the interstitial fluids. Almost all cells have the ability to reproduce. Almost all cells have the ability to reproduce. Cells consist of chemical components (atoms: oxygen, Cells consist of chemical components (atoms: oxygen,

carbon, hydrogen, nitrogen carbon, hydrogen, nitrogen molecules: protein, molecules: protein, carbohydrate, fat, nucleic acids [DNA genetic materials]) carbohydrate, fat, nucleic acids [DNA genetic materials])

o Organ is an aggregate of many different cells held Organ is an aggregate of many different cells held together by intercellular supporting structures.together by intercellular supporting structures.


Basic Cell Functions Essential for Survival Basic Cell Functions Essential for Survival of the Cellof the Cell

1. Obtaining nutrients and oxygen from the surrounding environment1. Obtaining nutrients and oxygen from the surrounding environment2. Utilizing nutrients (carbohydrate, fat, protein) and oxygen by way 2. Utilizing nutrients (carbohydrate, fat, protein) and oxygen by way ofof performing various chemical reactions to provide energy for the performing various chemical reactions to provide energy for the cells.cells.3. Eliminating CO2 and other by products, wastes produced during3. Eliminating CO2 and other by products, wastes produced during

chemical reactions, to the surrounding of the cellschemical reactions, to the surrounding of the cells4. Synthesizing protein & other components 4. Synthesizing protein & other components cellular structure, cellular structure, growth, growth,

carrying out cell functionscarrying out cell functions5. Controlling materials exchange between the cell and its 5. Controlling materials exchange between the cell and its surrounding surrounding environmentenvironment6. Moving materials from one part of the cell to another in carrying 6. Moving materials from one part of the cell to another in carrying outout

cellular activitiescellular activities7. Being sensitive and responsive to changes in the surrounding 7. Being sensitive and responsive to changes in the surrounding

environmentenvironment8. Reproducing, in most cells8. Reproducing, in most cells

Intercellular CommunicationIntercellular CommunicationCells communicate with each other Cells communicate with each other via chemical messengervia chemical messenger

• Gap junctionGap junctionChemical messenger move from cell to cell without Chemical messenger move from cell to cell without entering ECFentering ECF

• Neural communicationNeural communicationNeurotransmitter released from nerve cells at synaptic Neurotransmitter released from nerve cells at synaptic junction, act across synaptic cleft on postsynaptic celljunction, act across synaptic cleft on postsynaptic cell

• Endocrine communicationEndocrine communicationHormones reach and bind to receptors of the target cells Hormones reach and bind to receptors of the target cells via the circulating bloodvia the circulating blood

• Paracrine communicationParacrine communicationProducts of cells diffuse in the ECF to affect neighboring Products of cells diffuse in the ECF to affect neighboring cells cells

• Autocrine communicationAutocrine communicationChemical messenger secreted by cell, bind to receptors on Chemical messenger secreted by cell, bind to receptors on the same cell, i.e. the cell that secreted the messengerthe same cell, i.e. the cell that secreted the messenger

Intercellular communication by chemical Intercellular communication by chemical mediatorsmediators

Body FluidsBody Fluidso 56-60% of the adult human being is fluid. 56-60% of the adult human being is fluid. o 2/3 of this fluid is the intracellular fluid (40% bw) 2/3 of this fluid is the intracellular fluid (40% bw)

1/3 of this fluid is the extracellular fluid (20% bw) 1/3 of this fluid is the extracellular fluid (20% bw) o Claude Bernard Claude Bernard (the 19(the 19thth century French physiologist): century French physiologist):

Extracellular fluid is the internal environment of the Extracellular fluid is the internal environment of the body body (millieu interieur) (millieu interieur) that contains - among others - that contains - among others - the ions and nutrients needed by the cells for the the ions and nutrients needed by the cells for the maintenance of the cellular life maintenance of the cellular life homeostasis homeostasis

Body fluid compartments. Arrows represent fluid movement. Transcellular fluids, which constitute a very small percentage of total body fluids, are not shown. William F. Ganong: Review of Medical Physiology 22nd ed, 2005

