NURS1004 Week 7 Lecture Fluid, Electrolyte Balance Lecture is in three parts.

Transcription

1 NURS1004 Week 7 Lecture Fluid, Electrolyte Balance Lecture is in three parts. Prepared by Didy Button

2 An Introduction to the Chemical Level of Organization Chemistry Is the science of change The structure of atoms The basic chemical building blocks How atoms combine to form increasingly complex structures

3 2-1 Atoms and Atomic Structure Matter Is made up of atoms Atoms join together to form chemicals with different characteristics Chemical characteristics determine physiology at the molecular and cellular levels

4 2-1 Atoms and Atomic Structure Subatomic Particles Proton Positive charge, 1 mass unit Neutron Neutral, 1 mass unit Electron Negative charge, low mass

5 2-1 Atoms and Atomic Structure Atomic Structure Atomic number Number of protons Nucleus Contains protons and neutrons Electron cloud Contains electrons

6 Figure 2-1 The Structure of Hydrogen Atoms Electron shell Hydrogen-1 mass number: 1 A typical hydrogen nucleus contains a proton and no neutrons. Hydrogen-2, Hydrogen-3, deuterium tritium mass number: 2 mass number: 3 A deuterium ( 2 H) nucleus contains a proton and a neutron. A tritium ( 3 H) nucleus contains a pair of neutrons in addition to the proton.

7 Table 2-1 Principal Elements in the Human Body

8 Table 2-1 Principal Elements in the Human Body

9 2-1 Atoms and Atomic Structure Elements and Isotopes Elements are determined by the atomic number of an atom Remember atomic number = number of protons Elements are the most basic chemicals

10 2-1 Atoms and Atomic Structure Elements and Isotopes Isotopes are the specific version of an element based on its mass number Mass number = number of protons plus the number of neutrons Only neutrons are different because the number of protons determines the element

11 2-1 Atoms and Atomic Structure Atomic Weights Exact mass of all particles Measured in moles Average of the mass numbers of the isotopes

12 2-1 Atoms and Atomic Structure Electrons and Energy Levels Electrons in the electron cloud determine the reactivity of an atom The electron cloud contains shells, or energy levels that hold a maximum number of electrons Lower shells fill first Outermost shell is the valence shell, and it determines bonding The number of electrons per shell corresponds to the number of atoms in that row of the periodic table

13 Figure 2-2 The Arrangement of Electrons into Energy Levels The first energy level can hold a maximum of two electrons. Hydrogen, H Atomic number: 1 Mass number: 1 1 electron Helium, He Atomic number: 2 Mass number: 4 (2 protons + 2 neutrons) 2 electrons

14 Figure 2-2 The Arrangement of Electrons into Energy Levels The second and third energy levels can each contain up to 8 electrons. Lithium, Li Atomic number: 3 Mass number: 6 (3 protons + 3 neutrons) 3 electrons Neon, Ne Atomic number: 10 Mass number: 20 (10 protons + 10 neutrons) 10 electrons

15 2-2 Molecules and Compounds Chemical Bonds Involve the sharing, gaining, and losing of electrons in the valence shell Three major types of chemical bonds 1. Ionic bonds Attraction between cations (electron donor) and anions (electron acceptor) 2. Covalent bonds Strong electron bonds involving shared electrons 3. Hydrogen bonds Weak polar bonds based on partial electrical attractions

16 2-2 Molecules and Compounds Chemical Bonds Form molecules and/or compounds Molecules Two or more atoms joined by strong bonds Compounds Two or more atoms OF DIFFERENT ELEMENTS joined by strong or weak bonds Compounds are all molecules, but not all molecules are compounds H 2 = molecule only H 2 O = molecule and compound

17 2-2 Molecules and Compounds Ionic Bonds One atom the electron donor loses one or more electrons and becomes a cation, with a positive charge Another atom the electron acceptor gains those same electrons and becomes an anion, with a negative charge Attraction between the opposite charges then draws the two ions together

18 Figure 2-3a The Formation of Ionic Bonds Formation of ions Sodium atom Attraction between opposite charges Sodium ion (Na + ) Formation of an ionic compound Chlorine atom Chloride ion (Cl ) Sodium chloride (NaCl) Formation of an ionic bond. 1 A sodium (Na) atom loses an electron, which is accepted by a chlorine (Cl) atom. 2 Because the sodium (Na + ) and chloride (Cl ) ions have opposite charges, they are attracted to one another. 3 The association of sodium and chloride ions forms the ionic compound sodium chloride.

