Download - Introduction to Physiology
Introduction to PhysiologyIntroduction to Physiology
PhysiologyPhysiology• Science of body functionsScience of body functions• Teleological vs Mechanistic viewsTeleological vs Mechanistic views
• Teleological – the why, explains purpose of a Teleological – the why, explains purpose of a physiological processphysiological process
• Mechanistic – the how, explained in terms of Mechanistic – the how, explained in terms of cause and effect of physiological processcause and effect of physiological process
• Example: shivering Example: shivering • Teleological - shivering elevates a low body Teleological - shivering elevates a low body
temperaturetemperature• Mechanistic - when body temperature drops below Mechanistic - when body temperature drops below
normal, a reflex pathway causes involuntary normal, a reflex pathway causes involuntary oscillating skeletal muscle contractions which oscillating skeletal muscle contractions which produce heatproduce heat
Levels of OrganizationLevels of Organization
• ChemicalChemical• CellularCellular• TissueTissue• OrgansOrgans• System LevelSystem Level• Organismic LevelOrganismic Level
Levels of Structural OrganizationLevels of Structural Organization• Chemical Level - atomic and molecular levelChemical Level - atomic and molecular level• Cellular level - smallest living unit of the bodyCellular level - smallest living unit of the body• Tissue levelTissue level
• Group of cells and the materials surrounding them Group of cells and the materials surrounding them that work together on one taskthat work together on one task
• 4 basic tissue types: epithelium, muscle, connective 4 basic tissue types: epithelium, muscle, connective tissue, and nervetissue, and nerve
• Organ level - consists of two or more types of primary tissues Organ level - consists of two or more types of primary tissues that function together to perform a particular function or that function together to perform a particular function or functionsfunctions
• Example: StomachExample: Stomach• Inside of stomach lined with epithelial tissueInside of stomach lined with epithelial tissue• Wall of stomach contains smooth muscleWall of stomach contains smooth muscle• Nervous tissue in stomach controls muscle contraction and gland secretionNervous tissue in stomach controls muscle contraction and gland secretion• Connective tissue binds all the above tissues togetherConnective tissue binds all the above tissues together
• System - collection of related organs with a common function, System - collection of related organs with a common function, sometimes an organ is part of more than one systemsometimes an organ is part of more than one system
• Organismic level - one living individualOrganismic level - one living individual
Levels of Structural OrganizationLevels of Structural Organization
Body SystemsBody Systems• Groups of organs that perform related Groups of organs that perform related
functions and interact to accomplish a functions and interact to accomplish a common activity essential to survival of the common activity essential to survival of the whole bodywhole body
• Do not act in isolation from one anotherDo not act in isolation from one another• Human body has 11 systemsHuman body has 11 systems
Body SystemsBody Systems
Body SystemsBody Systems
HomeostasisHomeostasis• Defined as maintenance of a relatively stable Defined as maintenance of a relatively stable
internal environmentinternal environment• Does not mean that composition, temperature, and Does not mean that composition, temperature, and
other characteristics are absolutely unchangingother characteristics are absolutely unchanging• Homeostasis is essential for survival and Homeostasis is essential for survival and
function of all cellsfunction of all cells• Each cell contributes to maintenance of a Each cell contributes to maintenance of a
relatively stable internal environmentrelatively stable internal environment
Basic Cell FunctionsBasic Cell Functions• Sensing and responding to changes in Sensing and responding to changes in
surrounding environmentsurrounding environment• Control exchange of materials between cell and Control exchange of materials between cell and
its surrounding environmentits surrounding environment• Obtain nutrients and oxygen from surrounding Obtain nutrients and oxygen from surrounding
environmentenvironment• Eliminate carbon dioxide and other wastes to Eliminate carbon dioxide and other wastes to
surrounding environmentsurrounding environment• Perform chemical reactions that provide energy Perform chemical reactions that provide energy
for the cellfor the cell• Synthesize needed cellular componentsSynthesize needed cellular components
HomeostasisHomeostasis• Body cells are in contained in Body cells are in contained in
watery internal environment watery internal environment through which life-sustaining through which life-sustaining exchanges are madeexchanges are made
• Extracellular fluid (ECF) - Fluid Extracellular fluid (ECF) - Fluid environment in which the cells environment in which the cells live (fluid outside the cells)live (fluid outside the cells)
• Two components: Two components: • PlasmaPlasma• Interstitial fluidInterstitial fluid
• Intracellular fluid (ICF) - Fluid Intracellular fluid (ICF) - Fluid contained within all body cellscontained within all body cells
HomeostasisHomeostasis
Cells, the fundamental units of life, exchange nutrients and wastes with their surroundings:
The intracellular fluid is “conditioned by”… the interstitial fluid, which is “conditioned by” … the plasma, which is “conditioned by” … the organ systems it passes through.
Balancing the Internal and External Environment
ICF ISF plasma organsexternal
environment internal environment
Homeostasis
• Homeostasis involves dynamic mechanisms that detect and respond to deviations in physiological variables from their “set point” values by initiating effector responses that restore the variables to the optimal physiological range.
