Fluids

Fluid outside cells

Extracellular fluid (ECF)

Cytosol (fluid inside cells)

Intracellular fluid

Most of our body is composed of this

Water

Balance between the amount of water gained and the amount of water lost

Involves regulating the content and distribution of body water in the ECF and the ICF

Fluid balance

Water gain in what 2 ways?

Water loss in what 2 ways?

Gain: Absorption by the digestive system + metabolic reactions

Lost: Excretion in urine and feces + perspiration and breathing

Balance between the amount of electrolytes gained and the amount of electrolytes lost

Electrolyte balance

Ions released through dissociation of inorganic compounds

Can conduct electrical current in solution

Electrolytes

Electrolytes gains (1)?

Electrolyte losses (2)?

Gains: Absorption by the digestive system

Losses: Excretion in urine and feces + perspiration

A balance between the amount of hydrogen ions (H+) gained and the amount of hydrogen ions (H+) lost

Acid-base balance

Water accounts for approximately what % of adult male body weight?

60%

Water accounts for what % of adult female body weight

50%

Intracellular fluid contains about what amount of total body water

2/3

What is the primary intracellular fluid?

Cytosol

What is the primary fluids of extracellular fluid?

What else?

Interstitial fluid of peripheral tissues and plasma of circulating blood

Lymph, cerebrospinal fluid, synovial fluid, serous fluids, aqueous humor of eye, perilymph and endolymph of the inner ear

More solutes in plasma than RBC and losing water is what kind of solution?

Dehydration

Hypertonic solutions

Water flows inside RBC to burst

More solutes inside RBC

Excessive fluids

Hypotonic solution

Same solute/water concentration as inside cells; water moves in + out

Isotonic solution

Solute exchnage between ICF and ECF occurs across selectively permeable plasma membranes by ________and______________(active and passive)

Diffusion + carrier-mediated transport

Solute exchanges between the subdivisions of ECF occur across the endothelial lining of capillaries and from interstitial spaces to plasma via _______________ that drain into the venous system

lymphatic vessels

Principal ions in the ICF (4)

Potassium

Magnesium

Phosphate ions

Negatively charged proteins

Principal ions of ECF (4)

Sodium

Chloride

Calcium

Bicarbonate

All homeostatic mechanisms that monitor and adjust body fluid composition respond to changes in the ______

ECF

Receptors monitor ______ and___________as indicators for fluid and electrolyte balance

Plasma volume and osmotic concentration

Cells cannot move water by active transport, only by ________

• "Water follows salt“

osmosis

Body’s water or electrolyte content will ____if gains exceed losses, and will _____if losses exceed gains

rise and fall

Released at the posterior pituitary gland when osmoreceptors of the hypothalamus detect higher osmotic concentration

Stimulates water conservation at the kidneys (late DCT & CD), reducing urinary water loss and concentrating urine (REABSORPTION)

Stimulates hypothalamic thirst center to promote fluid intake

Antidiuretic hormone (ADH)

Released by the adrenal glands in response to:

• increasing potassium/decreasing sodium

• in response to activating the RAAS

Stimulates sodium reabsorption and potassium loss (secretion) in the kidneys

Also stimulates water retention (water follows sodium)

Aldosterone

Released by cardiac muscle cells in response to abnormal stretching of the heart wall due to increased blood volume and blood pressure

Reduce thirst

Block the release of ADH and aldosterone

Stimulate diuresis (fluid loss by the kidneys) and therefore lower the blood pressure and plasma volume

Natriuretic peptides (ANP and BNP)

Under normal circumstances, is there significant water movement between ECF and ICF?

No

What % of ECF is in interstitial fluid and minor fluid compartments?

What % is in plasma?

80 and 20

Net hydrostatic pressure pushes water ____of plasma

Net colloid osmotic pressure draws water _____plasma

out

into

Movement of too much water from plasma into interstitial fluid

Caused by blockage of lymphatic drainage

Edema (tissue swelling)

Lymphedema

If water is lost (but electrolytes retained) what happens to osmotic concentration?

Osmotic concentration of ECF increases; becomes hypertonic compared to ICF

Water moves from ICF to ECF by osmosis

If water is gained (but electrolytes stay the same), what happens to the osmotic concentration?