19 Figure 2-3b The Formation of Ionic Bonds Chloride ions (Cl ) Sodium ions (Na + ) Sodium chloride crystal. Large numbers of sodium and chloride ions form a crystal of sodium chloride (table salt).

20 2-2 Molecules and Compounds Covalent Bonds Involve the sharing of pairs of electrons between atoms One electron is donated by each atom to make the pair of electrons Sharing one pair of electrons is a single covalent bond Sharing two pairs of electrons is a double covalent bond Sharing three pairs of electrons is a triple covalent bond

21 Figure 2-4 Covalent Bonds in Four Common Molecules Molecule Electron Shell Model and Structural Formula Hydrogen (H 2 ) H H Oxygen (O 2 ) O=O Carbon dioxide (CO 2 ) O=C=O Nitric oxide (NO) N=O

22 2-2 Molecules and Compounds Covalent Bonds Nonpolar covalent bonds Involve equal sharing of electrons because atoms involved in the bond have equal pull for the electrons Polar covalent bonds Involve the unequal sharing of electrons because one of the atoms involved in the bond has a disproportionately strong pull on the electrons Form polar molecules like water

23 Figure 2-5 Polar Covalent Bonds and the Structure of Water Hydrogen atom Hydrogen atom Oxygen atom Hydrogen atom δ + Oxygen atom δ + 2δ

24 2-2 Molecules and Compounds Hydrogen Bonds Bonds between adjacent molecules, not atoms Involve slightly positive and slightly negative portions of polar molecules being attracted to one another Hydrogen bonds between H 2 O molecules cause surface tension

25 Figure 2-6 Hydrogen Bonds between Water Molecules δ + δ + 2δ δ + 2δ δ + 2δ δ + δ + δ + 2δ δ + 2δ δ + 2δ δ + δ + 2δ KEY Hydrogen Oxygen Hydrogen bond

26 2-2 Molecules and Compounds Molecular Weights The molecular weight of a molecule is the sum of the atomic weights of its component atoms H = approximately 1 O = approximately 16 H 2 = approximately 2 H 2 O = approximately 18

27 2-2 Molecules and Compounds States of Matter Solid Constant volume and shape Liquid Gas Constant volume but changes shape Changes volume and shape END of Part I ( there are 3 Parts this week)

28 NURS1004 Week 7 Lecture Fluid, Electrolyte Balance Part II. Prepared by Didy Button

29 27-2 Fluid Compartments Fluid in the Body Water accounts for roughly: 60% of male body weight 50% of female body weight Mostly in intracellular fluid

30 2-6 Properties of Water Water Accounts for up to two-thirds of your total body weight A solution is a uniform mixture of two or more substances It consists of a solvent, or medium, in which atoms, ions, or molecules of another substance, called a solute, are individually dispersed

31 2-6 Properties of Water Solubility Water s ability to dissolve a solute in a solvent to make a solution Reactivity Most body chemistry occurs in water High Heat Capacity Water s ability to absorb and retain heat Lubrication To moisten and reduce friction

32 2-6 Properties of Water The Properties of Aqueous Solutions Ions and polar compounds undergo ionization, or dissociation in water Polar water molecules form hydration spheres around ions and small polar molecules to keep them in solution

33 Figure 2-9 The Activities of Water Molecules in Aqueous Solutions Hydration spheres Glucose molecule Negative pole Cl H Positive pole Na +

34 Figure 2-9a The Activities of Water Molecules in Aqueous Solutions Negative pole H Positive pole Water molecule. In a water molecule, oxygen forms polar covalent bonds with two hydrogen atoms. Because both hydrogen atoms are at one end of the molecule, it has an uneven distribution of charges, creating positive and negative poles.

35 Figure 2-9b The Activities of Water Molecules in Aqueous Solutions Cl Hydration spheres Na + Sodium chloride in solution. Ionic compounds, such as sodium chloride, dissociate in water as the polar water molecules break the ionic bonds in the large crystal structure. Each ion in solution is surrounded by water molecules, creating hydration spheres.

36 Figure 2-9c The Activities of Water Molecules in Aqueous Solutions Glucose molecule Glucose in solution. Hydration spheres also form around an organic molecule containing polar covalent bonds. If the molecule binds water strongly, as does glucose, it will be carried into solution in other words, it will dissolve. Note that the molecule does not dissociate, as occurs for ionic compounds.