• Two systems that maintain homeostasis are: Nervous system & Endocrine system
Maintenance of HomeostasisMaintenance of Homeostasis
• Nervous systemNervous system• Controls and coordinates bodily activities that require Controls and coordinates bodily activities that require
rapid responsesrapid responses• Detects and initiates reactions to changes in external Detects and initiates reactions to changes in external
environmentenvironment• Endocrine systemEndocrine system
• Secreting glands of endocrine regulate activities that Secreting glands of endocrine regulate activities that require duration rather than speedrequire duration rather than speed
• Controls concentration of nutrients and, by adjusting Controls concentration of nutrients and, by adjusting kidney function, controls internal environment’s volume kidney function, controls internal environment’s volume and electrolyte compositionand electrolyte composition
HomeostasisHomeostasisFactors homeostatically regulated includeFactors homeostatically regulated include• Concentration of nutrient moleculesConcentration of nutrient molecules• Concentration of water, salt, and other electrolytesConcentration of water, salt, and other electrolytes• Concentration of waste productsConcentration of waste products• Concentration of OConcentration of O2 2 = 100mmHg and CO = 100mmHg and CO2 2 = 40 mmHg= 40 mmHg• pH = 7.35pH = 7.35• Blood volume 4-6 L and pressure 120/80Blood volume 4-6 L and pressure 120/80• Temperature = 37Temperature = 37oo C C
Control of HomeostasisControl of Homeostasis
• Homeostasis is continually being Homeostasis is continually being disrupted bydisrupted by• External stimuli External stimuli
• heat, cold, lack of oxygen, heat, cold, lack of oxygen, pathogens, toxinspathogens, toxins
• Internal stimuliInternal stimuli• Body temperatureBody temperature• Blood pressureBlood pressure• Concentration of water, glucose, Concentration of water, glucose,
salts, oxygen, etc.salts, oxygen, etc.• Physical and psychological Physical and psychological
distressesdistresses• Disruptions can be mild to severeDisruptions can be mild to severe• If homeostasis is not maintained, If homeostasis is not maintained,
death may resultdeath may result
Control of HomeostasisControl of Homeostasis
Homeostatic Control SystemsHomeostatic Control Systems
• In order to maintain homeostasis, control In order to maintain homeostasis, control system must be able tosystem must be able to• Detect deviations from normal in the internal Detect deviations from normal in the internal
environment that need to be held within narrow environment that need to be held within narrow limitslimits
• Integrate this information with other relevant Integrate this information with other relevant informationinformation
• Make appropriate adjustments in order to restore Make appropriate adjustments in order to restore factor to its desired valuefactor to its desired value
Homeostatic Control SystemsHomeostatic Control Systems
• Control systems are grouped into two Control systems are grouped into two classesclasses• Intrinsic controlsIntrinsic controls
• Local controls that are inherent in an organLocal controls that are inherent in an organ• Extrinsic controlsExtrinsic controls
• Regulatory mechanisms initiated outside an organRegulatory mechanisms initiated outside an organ• Accomplished by nervous and endocrine systemsAccomplished by nervous and endocrine systems
Homeostatic Control SystemsHomeostatic Control Systems
• Feedforward - term used for responses Feedforward - term used for responses made in anticipation of a changemade in anticipation of a change
• Feedback - refers to responses made after Feedback - refers to responses made after change has been detectedchange has been detected• Types of feedback systemsTypes of feedback systems
• NegativeNegative• Positive Positive
Feedback Loops: TypesFeedback Loops: Types• Negative feedback loopNegative feedback loop
• original stimulus reversed original stimulus reversed • most feedback systems in the body are negativemost feedback systems in the body are negative• used for conditions that need frequent adjustmentused for conditions that need frequent adjustment
• Positive feedback loopPositive feedback loop• original stimulus intensifiedoriginal stimulus intensified• seen during normal childbirthseen during normal childbirth
Negative Feedback LoopNegative Feedback Loop• Negative feed back loop consists of:Negative feed back loop consists of:• Receptor - structures that monitor a controlled condition and detect Receptor - structures that monitor a controlled condition and detect
changeschanges
• Control center - determines next action Control center - determines next action
• EffectorEffector• receives directions from the control centerreceives directions from the control center• produces a response that restores the controlled conditionproduces a response that restores the controlled condition
Negative Feedback LoopNegative Feedback Loop
Negative Feedback LoopNegative Feedback Loop
Homeostasis – Negative Feedback LoopHomeostasis – Negative Feedback Loop• Blood glucose concentrations rise after a sugary meal (the Blood glucose concentrations rise after a sugary meal (the
stimulus), the hormone insulin is released and it speeds up the stimulus), the hormone insulin is released and it speeds up the transport of glucose out of the blood and into selected tissues (the transport of glucose out of the blood and into selected tissues (the response), so blood glucose concentrations decrease (thus response), so blood glucose concentrations decrease (thus decreasing the original stimulus). decreasing the original stimulus).
Homeostasis of Blood PressureHomeostasis of Blood Pressure• Baroreceptors in walls of Baroreceptors in walls of
blood vessels detect an blood vessels detect an increase in BPincrease in BP
• Brain receives input and Brain receives input and signals blood vessels and signals blood vessels and heartheart
• Blood vessels dilate, HR Blood vessels dilate, HR decreasesdecreases
• BP decreasesBP decreases
Positive Feedback during ChildbirthPositive Feedback during Childbirth• Stretch receptors in walls of uterus send signals to Stretch receptors in walls of uterus send signals to
the brainthe brain• Brain induces release of hormone (oxytocin) into Brain induces release of hormone (oxytocin) into
bloodstreambloodstream• Uterine smooth muscle contracts more forcefullyUterine smooth muscle contracts more forcefully• More stretch, more hormone, more contraction etc.More stretch, more hormone, more contraction etc.• Cycle ends with birth of the baby & decrease in Cycle ends with birth of the baby & decrease in
stretchstretch
Role of Body Systems in Role of Body Systems in HomeostasisHomeostasis