Extracellular Fluid (ECF)Extracellular Fluid (ECF)o Constantly moves throughout the body Constantly moves throughout the body o Rapidly transported in the circulating blood Rapidly transported in the circulating blood

(intravascular fluid)(intravascular fluid)o Fluid exchange between the intravascular and the Fluid exchange between the intravascular and the

tissue (interstitial) fluids by way of diffusion through tissue (interstitial) fluids by way of diffusion through the capillary wallsthe capillary walls

o ECF contents: ECF contents: Na, K, Ca, Cl, and bicarbonate ionsNa, K, Ca, Cl, and bicarbonate ions Nutrients (O2, glucose, fatty acids, amino acids)Nutrients (O2, glucose, fatty acids, amino acids) CO2, transported from the cells to the lungs CO2, transported from the cells to the lungs Other cellular productsOther cellular products

Constituents and Physical Characteristics of the ECFConstituents and Physical Characteristics of the ECF


HomeostasisHomeostasis•Homeo Homeo == same; same; statis statis == constantconstant

•The maintenance of The maintenance of nearly constant conditions in nearly constant conditions in the internal environment the internal environment (milieu interieur) (milieu interieur)

•An active processAn active process through which the constancy through which the constancy of components of the immediate environment of of components of the immediate environment of the cell is maintained within the physiological the cell is maintained within the physiological range within which life can surviverange within which life can survive

•Not an unchanging or static state; it is Not an unchanging or static state; it is a dynamic a dynamic state,state, it changes according to the changing it changes according to the changing needs of the body needs of the body short term or long term short term or long term adaptationsadaptations

•Homeodynamic Homeodynamic would be the better word would be the better word A A dynamic steady state in the internal environmentdynamic steady state in the internal environment


• The activities of cells, tissues, and organs The activities of cells, tissues, and organs must be regulated and integrated with each must be regulated and integrated with each other in such a way that other in such a way that any change in the any change in the extracellular fluid initiates a reaction to extracellular fluid initiates a reaction to minimize the change. minimize the change.

• HomeostasisHomeostasis denotes the denotes the relatively relatively stable stable conditions of the internal environmentconditions of the internal environment that that result from these compensating regulatory result from these compensating regulatory responses performed by responses performed by homeostatic homeostatic control systems.control systems.

Vander et al.: Human Physiology: The Mechanism of Body Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition, © The McGraw−HillFunction, Eighth Edition, © The McGraw−Hill

Companies, 2001Companies, 2001


• Cell survival depends on Cell survival depends on maintenance of a maintenance of a relative stable internal fluid environment (ECF)relative stable internal fluid environment (ECF) with which cells directly make self-sustaining with which cells directly make self-sustaining exchangesexchanges

• The cells continue to live and function properly The cells continue to live and function properly providing the normal condition of the internal providing the normal condition of the internal environment is maintainedenvironment is maintained

• Homeostasis is essential for each cell’s survival, Homeostasis is essential for each cell’s survival, each cell benefits from homeostasis. each cell benefits from homeostasis.

• Each cell contributes its share towards the Each cell contributes its share towards the maintenance of homeostasis. maintenance of homeostasis.

HomeostasisHomeostasis• The body systems’ functions are to maintain homeostasisThe body systems’ functions are to maintain homeostasis; ;

and depend on the specialized activities of the cellsand depend on the specialized activities of the cells• The internal environment factors that The internal environment factors that must be must be

homeostatically maintained homeostatically maintained are:are: concentration of nutrient molecules, O2 and CO2, concentration of nutrient molecules, O2 and CO2,

waste products, water, salt, and other electrolytes waste products, water, salt, and other electrolytes pHpH temperaturetemperature volume and pressurevolume and pressure

• Each functional structure / organ provides its share in the Each functional structure / organ provides its share in the maintenance of homeostatic conditions maintenance of homeostatic conditions in the internal in the internal environment (ECS):environment (ECS): Lungs provide O2 to replenish O2 being used by the cellsLungs provide O2 to replenish O2 being used by the cells Kidneys maintain constant ion concentrationsKidneys maintain constant ion concentrations GI system provides nutrientsGI system provides nutrients

Disruption of Homeostatic conditionDisruption of Homeostatic condition

• One or more functional systems lose their ability One or more functional systems lose their ability to contribute their share of function to contribute their share of function cells of cells of the body suffer. the body suffer.

