Haemostasis (1) (2) (1).pptx.......................................................

1. HOMOESTASIS & HOMEODYNAMISM 1

2. QUESTIONS Define the following; Intracellular homeostasis(1mk) Negative feedback system(1mk) Positive feedback system(1mk) 2. Differentiate between the following Extracellular and intracellular fluids(2mks) Sensible and insensible fluid loss(2mks) 3. State five ways how electrolytes are lost from the body (5mks) 4. List five areas where transcellular fluid can be found (2.5mks) 5. Explain the role of the following ions: Sodium ions (4mks) Bicarbonate ions(4mks) 2

3. Homeostasis From two greek words Homeo = similar Stasis = standing still Is the mechanism by which the body regulates and maintains a relatively constant steady and stable internal environment Ever changing external environment First conceived/postulated/suggested by claude bernard Coined/invented by walter B. cannon 3

4. External Environment External Environment External Environment External Environment Internal Environment Homeostasis is about staying the same ... but ... things don’t stay the same ... They CHANGE! Conditions change here constantly ... Where they cannot change is here ... The Internal Environment 4

5. Homeodynamism The internal environment is not in a true stable/static conditon There is oscillations from time to time Homeodynamism is the constantly changing interrelatedness of body components while an overall equilibrium is maintained 5

6. HOMEODYNAMISM One of the basic concepts of functional medicine in which the body maintains biochemical individuality by constantly undergoing physiologic and metabolic processes. The activities of cells, tissues, and organs must be regulated and integrated with each other in such a way that any change initiates a reaction to reestablish homeostasis. 6

7. Internal environment ECF contains ions and nutrients needed to maintain cell life All cells live in the same environment interstitial fluid (ISF) ECF = internal environment of the whole body 7

8. INTERNAL ENVIRONMENT Body water content is 45-75% of TBW( av 60%TBW) 2/3 (28L) of Body water is in the ICF compartment The balance (14L) is in the ECF compartment (Plasma plus ISF) In the ECF are the ions and nutrients needed by the cells to maintain cell life (Na+, Cl-,HCo3-, nutrients i.e. O2, Glucose, fatty/amino acids, Co2 plus other cellular waste products). Thus, all cells live in essentially the same environment (ECF). For this reason, the ECF is also called Internal Environment of the Body. ICF contains protein ions, K+, Phosphate ions and Mg2+ 8

9. Normalcy/normal range This is the narrow range for different parameters of the internal environment at which cellular process are able to function at a level consistent with continuation of life. Enzymes work well in certain conditions and may be denatured in extreme environment 9

10. Normal ranges 10

11. Distribution of water in the body 11

12. Cont.… Where do we obtain fluids from? Ingested fluids 1300 mol Water in foods 1000 mol Metabolism 300 mol Total 2600 mol How humans lose fluids Sensible fluid loss: refers to loss that is SEEN and Occurs through the skin Includes urine (1400mL), sweat (100mL), and faeces (100mL). Approximately 500 ml/day is lost through the skin. The kidneys excrete 800 to 1500 mol /day of fluid depending on the individual’s intake. 2. Insensible fluid loss: loss that is NOT SEEN. Occurs through the kidneys, intestinal tract, lungs, and skin. Includes water evaporation from the skin (350mL). Exhalation from the lungs accounts for approximately 350 mol /day fluid loss. Approximately 100 to 200 mol /day is lost through gastrointestinal output 12

13. Composition of body Fluids Body fluids contain many uncharged molecules (e.g. glucose and urea), but quantitatively speaking, electrolytes (ionized substances) contribute most to the total solute concentration (or osmolality) of body fluids 13

14. Electrolyte Composition of the Body Fluids Cation or Anion Plasma [Electrolyte] (mEq/L) Concentration in Plasma Water (mEq/kg H 2 O) [Interstitial Fluid] (mEq/kg H 2 O) [Intracellular Fluid] a (mEq/kg H 2 O) Cations Na + 142 153 145 10 K + 4 4.3 4 159 Ca 2+ 5 5.4 3 1 Mg 2+ 2 2.2 2 40 Total 153 164.9 154 210 Anions Cl - 103 111 117 3 HCO 3 - 25 27 28 7 Proteins 17 18 45 Others 8 9 9 155 Total 153 165 154 210 14

15. Measurement of fluid compartments This requires the use of an indicator substance, which is diffusion-restricted to a particular fluid compartment. Deuterium and tritiated water diffuse throughout the TBW; they can therefore be used to measure TBW. Inulin and mannitol are diffusion-restricted to the ECF compartment; they can therefore be used to measure ECF volume. Radiolabeled albumin ( 125 I-albumin) is diffusion restricted to the vascular compartment; it can therefore be used to measure plasma volume. 15

16. Vital Electrolytes within the body What are electrolytes? Electrolytes are elements that, when dissolved in water, acquire an electrical charge—positive or negative. Body fluid is mainly a mixture of water and electrolytes. 16

17. vital electrolytes: Sodium (Na + ) Potassium (K + ) Calcium (Ca 2+ ) Magnesium (Mg 2+ ) Chloride (Cl − ) Phosphate (HPO 4 2- ) Bicarbonate (HCO 3 - ) 17

18. Electrolytes can be found all over the body . 1. Potassium: found inside the cell; most plentiful electrolyte in the intracellular compartment. 2. Magnesium: found inside the cell; second most plentiful electrolyte in the body. 3. Sodium: Found outside the cell. Most plentiful electrolyte in the extracellular fluid. 4. Phosphorus: found inside the cell and in the bones. 5. Calcium: found mainly in bones and teeth; some floats around in the blood as well. 6. Chloride: found inside the cell, the blood, and the fluid between cells. 18

