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Introduction to Human Physiology Abdul Aleem Khan 1.

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Presentation on theme: "Introduction to Human Physiology Abdul Aleem Khan 1."— Presentation transcript:

1 Introduction to Human Physiology Abdul Aleem Khan 1

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3 WHAT IT “IS” HOW IT “WORKS” 3

4 A branch of science that deals with the functioning of Human body  How does the heart beat ?  How do we breathe ?  How do we see ?  How do we remember ?  How do we move ?  How do we reproduce? 4

5  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 organism  All most all life processes are governed by laws of physics and chemistry 5

6 Integumentary Physiology (system) Cardiovascular Physiology (system) Respiratory Physiology (system) Gastrointestinal Physiology (system) Renal Physiology (system) Reproductive Physiology (system) Musculo-skeletal Physiology (system) Neurophysiology Nervous system Endocrine Physiology (system) Immune Physiology (system) 6

7 Atoms Molecules Organelles Cells Tissues Organs SystemsOrganism 7

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10  The cell is the basic structural and functional unit of living organisms  The activity of an organism depends on both the individual and collective activity of its cells  The 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) 10

11  There 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 cells Three different types of muscle cells Fat Storage cells Nerve cells that transmit electrical impulses Cells for reproduction 11

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13 “La fixité du milieu intérieur est la condition de la vie libre.” “The fixity of the internal environment is the condition for free life.” 13

14 Claude Bernard in 1829 said: The proper functioning of the cells depends on precise regulation of the composition of their surrounding fluid. Surrounding fluid = Internal environment = Le Milieu interier 14

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16 Water is main solvent in living cells Hydrophilic molecules dissolve in water Hydrophobic molecules do not dissolve in water Amphiphilic - molecule part hydrophilic/part hydrophobic Intracellular fluid (inside cells) Body Water Plasma (inside blood vessels) Interstitial Fluid (outside blood vessels) Extracellular fluid (outside cells) 16

17 Major Elements% body wt Oxygen 65% Carbon 18% Hydrogen 10% Nitrogen 3.4% Mineral Elements Sodium 0.17% Potassium 0.28% Chloride 0.16% Calcium 1.5% Magnesium 0.05% Phosphorus 1.2% Sulphur 0.25% Trace Elements Iron 0.007% Zinc 0.002% Principal organic constituents carbohydrates  sugars fats  fatty acids proteins  amino acids nucleic acids  nuclotides Water = 60% adult male = 50% adult female 17

18  Nutrients and oxygen are distributed by the blood  Metabolic wastes are eliminated by the urinary and respiratory systems 18

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20 Walter Cannon (1929) Maintenance of constancy of the Internal Environment 20

21 Open Loop Systems Closed Loop Systems (Feedback Systems) Control center (Set point) Effector Controlled variable Sensor Control center Effector Controlled variable Feedback Systems are of two types: 1. Negative feedback 2.Positive feedback 21

22 Maintenance of constancy of the Internal Environment 22

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24 Process 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 composition Organismal homeostasis - extracellular fluid composition. Control system designed to maintain level of given variable (concentration, temperature, pressure) within defined range following disturbance. 24

25 Negative feedback loop requires : specific to variable needing to be controlled Sensor (Detecto r) : specific to variable needing to be controlled reference point for sensor to compare against Comparator ( Control system): reference point for sensor to compare against if sensor  comparator  Error Signal  restore variable to desired level Effector: if sensor  comparator  Error Signal  restore variable to desired level Comparator (reference point) Effector Controlled variable SensorDisturbanceErrorsignal 25

26  Homeostatic range -oscillation around setpoint  Change in setpoint 1.Acclimatization 2.Biorhythms 26

27 The response reverses the original stimulus. Example:Blood pressure and blood glucose regulation The response enhances the original stimulus Example child birth 27

28 Composed of 1.Detector 2.Control system 3.Effector The effector response Decreases or increases the effect of the original stimulus 28

29 Stimulus: change in BP Receptors: Baroreceptors Control Center: Brain Effector: Heart 29

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33 Negative feedback control is initiated after variable is disturbed Negative feedback control is initiated after variable is disturbed Amount of correction to be applied, is assessed by magnitude of error signal  incomplete correction Amount of correction to be applied, is assessed by magnitude of error signal  incomplete correction Overcorrection  oscillations in controlled variable Overcorrection  oscillations in controlled variable Disadvantages overcome by multiple regulatory mechanisms. Disadvantages overcome by multiple regulatory mechanisms. Regulation of blood [glucose] Insulin   [glucose] blood Glucagon   [glucose] blood 33

34 Negative feedback - error signal  reduces deviation from reference point Negative feedback - error signal  reduces deviation from reference point Positive feedback - error signal  increases deviation from reference point (vicious circle) Positive feedback - error signal  increases deviation from reference point (vicious circle) controlledvariabledisturbanceeffector sensor + + Error signal 34

35 Stimulus: stretch of the uterus Receptors: stretch receptors (cervix) Control Center: Brain Effector: Uterus 35

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37  Homeostasis 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. 37


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