4What is human Physiology A branch of science that deals with the functioning of Human bodyHow does the heart beat ?How do we breathe ?How do we see ?How do we remember ?How do we move ?How do we reproduce?
5How cells (like muscle, nerve) function? To answer these global questions it is essential to understand that the functional unit of the body is the cell.How cells (like muscle, nerve) function?And how similar and dis-similar types of cells work together at various organisational levels (integration) as a whole organismAll most all life processes are governed by laws of physics and chemistry
10Cell theoryThe cell is the basic structural and functional unit of living organismsThe activity of an organism depends on both the individual and collective activity of its cellsThe biochemical activities of cells are dictated by their specific subcellular structures (principle of complementarity)Continuity of life has a cellular basis (cells come from cells)
11Cell DiversityThere is really no “typical” cell. Cells have different shapes, different sizes, different functions, different life spans.Stem cells is pluripotent.Examples of Specialized cells:Many different types of blood cellsThree different types of muscle cellsFat Storage cellsNerve cells that transmit electrical impulsesCells for reproduction
13“La fixité du milieu intérieur est la condition de la vie libre.” Claude Bernard( )“La fixité du milieu intérieur est la condition de la vie libre.”“The fixity of the internal environment is the condition for free life.”
14Internal EnvironmentClaude Bernard in 1829 said: The proper functioningof the cells depends on precise regulation ofthe composition of their surrounding fluid.Surrounding fluid = Internal environment= Le Milieu interier
16Body water Water is main solvent in living cells Hydrophilic molecules dissolve in waterHydrophobic molecules do not dissolve in waterAmphiphilic - molecule part hydrophilic/part hydrophobicBody WaterIntracellular fluid(inside cells)Extracellular fluid(outside cells)Plasma(insideblood vessels)Interstitial Fluid(outsideblood vessels)
17Chemical composition of body Major Elements % body wtOxygen %Carbon %Hydrogen %Nitrogen %Mineral ElementsSodium %Potassium %Chloride %Calcium %Magnesium %Phosphorus %Sulphur %Trace ElementsIron %Zinc %Water= 60% adult male= 50% adult femalePrincipal organic constituentscarbohydrates sugarsfats fatty acidsproteins amino acidsnucleic acids nuclotides
18Organ system Interrelationship Nutrients and oxygen are distributed by the bloodMetabolic wastes are eliminated by the urinary and respiratory systems
20Maintenance of constancy of the Internal Environment HomeostasisMaintenance of constancy of the Internal EnvironmentWalter Cannon(1929)
21Closed Loop Systems (Feedback Systems) Control SystemsOpen Loop SystemsControl centerEffectorControlledvariableClosed Loop Systems (Feedback Systems)Control center(Set point)EffectorControlledvariableSensorFeedback Systems are of two types: Negative feedback Positive feedback
22Maintenance of constancy of the Internal Environment HomeostasisMaintenance of constancy of the Internal Environment
23Physiological variables maintained by controlled systems
24HomeostasisProcess of maintaining the composition of the internal body compartments within fairly strict limits (ion concentrations, pH, osmolarity, temperature etc).Require regulatory mechanisms to defend against changes in external environment and changes due to activity.Cellular homeostasis - intracellular fluid compositionOrganismal homeostasis - extracellular fluid composition.Control system designed to maintain level of given variable (concentration, temperature, pressure) within defined range following disturbance.
25Negative feedback loop requires Sensor (Detector): specific to variable needing to be controlledComparator (Control system): reference point for sensor to compare againstEffector: if sensor comparator Error Signal restore variable to desired levelComparator(reference point)EffectorControlledvariableSensorDisturbanceErrorsignal
26Homeostasic Setpoint Homeostatic range -oscillation around setpoint Change in setpoint1. Acclimatization 2. Biorhythms
27Negative feedback System Negative feedback System The response reversesthe original stimulus.Example:Blood pressure andblood glucose regulationThe response enhancesthe original stimulusExample child birthNegative feedback System
28Maintenance of body temperature Composed ofDetectorControl systemEffectorThe effector responseDecreases or increasesthe effect of the originalstimulus
29Negative feedback System Receptors: Baroreceptors Stimulus: change in BPReceptors: BaroreceptorsControl Center: BrainEffector: Heart
33Limitation of negative feedback Negative feedback control is initiated after variable is disturbedAmount of correction to be applied, is assessed by magnitude of error signal incomplete correctionOvercorrection oscillations in controlled variableDisadvantages overcome by multiple regulatory mechanisms.Regulation of blood [glucose]Insulin [glucose]bloodGlucagon [glucose]blood
34Positive feedbackNegative feedback - error signal reduces deviation from reference pointPositive feedback - error signal increases deviation from reference point (vicious circle)Errorsignalcontrolledvariabledisturbanceeffectorsensor+
35Positive feedback System Stimulus: stretch of the uterusReceptors: stretch receptors (cervix)Control Center: BrainEffector: Uterus
37HomeostasisHomeostasis is the ability to maintain a relatively stable internal environment in an ever-changing outside world.The internal environment of the body is in a dynamic state of equilibrium.Concepts of homeostasis dynamic.Chemical, thermal, and neural factors interact to maintain homeostasis.