37 Table 2-2 Important Electrolytes that Dissociate in Body Fluids

38 2-6 Properties of Water The Properties of Aqueous Solutions Electrolytes and body fluids Electrolytes are inorganic ions that conduct electricity in solution Electrolyte imbalance seriously disturbs vital body functions

39 2-6 Properties of Water The Properties of Aqueous Solutions Hydrophilic and hydrophobic compounds Hydrophilic hydro- = water, philos = loving Interacts with water Includes ions and polar molecules Hydrophobic phobos = fear Does NOT interact with water Includes nonpolar molecules, fats, and oils

40 2-6 Properties of Water Colloids and Suspensions Colloid A solution of very large organic molecules For example, blood plasma Suspension A solution in which particles settle (sediment) For example, whole blood Concentration The amount of solute in a solvent (mol/l, mg/ml)

41 Roles for water in the body: 1. Temperature control (perspiration). 2. Transport of nutrients & wastes (blood, interstitial fluid, urine, lymph, CSF). 3. Hydrolysis of food components in the gut during digestion, eg: C 12 H 22 O 11 + H 2 O C 6 H 12 O 6 + C 6 H 12 O 6 sucrose + water glucose + fructose 4. Maintain blood volume (& therefore BP)

42 Water intakes and losses Intake: Food consumed provides ~ 48% of our water Liquids drunk provide ~ 40% Produced by metabolism ~ 12% Losses: (catabolism of glucose, fatty acids & building proteins from amino acids) 43% in urine, 7% in faeces, 33% evaporated from skin 17% evaporated from lungs

43 27-2 Fluid Compartments Fluid in the Body Water accounts for roughly: 60% of male body weight 50% of female body weight Mostly in intracellular fluid

44 An Introduction to Fluid, Electrolyte, and Acid Base Balance Water Is 99% of fluid outside cells (extracellular fluid) Is an essential ingredient of cytosol (intracellular fluid) All cellular operations rely on water As a diffusion medium for gases, nutrients, and waste products

45 27-1 Fluid, Electrolyte, and Acid Base Balance The Body Must maintain normal volume and composition of: Extracellular fluid (ECF) Intracellular fluid (ICF)

46 Fluid compartments in the body Intra cellular fluid (ICF) Extra cellular fluid (ECF) The concentrations of solutes in the fluid within cells (ICF) is very different to the fluid that is outside cells (ECF) Electrolyte ICF (mmol/l) ECF (mmol/l) K Na SO 40 5 Cl Protein

47 Figure 27-3 Fluid Gains and Losses Water absorbed across digestive epithelium (2000 ml) Water vapor lost in respiration and evaporation from moist surfaces (1150 ml) ICF Metabolic water (300 ml) ECF Water lost in faeces (150 ml) Water secreted by sweat glands (variable) Plasma membranes Water lost in urine (1000 ml)

48 27-1 Fluid, Electrolyte, and Acid Base Balance Compartments % of body water ECF ICF Vascular 7 % Interstitial 18% ECF Connective tissue fluid 10 % Intra-cellular fluid (ICF) 63 % Trans-cellular 2%

49 27-2 Fluid Compartments Major Subdivisions of ECF Interstitial fluid of peripheral tissues Plasma of circulating blood Minor Subdivisions of ECF Lymph, perilymph, and endolymph Cerebrospinal fluid (CSF) Synovial fluid Serous fluids (pleural, pericardial, and peritoneal) Aqueous humor

50 27-1 Fluid, Electrolyte, and Acid Base Balance Fluid Balance Is a daily balance between: Amount of water gained Amount of water lost to environment Involves regulating content and distribution of body water in ECF and ICF The Digestive System Is the primary source of water gains Plus a small amount from metabolic activity The Urinary System Is the primary route of water loss

51 27-1 Fluid, Electrolyte, and Acid Base Balance Electrolyte Balance Electrolytes are ionic substances (Na+, K+, Ca2+, Mg2+, Cl-, HCO3 -) or substances which form ions when they dissolve. Electrolytes are ions released through dissociation of inorganic compounds Can conduct electrical current in solution Electrolyte balance When the gains and losses of all electrolytes are equal Primarily involves balancing rates of absorption across digestive tract with rates of loss at kidneys and sweat glands

52 27-2 Fluid Compartments Exchange among Subdivisions of ECF Occurs primarily across endothelial lining of capillaries From interstitial spaces to plasma Through lymphatic vessels that drain into the venous system

53 Figure 27-1a The Composition of the Human Body SOLID COMPONENTS (31.5 kg; 69.3 lbs) Kg Proteins Lipids Minerals Carbohydrates Miscellaneous The body composition (by weight, averaged for both sexes) and major body fluid compartments of a 70-kg individual.

54 Figure 27-1a The Composition of the Human Body WATER (38.5 kg; 84.7 lbs) Other Liters Plasma Interstitial fluid Intracellular fluid Extracellular fluid The body composition (by weight, averaged for both sexes) and major body fluid compartments of a 70-kg individual.

