Electrolytes

Fluid makes up about - % of our weight on average. Skeletal muscle is - %, and adipose is - %

65,70,20

Intracellular fluid (ICF)

Fluid WITHIN the cells

-Enclosed by plasma membrane

-2/3 of total fluid volume

Extracellular fluid (ECF)

Fluid OUTSIDE of cells

-Interstitial fluid that “bathes the cell”, like CSF, synovial fluid, and pleural fluid

What is in ICF?

Proteins

-K+, Mg+, PO4 3-

Within the ECF, the composition is - interstitial fluid and - blood plasma

2/3, 1/3 of total extracellular fluid volume.

What is in ECF?

Electrolytes / little to no protein

-Na+, Ca2+, Cl-, HCO3-

Osmolarity

Measurement of the solute concentration of a solution

-When balance between compartments is “off”, water moves by osmosis to restore concentration equally

-THINK OF A BALANCE SCALE

Fluid intake

Water from food and drink (2.3 liters)

Hypertonic

Increased sodium or decreased water in ECF

-Will cause movement of water into ECF

Hypotonic

Increased water or decreased sodium in the ECF

-Will cause movement of water out of ECF

Sensible water loss

Measurable water loss

-Urine and feces

Insensible water loss

Immeasurable water loss

-Sweat / cutaneous transpiration

-Respiration

Obligatory water loss

Always occurs regardless of hydration state (urine, sweat)

Facultative water loss

Controlled water loss (content of urine that’s controlled by kidneys)

Electrolytes

Substance that dissolves in water to form cations and anions

-Conduct electrical current

-Exert more osmotic pressure then no electrolytes

Nonelectrolytes

Do not dissociate in water

-Glucose, urea, creatine

Fixed acid

”Metabolic acid”

-Produced from metabolic wastes, like lactic acidP

Physiologic buffering system for fixed acid

Regulated by kidney through resorption of HCO3- and elimination of H+

Volatile acid

Produced when carbon dioxide and water combine

-Carbonic acid H2CO3

Physiological buffering system for volatile acid

Regulated by respiratory rate

Normal pH of blood is from

7.35-7.45

Acidosis

blood pH lower than 7.35, is too acidic

Alkalosis

blood pH higher than 7.45, is too basic

For small changes, our buffering systems can return blood to normal pH. This is known as -

Compensation

When systems fail to return blood pH to normal, this becomes an acid-base disturbance, which is known as as -

Uncompensated

Respiratory acidosis

PCO2 (partial pressure of carbon dioxide) in arterial blood is above 45 mmHg

-Hypoventilation

-Occurs due to respiratory center dysfunction, loss of muscle respiration, airway obstruction, of difficulty with gas exchange because of alveolar membrane disease

Respiratory alkalosis

PCO2 in arterial blood is below 35mmHg

-Hyperventilation=more O2, less CO2

-Anxiety, increased altitude, pulmonary embolism

Metabolic acidosis

Decrease in blood plasma HCO3-. Below 22mEq/L

-Accumulated too much acid, OR lost too much bicarbonate

-Ketoacidosis in diabetes, lactic acid production from anaerobic respiration, acetic acid from too much alcohol

-Retention in kidney failure

-Loss of bicarbonate-diarrhea

Metabolic alkalosis

Increase in blood plasma HCO3- over 26 mEq/L

-Vomiting is the most common cause

-LOSS OF HCL

-Increase loss by kidneys

-Diuretics overuse

-Increase in antacid use

Renal: slow response: DECREASE in pH

Compensation method by the body

-Increased hydrogen ions in blood

-Reabsorption of bicarbonate from urine

-Secrete more H+

Renal: slow response: increase in pH

Compensation method by the body

-Decreased hydrogen ions in blood

-Decrease of reabsorption of HCO3-

-Decrease secretion of H+

Respiratory response: metabolic acidosis

Increase in respiratory rate or more oxygen

Respiratory response: metabolic alkalosis

Decrease in respiratory rate in response to more CO2

Respiratory compensation is - - - as renal compensation

Not as effective

Fluid imbalance

When output doesn’t equal input of fluid

5 categories: volume depletion, volume excess, dehydration, hypotonic hydration, fluid sequestration

Constant osmolarity

Volume of the fluid changes, but not the concentration of solutes (osmolarity)

Ex: you’re losing or gaining water through bleeding, sweating, vomiting, yet the ratio of solutes to water in the body remains the same, so no shifts in compartments occur

Dehydration

Loss of water through different methods (sweat hyposecretion of ADH, etc.)