• Extreme dysfunction leads to death, whereas Extreme dysfunction leads to death, whereas moderate dysfunction leads to sickness. moderate dysfunction leads to sickness.

Regulation of Body FunctionsRegulation of Body FunctionsThe Nervous SystemThe Nervous System

Provides rapid coordinationsProvides rapid coordinations of internal organ of internal organ system, and response to the external environment to system, and response to the external environment to maintain the homeostatic condition. maintain the homeostatic condition.

Interactions between the nervous and endocrine Interactions between the nervous and endocrine controlling systems controlling systems are precisely adjusted by are precisely adjusted by complex mechanism complex mechanism the neuroendocrine the neuroendocrine regulation. regulation.

Regulation of Body FunctionsRegulation of Body FunctionsThe Nervous SystemThe Nervous System

Composed of three major partsComposed of three major partso The sensory input portionThe sensory input portion

Sensory receptors detect the state of the body or the Sensory receptors detect the state of the body or the state of the surroundingsstate of the surroundings

o The central nervous system (CNS)/integrative portionThe central nervous system (CNS)/integrative portionComposed of the brain, the brain stem, and the spinal Composed of the brain, the brain stem, and the spinal cord.cord.The brain stores information, generate thoughts, The brain stores information, generate thoughts, determines reactions in response to the sensory inputs. determines reactions in response to the sensory inputs.

o The motor output portionThe motor output portionTransmits appropriate signals from CNS to carry out Transmits appropriate signals from CNS to carry out appropriate responsesappropriate responses

Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition

© The McGraw−Hill Companies, 2001© The McGraw−Hill Companies, 2001

Regulation of Body FunctionsRegulation of Body FunctionsThe Endocrine SystemThe Endocrine System

o Hormones are transported in the ECF to all Hormones are transported in the ECF to all parts of the body to help regulate cellular parts of the body to help regulate cellular functionsfunctions

o Complements the nervous system Complements the nervous system o The nervous system regulates mainly the The nervous system regulates mainly the

muscular and secretory activities, muscular and secretory activities, the the hormonal system regulates mainly the hormonal system regulates mainly the metabolic functions.metabolic functions.

The Control System of The Body The Control System of The Body

• Proportional control system: Proportional control system: Adjusting and reacting Adjusting and reacting (giving response) (giving response) to to changes in thechanges in the environment environment (stimuli)(stimuli) in in proportion to the degree of fluctuation of the proportion to the degree of fluctuation of the controlled variables.controlled variables.

• A complex and integrated system.A complex and integrated system.Simple proportional system still has minor Simple proportional system still has minor errors that can be corrected by an integral errors that can be corrected by an integral control system.control system.

The Control System of The Body The Control System of The Body

• Intracellular control systemIntracellular control system Genetic control system, controls intracellular Genetic control system, controls intracellular

functionsfunctions

• Organ level control system (intrinsic /local control Organ level control system (intrinsic /local control system)system) Controls the functions of parts of the organ Controls the functions of parts of the organ

• Inter organ control system (extrinsic control system)Inter organ control system (extrinsic control system) Operates throughout the entire body to control the Operates throughout the entire body to control the

interrelationships among organsinterrelationships among organsThe respiratory system regulates the The respiratory system regulates the

concentration of CO2, in association with the concentration of CO2, in association with the nervous systemnervous system

The liver and pancreas regulate the The liver and pancreas regulate the concentration of blood glucoseconcentration of blood glucose

Characteristics of Control System – Characteristics of Control System – Feedback mechanismsFeedback mechanisms

Feedback systemFeedback systemFeedback: responses made after a change has been Feedback: responses made after a change has been detecteddetectedFeedback system generally operate on the principle Feedback system generally operate on the principle ofof negative feed back:negative feed back:

Negative feedback systemNegative feedback systemIntegrative system that measures and compares Integrative system that measures and compares

the input and the input and output, and gives responseoutput, and gives response to any to any discrepancy to maintain a discrepancy to maintain a biological system in a biological system in a steady statesteady stateNegative feedback mechanism Negative feedback mechanism