55 Figure 27-1b The Composition of the Human Body WATER 60% ICF Intracellular fluid 33% Interstitial fluid 21.5% ECF Plasma 4.5% Solids 40% (organic and inorganic materials) Other body fluids ( 1%) SOLIDS 40% Adult males A comparison of the body compositions of adult males and females, ages years.

56 Figure 27-1b The Composition of the Human Body WATER 50% ICF Intracellular fluid 27% Interstitial fluid 18% ECF Plasma 4.5% Solids 50% (organic and inorganic materials) Other body fluids ( 1%) SOLIDS 50% Adult females A comparison of the body compositions of adult males and females, ages years.

57 27-2 Fluid Compartments Membrane Functions Plasma membranes are selectively permeable Ions enter or leave via specific membrane channels Carrier mechanisms move specific ions in or out of cell

58 27-2 Fluid Compartments The Osmotic Concentration of ICF and ECF Is identical Osmosis eliminates minor differences in concentration Because plasma membranes are permeable to water

59 27-2 Fluid Compartments Basic Concepts in the Regulation of Fluids and Electrolytes 1. All homeostatic mechanisms that monitor and adjust body fluid composition respond to changes in the ECF, not in the ICF 2. No receptors directly monitor fluid or electrolyte balance 3. Cells cannot move water molecules by active transport 4. The body s water or electrolyte content will rise if dietary gains exceed environmental losses, and will fall if losses exceed gains END of Part II

60 NURS1004 Week 7 Lecture part III Prepared by Didy Button Berman et al Kozier & Erb s Fundamentals of Nursing 2 nd Australian ed. p 1624.

61 27-2 Fluid Compartments An Overview of the Primary Regulatory Hormones Affecting fluid and electrolyte balance 1. Antidiuretic hormone 2. Aldosterone 3. Natriuretic peptides

62 27-2 Fluid Compartments Antidiuretic Hormone (ADH) Stimulates water conservation at kidneys Reducing urinary water loss Concentrating urine Stimulates thirst center Promoting fluid intake

63 27-2 Fluid Compartments ADH Production Osmoreceptors in hypothalamus Monitor osmotic concentration of ECF Change in osmotic concentration Alters osmoreceptor activity Osmoreceptor neurons secrete ADH

64 27-2 Fluid Compartments ADH Release Axons of neurons in anterior hypothalamus Release ADH near fenestrated capillaries In neurohypophysis (posterior lobe of pituitary gland) Rate of release varies with osmotic concentration Higher osmotic concentration increases ADH release

65 27-3 Fluid Movement Movement of Water and Electrolytes When the body loses water: Plasma volume decreases Electrolyte concentrations rise When the body loses electrolytes: Water is lost by osmosis Regulatory mechanisms are different

66 Figure 27-3 Fluid Gains and Losses Water absorbed across digestive epithelium (2000 ml) Water vapor lost in respiration and evaporation from moist surfaces (1150 ml) ICF Metabolic water (300 ml) ECF Water lost in feces (150 ml) Water secreted by sweat glands (variable) Plasma membranes Water lost in urine (1000 ml)

67 Table 27-1 Water Balance

68 27-3 Fluid Movement Allocation of Water Losses Dehydration (Water Depletion) Develops when water loss is greater than gain If water is lost, but electrolytes retained: ECF osmotic concentration rises Water moves from ICF to ECF Net change in ECF is small

69 27-3 Fluid Movement Severe Water Loss Causes: Excessive perspiration Inadequate water consumption Repeated vomiting Diarrhea Homeostatic responses Physiologic mechanisms (ADH and renin secretion) Behavioral changes (increasing fluid intake)

70 Figure 27-4 Fluid Shifts between the ICF and ECF Intracellular fluid (ICF) Extracellular fluid (ECF) The ECF and ICF are in balance, with the two solutions isotonic. Decreased ECF volume Water loss from ECF reduces volume and makes this solution hypertonic with respect to the ICF. Decreased ICF volume Increased ECF volume An osmotic water shift from the ICF into the ECF restores osmotic equilibrium but reduces the ICF volume.

