Water, Electrolytes, Acid-Base Balance

Question 1

Fluid percentage

Answer 1

Human body is between 45% and 75% fluid

Question 2

What is fluid % based on?

Answer 2

Age
o Infants—highest percentage of fluid
o Elderly—lowest percentage
o Body fluid decreases with age
◦ Amounts of adipose and skeletal muscle tissue
o Adipose - 20% water
o Skeletal - 75% water

Question 3

Fluid in our body =

Answer 3

◦ intracellular + extracellular

Question 4

Intracellular fluid (ICF)

Answer 4

◦ Fluid within our cells
◦ Two-thirds of total body fluid
◦ Enclosed by plasma membrane
o Allows passage of some substances

Question 5

Extracellular fluid (ECF)

Answer 5

◦ Fluid outside our cells
consists of Interstitial fluid and blood plasma
Interstitial fluid and blood plasma similar
in composition

Question 6

Interstitial fluid

Answer 6

o Extracellular fluid surrounding cells
o Composes two-thirds of extracellular
fluid

Question 7

Blood plasma

Answer 7

o Extracellular fluid within blood vessels
o Separated from interstitial fluid by
capillary vessel wall

Question 8

Additional extracellular fluids:

Answer 8

◦ Cerebrospinal fluid
◦ Synovial joint fluid
◦ Aqueous and vitreous humor (eye)
◦ Fluids of inner ear
◦ Serous fluids
◦ Not typically subject to significant daily
gains and losses

Question 9

Intracellular and extracellular fluid are

Answer 9

chemically distinct
Due to transport proteins and intracellular processes

Question 10

Rule of thirds

Answer 10

2/3 Intracellular 1/3 Extracellular
2/3 Interstitial 1/3 Blood plasma

Question 11

Fluid movement between compartments

Answer 11

◦ Continuous in response to changes in osmolarity
◦ Concentration in compartment, hypotonic or hypertonic
o Continues until concentrations equal

Question 12

Where does Drinking water go

Answer 12

Water entering blood from digestive system > Decreases plasma osmolarity > water moves into interstitial fluid

Question 13

Fluid balance

Answer 13

◦ Fluid intake equal to fluid output
◦ Normal distribution of water and solutes in both compartments

Question 14

Fluid intake

Answer 14

◦ Addition of water to the body (2500 mL/day)

Question 15

Preformed water

Answer 15

(2300ml/day)
Water absorbed from food and drink

Question 16

Metabolic water

Answer 16

(200ml/day)
o Water produced from aerobic cellular respiration and dehydration synthesis

Question 17

Fluid output

Answer 17

◦ Loss of water from body (2500 mL/day)
o Breathing, sweating, defecation, evaporation of water through skin (40%)
o Urination (60%)
◦ Depends on physical activities, environment, and internal conditions

Question 18

Water loss can be:

Answer 18

◦ 1. Sensible
◦ Measurable, urine and feces
◦ 2. Insensible
◦ Not measurable, lost in expired air, sweat on skin
◦ 3. Obligatory
◦ Always occurs (breathing and through skin, amount necessary to eliminate urine in waste)
◦ 4. Facultative
◦ Controlled (dependent on hydration of body)
◦ Uses hormone systems

Question 19

Fluid imbalance and 5 types

Answer 19

– Occurs if fluid output does not equal fluid intake
– Organized into five categories
o Volume depletion
o Volume excess
o Dehydration
o Hypotonic hydration
o Fluid sequestration

Question 20

Fluid imbalance with constant osmolarity

Answer 20

depletion and excess

Question 21

Volume depletion

Answer 21

o Occurs when isotonic fluid loss is greater than isotonic fluid gain
o E.g., hemorrhage, severe burns, chronic vomiting, diarrhea

Question 22

Volume excess

Answer 22

o Isotonic fluid gain is greater than isotonic fluid loss
o Fluid intake normal but decreased fluid loss through kidneys