A series of changes that return the controlled A series of changes that return the controlled variable toward a variable toward a certain mean value, thus certain mean value, thus maintaining homeostasismaintaining homeostasis

Most control systems of the body act by a Most control systems of the body act by a process of negative process of negative feedback feedback

Negative-feedback system Negative-feedback system An increase or decrease in the variable being regulated An increase or decrease in the variable being regulated

brings about responses that brings about responses that tend to move the variable in tend to move the variable in the direction opposite (“negative” to) the direction of the direction opposite (“negative” to) the direction of the original change.the original change. The response returns the controlled The response returns the controlled variable back to its normal value, variable back to its normal value, the response is the response is ‘against’ the change‘against’ the change• the the decrease decrease in body temperature leads to responses in body temperature leads to responses

that tend to that tend to increase increase the body temperature – that is, the body temperature – that is, move it toward its original value.move it toward its original value.

• the the increase increase in ECF concentration of C02 in ECF concentration of C02 (initiating (initiating stimulus) stimulus) leads to responses that tend toleads to responses that tend to increase increase pulmonary ventilation pulmonary ventilation lungs expire greater lungs expire greater amounts of CO2 from the body amounts of CO2 from the body decreases back ECF decreases back ECF [C02] ([C02] (negative response to the initiating stimulus)negative response to the initiating stimulus)

Elaine N. Marieb, Katja Hoehn: Human Anatomy & Elaine N. Marieb, Katja Hoehn: Human Anatomy & Physiology 7Physiology 7thth ed, 2006 ed, 2006

Elaine N. Marieb, Katja Hoehn: Human Elaine N. Marieb, Katja Hoehn: Human Anatomy & Physiology 7Anatomy & Physiology 7thth ed, 2006 ed, 2006

Vander et al.: Human Physiology: The Vander et al.: Human Physiology: The

Mechanism of Body Function, Eighth Edition, © Mechanism of Body Function, Eighth Edition, © The McGraw−HillThe McGraw−HillCompanies, 2001Companies, 2001

Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition, Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition,

© The McGraw−Hill© The McGraw−HillCompanies, 2001Companies, 2001

The homeostatic control system maintains a The homeostatic control system maintains a relatively constant body temperature when relatively constant body temperature when room temperature decreases. room temperature decreases. The “begin” sign indicates where to start. The “begin” sign indicates where to start. The arrows next to each term within the The arrows next to each term within the boxes denote increases or decreases. boxes denote increases or decreases. The arrows connecting any two boxes in the The arrows connecting any two boxes in the figure denote cause and effect; that is, an figure denote cause and effect; that is, an arrow can be read as “causes” or “leads to.” arrow can be read as “causes” or “leads to.” In general, one should add the words “tends In general, one should add the words “tends to” in thinking about these causeand-effect to” in thinking about these causeand-effect relationships. For example, decreased room relationships. For example, decreased room temperature tends to cause an increase in temperature tends to cause an increase in heat loss from the body, and curling up heat loss from the body, and curling up tends to cause a decrease in heat loss from tends to cause a decrease in heat loss from the body. the body. Qualifying the relationship in this way is Qualifying the relationship in this way is necessary because variables like heat necessary because variables like heat production and heat loss are under the production and heat loss are under the influence of many factors, some of which influence of many factors, some of which oppose each other.oppose each other.

Vander et al.: Human Physiology: The Mechanism of Body Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition, © The McGraw−HillFunction, Eighth Edition, © The McGraw−Hill


Vander et al.: Human Physiology: The Mechanism Vander et al.: Human Physiology: The Mechanism

of Body Function, Eighth Edition, © The of Body Function, Eighth Edition, © The McGraw−HillMcGraw−Hill


Ganong’s Review of Medical Ganong’s Review of Medical Physiology 23Physiology 23rdrd ed, 2009 ed, 2009

Characteristics of Control System – Characteristics of Control System – Feedback mechanisms Feedback mechanisms

Positive Feedback: Positive Feedback: •An initial disturbance in a system sets off a train of events An initial disturbance in a system sets off a train of events

that increase the disturbance even further. that increase the disturbance even further. •Positive feedback does not favor stability and often Positive feedback does not favor stability and often

abruptly displaces a system away from its normal set abruptly displaces a system away from its normal set point.point.