19. Properties of homeostasis Central concept of physiology Relatively stable internal environment Ever changing external environment Dynamic and steady Internal and external stress Failure = disease 19

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21. Control systems Must Detect deviation Intergrate information Make adjustments 21

22. CONTROL SYSTEMS Variable – is the factor or event being regulated. In control systems there are 3 interdependent components: 1. Receptor – type of sensor that monitors the environment and responds to changes, called stimuli, by sending information (input) to the second component (the control centre) 2. Control centre – determines the set point (level or range at which a variable is to be maintained), analyses the input it receives and then determines the appropriate response or course of action 22 1

23. 3. effector – provides the means for the control centre response (output) to the stimulus Examples of physiological variables Core temperature Water and electrolyte concentrations pH (acidity or alkalinity) of body fluids Blood glucose levels Blood and tissue oxygen and carbon dioxide levels Blood pressure 23

24. Cont. The whole body regulates its functions via 2 major systems; The nervous system Hormonal system 24

25. Regulations of the body functions 3 regulatory systems acts as one system “feedback control system” Autoregulation Direct and independent response Amplitude is smaller than the other two Less extensive 25

26. Nervous regulation Nerve reflex Autonomic nervous system Spatially determined information Nerve impulses Fast Localized Short lived Conditioned and unconditioned reflexes 26

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28. Endocrine system Hormones or active chemical substance Receptor distribution Slow Extensive Longer 28

29. FEEDBACK “Feedback,” a term borrowed from engineering. It can occur at multiple levels of organization, and it can be either negative or positive. It 'feeds back' the real value of the property to be regulated, compares it to the desired value and acts upon the deviation. 29

30. Feedback loops Sensor Integrating centre effector 30

31. NEGATIVE FEEDBACK A change in the variable being regulated brings about responses that tend to push the variable in the direction opposite to the original change. Minimizes changes from the set point of the system, leading to stability. The effector reverses the deviation from set point. May occur at the organ, cellular, or molecular level, and it is not unique to hormonal and neural pathways. 31

32. Negative feedback Activated to restore to original Small changes don’t become large Defends set point Main form of regulation Moves variable in the opposite 32

33. Negative feedback In systems controlled by negative feedback, the effector response decreases or negates the effect of the original stimulus, maintaining or restoring homeostasis (thus the term negative feedback 33

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36. Example of negative feed back 36

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39. Regulation of blood pressure Baroreceptors detect any resistance of blood flow against the vessel walls. These receptors relay a message to the medulla of the brain, which in turn sends a message to the effectors, the heart and blood vessels. 39

40. The heart rate falls and vasodilatation occurs, which causes the blood pressure to fall back within the normal range. Conversely, if blood pressure decreases, the receptors relay a message to the brain, which in turn causes the heart rate to increase, and the blood vessels to vasoconstriction. 40

41. Advantages Simplicity Generality Disadvantages Reactive rather than proactive Delayed response Incomplete compensation Overshoots the set point 41

42. POSITIVE FEEDBACK Positive feedback mechanisms are designed to accelerate or enhance ongoing output that has been activated by a stimulus. Unlike negative feedback, it can push levels beyond normal range and if unchecked, it can lead to a vicious cycle and dangerous situations. Thus, positive feedback mechanisms require an external brake to terminate them. 42

43. POSITIVE FEEDBACK The stimulus progressively increases the response, so that as long as the stimulus is continued the response is progressively amplified. The term positive refers to the response being in the same direction, leading to a cumulative or amplified effect. Examples include blood clotting and uterine contractions during labour. 43

44. Positive Feedback Mechanisms Characteristics : Time limitation – Processes in the body that must be completed within a constrained time frame are usually modified by positive feedback. Intensification of stress – During a positive feedback process, the initial imbalance or stress is intensified rather than reduced as it is in negative feedback. 44

45. Typical Positive Feedback Process 45

46. Positive feedback Increases and amplifies the action More instability Few types necessary for survival Short lived Less frequents events that do not require continuous adjustments Drives in the same direction Uncommon 46

47. Example 47

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50. FEED FORWARD Feed-forward control is an open-loop control in which a sequence of predefined actions is triggered by a certain stimulus. Feedforward regulation anticipates changes in a regulated variable, improves the speed of the body’s homeostatic responses, and minimizes fluctuations in the level of the variable being regulated, thereby reducing the amount of deviation from the setpoint . 50

51. Feedforward Concept: a direct effect of stimulus on the control system before the action of feedback signal occurs Prepare for change Less frequent Minimize lag time Disturb/interfere signal 51

52. Examples Pancreas releases insulin when food is ingested in anticipation of raise in blood sugar The stomach secrets gastric acid at the sight, smell or taste of food Gastrocolic reflex = food entering stomach promotes the motility of the colon, resulting in increased urge to defaecate . 52

53. Cont. Duodenocolic reflex = similar to above, encourages mass movements in colon - waves of prolonged contraction alongside relaxation of the haustra . Gastroileal reflex = peristaltic activity in the ileum is increased in response to a full stomach, so more chyme is forced through the iliocaecal sphincter 53

54. Advantages Fast Fore-see and adapt stable Prepare for change Disadvantages Complex Errors in response are not corrected 54

55. Adaptive control 55

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