Question 23

in both excess and depletion

Answer 23

no change in osmolarity
◦ No net movement of water between compartments

Question 24

Fluid imbalance with changes in osmolarity

Answer 24

Dehydration and hypotonic hydration

Question 25

Dehydration

Answer 25

o Water loss greater than loss of solutes o Blood plasma becomes hypertonic o Water shifts from cells into interstitial fluid and blood plasma o Results from profuse sweating, diabetes, intake of alcohol, insufficient water intake, overexposure to cold weather

Question 26

Hypotonic hydration

Answer 26

water intoxication o Both Na+ and water lost during sweating ˗ Drinking water only replaces the water, not the solutes o Plasma becomes hypotonic o Fluid moving from blood plasma into interstitial fluid and into cells

Question 27

causers of hypotonic hydration and risk factors

Answer 27

* Possible swelling of cells / cerebral edema due to brain cells swelling * Convulsions, coma, and death in severe cases * Can result from ADH hypersecretion * More generally, from drinking large amount of plain water

Question 28

Fluid sequestration

Answer 28

◦ Body fluid distributed abnormally ◦ Edema, puffiness with fluid accumulation in interstitial space ◦ Other examples of fluid sequestration o Hemorrhage, ascites, pericardial effusion, pleural effusion

Question 29

Means of regulating fluid balance

Answer 29

– Monitor blood volume – Blood pressure – Blood plasma osmolarity * Relationship between these variables -Fluid intake < Fluid output: decrease BV and BP, possible increase in blood osmolarity -Fluid intake > fluid output: increase BV and BP, possible decrease in osmolarity

Question 30

what Regulates fluid intake

Answer 30

thirst center in hypothalamus

Question 31

thirst center activated by

Answer 31

1. . Decreased salivary secretions o Sensory input relayed from receptors in mucous membranes 2. Increased blood osmolarity o Due to insufficient water intake o Stimulates sensory receptors in thirst center directly o Stimulates hypothalamus to trigger release of ADH 3. Decreased blood pressure o Renin released from kidney o Initiates conversion of angiotensinogen to angiotensin II o Angiotensin II stimulates thirst center o Important with extreme volume depletion

Question 32

Thirst center inactivated by:

Answer 32

1. Increased salivary secretions o Decreased sensory input to thirst center 2. Distension of stomach o Stretch caused by fluid entering o Inhibitory sensory impulses relayed to thirst center 3. Decreased blood osmolarity o Thirst center is no longer stimulated directly o Decreased stimulation of ADH release 4. Increased blood pressure o Inhibits kidney from releasing renin o Decrease in angiotensin II results in reduced stimulation of thirst center

Question 33

Regulating fluid output via hormones

Answer 33

◦ Regulated through kidneys by controlling urine output o Angiotensin II, antidiuretic hormone (ADH), and aldosterone ˗ Decrease urine output o Atrial natriuretic peptide (ANP) ˗ Increases urine output Regulation of Fluid Balance

Question 34

Nonelectrolytes

Answer 34

◦ Molecules that do not dissociate in solution ◦ Covalently bonded organic molecules (ex. Glucose)

Question 35

Electrolytes

Answer 35

◦ Dissociate in solution to form cations and anions ◦ Ability of substances to conduct electrical current when dissolved ◦ Ex. Sodium, calcium, potassium

Question 36

Sodium ion (Na+)

Answer 36

◦ 99% in ECF and 1% in ICF ◦ Gradient maintained by Na+/K+ pumps ◦ Principle cation in ECF ◦ Exerts greatest osmotic pressure ◦ Influenced by diet, urine output, sweat, aldosterone, ADH and ANP ◦ ECF hypertonic if Na+ concentration increased ◦ Water moves from cells > plasma ◦ ECF hypotonic if Na+ concentration decreased ◦ Water moves from plasma > cells Major Electrolytes: Location, Functions, and Regulation ◦ Changes in plasma volume ◦ High sodium increases blood volume and pressure

Question 37

Sodium imbalance

Answer 37

◦ Most common electrolyte imbalance ◦ Hypernatremia – above normal level ◦ Hyponatremia – below normal level

Question 38

Potassium (K+)