-Water loss is greater than soluble loss, hypertonic, causing water to shift from interstitial space to the blood

Hypotonic hydration

“Water intoxication”

-Too much water from drinking large amounts of water, hyper secretion of ADH-hypotonic

-As a result, fluid will move from blood to tissues

Fluid sequestration

Total body fluid normal, but distributed abnormally

-Example: edema

Fluid balance is regulated -

Indirectly

-By monitoring blood volume, blood pressure, blood plasma, and osmolarity

Thirst center-turn on

Regulated by the ANS in the hypothalamus

-When water absorption IS needed

-Examples may be decreased salivary gland secretions, increased blood osmolarity, and decrease in blood pressure

-THIS WILL RESULT IN RENIN BEING RELEASED

Thirst center-turn off

Regulated by the ANS in the hypothalamus

-When water absorption ISN’T needed

-Examples may be increased salivary secretions, distention of the stomach, decreased blood osmolarity, and increase in blood pressure due to increased in BV

-INHIBIT RENIN RELEASE

Sodium overview

Most important electrolyte in regulating fluid balance:regulates flow of water

-“Water follows sodium” to balance the concentration

-Will cause ECF to be hyper/hypo-tonic

-99% in ECF

Potassium overview

Cell function, electrical activity, and fluid balance

-May cause cardiac arrest/heart problems if not regulated

-98% is in the ICF

Potassium and hydrogen ions

When H+ (acid) increases in the blood (ECF), it enters cells (ICF), making them too acidic. To restore balance, K+ (potassium) leaves the cells and enters ECF, swapping places with H+

-This corrects acid-base imbalance

Potassium and insulin

Insulin is released when blood sugar rises. Lowers both BS and K+ by activating pumps to move potassium INTO the cells. Helps to balance potassium levels after eating

Chloride overview

Works with sodium to balance fluids and control water distribution

-Acid-base balance

-Digestive function

-Nerve and muscle function

-Regulated the same way as sodium

Calcium overview

99% stored in bone and teeth

-Calcium phosphate make them “hard” , which is why it’s pumped into the sarcoplasmic reticulum

-Input from diet for healthy bones

Phosphate (PO4)3- overview

Most abundant anion in the ICF 85% forms teeth and bone

-With calcium as calcium phosphate

-Intake from diet

-Also important for energy production

Magnesium overview

Mainly in bone and ICF

-Enzyme activation

-Output through urine

Angiotensin II

Stimulates thirst center in hypothalamus-ultimate goal is maintenance of fluid, thus blood pressure

-Causes blood vessels to vasoconstriction, increasing BP

-Kidneys will decrease urine output by decreasing GFR

Antidiuretic hormone

Water retention, regulation of BP, concentration of urine

-Chemoreceptors in the hypothalamus monitor the increase in blood osmolarity, low blood pressure, and low blood volume

-Also knows as “Vasopressin”

Aldosterone overview

Hormone that regulates sodium and potassium levels

-Promotes sodium reabsorption in the kidneys, increasing water retention and BP

-Increases the number of Na+ / K + active and Na+ channels open

Atrial natriuretic peptide Overview

Helps lower blood volume and pressure by promoting sodium and water excretion

-Inhibits sodium retention

-COUNTER-REGULATOR TO SYSTEM THAT INCREASE BP (rein-angiotensin-aldosterone system)

Chemical buffering systems

Molecules which can bind to and release hydrogen ions to regulate

-Protein , Phosphate ((PO4)3-), and Bicarbonate (HCO3-)

-Each one dissociates to make either a base or an acid weaker