•The greater the initiating stimulus, the more the The greater the initiating stimulus, the more the controlling system is activated.controlling system is activated.

•Does not happen very often in biological system, does not Does not happen very often in biological system, does not lead to stability, but to instability and often to death.lead to stability, but to instability and often to death.

•Known as Known as “vicious circle” “vicious circle” •A mild degree of positive feedback can be overcome by A mild degree of positive feedback can be overcome by

negative feedback control negative feedback control vicious circle vicious circle fails to developfails to develop• In certain circumstances, positive feedback occurs to be In certain circumstances, positive feedback occurs to be

useful useful ChildbirthChildbirth

Descending of the baby Descending of the baby cervix stretched cervix stretched signals signals from the cervix from the cervix uterine contractions uterine contractions more more stretched cervix stretched cervix more intense signals more intense signals more more powerful uterine contractions powerful uterine contractions birth of the baby birth of the baby

Characteristics of Control System – Characteristics of Control System – Feedback mechanismsFeedback mechanisms

Positive Feedback:Positive Feedback:

Estrogens Estrogens Increased Increased oxytocinoxytocin receptors receptors Uterine distention Uterine distention ProstaglandinProstaglandin

Uterine contractionsUterine contractions

Dilatation of cervix and distention of vaginaDilatation of cervix and distention of vagina

Stimuli from cervix and vaginaStimuli from cervix and vagina

Increased secretion of oxytocinIncreased secretion of oxytocin

Vicious cycle Vicious cycle If one or more functional systems lose their ability to function properly If one or more functional systems lose their ability to function properly

the optimal condition of the internal environment can not be maintained the optimal condition of the internal environment can not be maintained

drives the body away from normal homeostasis drives the body away from normal homeostasis

vicious cyclevicious cycle

homeostatic failure homeostatic failure

cells of the body suffer cells of the body suffer

pathophysiologic condition pathophysiologic condition

may lead to death. may lead to death.

Vander et al.: Human Physiology: The Mechanism of Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition, © The McGraw−HillBody Function, Eighth Edition, © The McGraw−Hill


Adaptation Adaptation • Living systems are constantly adjusting and reacting Living systems are constantly adjusting and reacting

(”responses”) (”responses”) to changes to changes (”stimuli” ) (”stimuli” ) in the environmentin the environment• Immediate response:Immediate response:

Painful stimulus Painful stimulus increased blood pressure increased blood pressure Exercise Exercise increased blood pressure increased blood pressure immediate immediate

adaptation to supply the exercising muscles (’ the new adaptation to supply the exercising muscles (’ the new circumstances’) with blood, limited by muscle soreness and circumstances’) with blood, limited by muscle soreness and fatiguefatigue

• Response to long-lasting environment changesResponse to long-lasting environment changes Basic biochemistry changes in ‘trained muscles’:Basic biochemistry changes in ‘trained muscles’:

o Increased number of open capillaries supplying the Increased number of open capillaries supplying the musclemuscle

o Increased blood supply, contractile proteins, and Increased blood supply, contractile proteins, and oxygen-storing protein (myoglobin)oxygen-storing protein (myoglobin)

Adaptation to the new environment, muscle hypertrophy, Adaptation to the new environment, muscle hypertrophy, increase in size of the individual muscle cellsincrease in size of the individual muscle cells

Patient’s clinical condition

Clinical signs & symptoms

History & prognosis of the disease

Histopathological changes

(Pathology Anatomy)

(Clinical Pathology)

Abnormal function

(Pathophysiology) PathogenesisPathogenesis

Feedback mechanism failure

Trauma, stimuli

Normal Structure

(Anatomy, Histology)

Normal Function Trauma, stimuli

Feedback mechanism

Short Term Adaptation

Long Term Adaptation

Homeostasis

Physiology Biochemistry

Thank youThank you

pengantar homeostasis

Documents