Answer 38

◦ 98% in ICF, 2% in ECF ◦ Principle cation in ICF ◦ Exerts greatest intracellular osmotic pressure ◦ Influenced by diet, urine output, sweat, aldosterone, and pH ◦ Potassium distribution ◦ Based on Na/K pumps and leak channels

Question 39

Potassium balance

Answer 39

◦ Only the portion in the ECF is regulated ◦ Most lethal of electrolyte imbalances because of role in heart beat and neuromuscular communication

Question 40

Potassium shifts

Answer 40

Can redistribute in response to K, H and hormones

Question 41

Hyperkalemia

Answer 41

K moves from ECF > ICF in order to maintain normal

Question 42

Hypokalemia

Answer 42

K moves from ICF > ECF

Question 43

Chloride (Cl-)

Answer 43

◦ Follows Na by electrostatic interactions ◦ Amount lost in urine depends on blood plasma of Na ◦ Regulated by same mechanisms ◦ Most abundant anion in ECF ◦ Normal blood concentration: 96-106 mEq/L ◦ Obtained in diet / lost in sweat, stomach secretions, and urine

Question 44

Hypercholermia

Answer 44

– increased blood chloride

Question 45

Hypocholermia

Answer 45

– decreased blood chloride

Question 46

Calcium (Ca+)

Answer 46

◦ Most abundant electrolyte in bones and teeth ◦ 99% stored here ◦ Moved by pumps or cells into sarcoplasmic reticulum for storage ◦ Prevents binding to phosphate within cells and hardening ◦ Needed for muscle contraction / neurotransmitter release / second messenger cascades / blood clotting ◦ Obtained in diet / lost in urine, feces, and sweat ◦ Normal blood concentration: 5mEq/L

Question 47

Hypercalcemia

Answer 47

– increased blood calcium

Question 48

Hypocalcemia

Answer 48

– decreased blood calcium

Question 49

Phosphate (PO43-)

Answer 49

◦ Most abundant anion in ICF ◦ 85% stored in bone and teeth as calcium phosphate ◦ Component of DNA / RNA / phospholipids ◦ Most is ionized in blood plasma (90%) the rest is bound to proteins in the blood ◦ Normal blood concentration: 1.8-2.9 mEq/L ◦ Obtained in diet / lost in urine, feces, and sweat

Question 50

Hyperphosphatemia

Answer 50

– increased blood phosphate

Question 51

Hypophosphatemia

Answer 51

– decreased blood phosphate

Question 52

Magnesium (Mg2+)

Answer 52

◦ Primarily within bone or cells ◦ Second most abundant cation in ICF ◦ Participates in hundreds of enzymatic reactions ◦ Important in muscle relaxation ◦ Obtained in diet / lost in urine, feces, and sweat ◦ Normal blood concentration: 1.4-2.1 mEq/L

Question 53

Hypermagnesmia

Answer 53

– increased blood magnesium

Question 54

Hypomagnesmia

Answer 54

– decreased blood magnesium

Question 55

Acid-base balance

Answer 55

requires regulation of hydrogen ions (pH) ◦ Desired pH: 7.35-7.45 ◦ Regulated by: ◦ 1. Intake (diet) / output (intercalated cells in collecting tubule / duct) of acid / base 2. Respiratory rate ◦ When body is at rest, ◦ CO2 produced = CO2 eliminated ◦ When exercising ◦ CO2 produced > CO2 eliminated increased CO2 Levels detected by chemoreceptors = increased Breathing rate 3. Chemical buffering (ex. proteins) ◦ Temporary binding of a H+ until eliminated – limited in quantity

Question 56

Respiratory acid-base disturbances

Answer 56

occur when expiration of CO2 does NOT equal CO2 produced by cells

Question 57

Respiratory acidosis:

Answer 57

Decreased blood pH as a result of increased co2

Question 58

Respiratory alkalosis:

Answer 58

increased blood pH decreased co2

Question 59

Metabolic acidosis / alkalosis

Answer 59

-are also possible as a result of changes unrelated to respiratory function -Ex. vomiting, consuming large amounts of antacids, reduced stomach acid secretions