71 27-4 Electrolyte Balance Electrolyte Balance Requires rates of gain and loss of each electrolyte in the body to be equal Electrolyte concentration directly affects water balance Concentrations of individual electrolytes affect cell functions

72 27-4 Electrolyte Balance Sodium Is the dominant cation in ECF Sodium salts provide 90% of ECF osmotic concentration Sodium chloride (NaCl) Sodium bicarbonate (NaHCO 3 )

73 27-4 Electrolyte Balance Normal Sodium Concentrations In ECF About 140 meq/l In ICF Is 10 meq/l or less

74 27-4 Electrolyte Balance Potassium Is the dominant cation in ICF Normal potassium concentrations In ICF About 160 meq/l In ECF meq/l

75 27-4 Electrolyte Balance Rules of Electrolyte Balance 1. Most common problems with electrolyte balance are caused by imbalance between gains and losses of sodium ions 2. Problems with potassium balance are less common, but more dangerous than sodium imbalance

76 27-4 Electrolyte Balance Sodium Balance Total amount of sodium in ECF represents a balance between two factors 1. Sodium ion uptake across digestive epithelium 2. Sodium ion excretion in urine and perspiration

77 27-4 Electrolyte Balance Large Changes in ECF Volume Are corrected by homeostatic mechanisms that regulate blood volume and pressure If ECF volume rises, blood volume goes up If ECF volume drops, blood volume goes down

78 Figure 27-5 The Homeostatic Regulation of Normal Sodium Ion Concentrations in Body Fluids ADH Secretion Increases The secretion of ADH restricts water loss and stimulates thirst, promoting additional water consumption. Osmoreceptors in hypothalamus stimulated Recall of Fluids Because the ECF osmolarity increases, water shifts out of the ICF, increasing ECF volume and lowering Na + concentrations. HOMEOSTASIS DISTURBED Increased Na + levels in ECF HOMEOSTASIS RESTORED Decreased Na + levels in ECF HOMEOSTASIS Normal Na + concentration in ECF Start

79 Figure 27-5 The Homeostatic Regulation of Normal Sodium Ion Concentrations in Body Fluids HOMEOSTASIS DISTURBED Decreased Na + levels in ECF HOMEOSTASIS Normal Na + concentration in ECF Start HOMEOSTASIS RESTORED Increased Na + levels in ECF Osmoreceptors in hypothalamus inhibited ADH Secretion Decreases As soon as the osmotic concentration of the ECF drops by 2 percent or more, ADH secretion decreases, so thirst is suppressed and water losses at the kidneys increase. Water loss reduces ECF volume, concentrates ions

80 27-4 Electrolyte Balance Homeostatic Mechanisms A rise in blood volume elevates blood pressure A drop in blood volume lowers blood pressure Monitor ECF volume indirectly by monitoring blood pressure Baroreceptors at carotid sinus, aortic sinus, and right atrium

81 27-4 Electrolyte Balance Hyponatremia Body water content rises (overhydration) ECF Na + concentration <136 meq/l Hypernatremia Body water content declines (dehydration) ECF Na + concentration >145 meq/l

82 27-4 Electrolyte Balance Potassium Balance 98% of potassium in the human body is in ICF Cells expend energy to recover potassium ions diffused from cytoplasm into ECF Processes of Potassium Balance 1. Rate of gain across digestive epithelium 2. Rate of loss into urine

83 27-4 Electrolyte Balance Potassium Loss in Urine Is regulated by activities of ion pumps Along distal portions of nephron and collecting system Na + from tubular fluid is exchanged for K + in peritubular fluid Are limited to amount gained by absorption across digestive epithelium (about meq or g/day)

84 27-4 Electrolyte Balance Factors in Tubular Secretion of K + 1. Changes in K + concentration of ECF 2. Changes in ph 3. Aldosterone levels

85 27-4 Electrolyte Balance Changes in Concentration of K + in ECF Higher ECF concentration increases rate of secretion Changes in ph Low ECF ph lowers peritubular fluid ph H + rather than K + is exchanged for Na + in tubular fluid Rate of potassium secretion declines

86 27-4 Electrolyte Balance Aldosterone Levels Affect K + loss in urine Ion pumps reabsorb Na + from filtrate in exchange for K + from peritubular fluid High K + plasma concentrations stimulate aldosterone

87 27-7 Age and Fluid, Electrolyte Balance Aging and Fluid Balance Body water content, ages Males 55% Females 47% After age 60 Males 50% Females 45%

88 27-7 Age and Fluid, Electrolyte Balance Aging and Fluid Balance Decreased body water content reduces dilution of waste products, toxins, and drugs Reduction in glomerular filtration rate and number of functional nephrons Reduces ph regulation by renal compensation Ability to concentrate urine declines More water is lost in urine Insensible perspiration increases as skin becomes thinner

89 27-7 Age and Fluid, Electrolyte Balance Aging and Fluid Balance Maintaining fluid balance requires higher daily water intake Reduction in ADH and aldosterone sensitivity Reduces body water conservation when losses exceed gains Muscle mass and skeletal mass decrease Cause net loss in body mineral content Last Slide.