The osmotic concentration of the ECF decreases; it becomes hypotonic compared to the ICF

Water moves from the ECF to the ICF (into cells) by osmosis

This happen when water losses are greater than gains

May results in excessive perspiration, inadequate water consumption, repeated vomiting, and diarrhea

Dehydration (water depletion)

Fluid shift causes water to move from where to where with dehydration?

ICF to ECF

What leads to a decrease in urination and increase in thirst?

Treatment?

ADH, aldosterone, and renin secretion

Increase drinking or IV fluids

What are 4 common IV fluids?

Normal saline

Lactated Ringer’s

Dextrose 5% in Water (DSW)

Half Normal Saline

Develops when water gains are greater than losses

May result from ingestion of a large volume of water, injection of hypotonic solution into bloodstream, inability to eliminate excess water in urine (chronic renal failure, heart failure, cirrhosis), excess ADH production

Hyperhydration (water excess)

What happens to ECF volume and osmotic concentration during hyperhydration?

Where does water move to and from?

ECF volume increases and ECF osmotic concentration decreases

Water moves from ECF to ICF

Response mechanisms in cases of severe water gain?

Treatment?

ADH decrease and ANP/BNP increase cause decrease in thirst and increase in water loss with urine

Administer diuretic drugs, IV of concentrated salt solution to promote fluid shift out of cells and treat the hyponatremia

4 IV Fluids for dehydration

Isotonic solutions (equal to blood serum)

Hypotonic solutions (lower concentration than blood)

Hypertonic solutions (higher concentration than blood)

Colloids (larger molecules)

When BV decreases due to sweating, from what source is water taken in by the blood?

Interstitial fluids (ECF)

What happens in tissues when capillary blood pressure is less than osmotic pressure?

Net reabsorption

Solute contributes to the movement of water between cells and the surrounding medium by?

Osmotic pressure

A cation has what charge?

Positive

Review Qs

Body generates acids during normal metabolism

Absorption by the digestive system

Hydrogen gains

Kidneys secrete H+ into urine and generate buffers that enter bloodstream

Lungs affect pH through elimination of CO2

Hydrogen loses

When gains and losses are equal for each electrolyte in the body

Electrolyte balance

Amount of positive or negative ion that supplies 1 mole of electrical charge

1 equivalent = 1000 milliequivalents (m E q)

Equivalent

Main cation in the ECF

Sodium chloride (NaCl) and sodium bicarbonate provide __% of ECF osmotic concentration

Sodium

90%

Are problems with potassium balance more or less common than sodium imbalance?

Less common, but more dangerous

Gains of this involve an uptake across digestive epithelium

Loss of this involve an excretion in urine and perspiration

If gains exceed losses, total content of ECF _________

Na+

increases

What is released when sodium gains exceed loses?

ADH, increasing thirst and water retention

If ECF volume rises, what else increases?

What is released?

Blood volume and blood pressure

Natriuretic peptides released

If ECF volume drops, what else decreases?

What is activated and what increases?

Blood volume and blood pressure decreases

The renin-angiotensin-aldosterone system is activated

Sympathetic stimulation increases

Na+ concentration of ECF < 135mEq/L

Caused by hyperhydration

---

Na+ concentration of ECF > 145mEg/L

Caused by dehydration

Hyponatremia

Hypernatremia

What percent of potassium in the body is in the ICF?

98%

Potassium gains include uptake across what?

Potassium loss in where?

digestive epithelium

Urine

Higher K+ concentration in ECF leads to higher rate of ______

Na+ exchanged for ___ rather than K+ so rate of K+ secretion declines

Increase in aldosterone leads to more ____ excretion in exchange for Na+

secretion

H+

K+

Low K+ in blood

Caused by certain diuretic drugs and excess aldosterone secretion

Results in muscle weakness and paralysis

Hypokalemia

Elevated level of K+ in blood

Caused by acidosis (low blood p H), kidney failure, and certain diuretic drugs

Results in over-excitable muscles and nerves, and cardiac arrhythmias

Hyperkalemia

This is the most abundant mineral in the body

98% is deposited in the skeleton

Calcium

Calcium is important for what 4 things?

For muscular and neural activities

For blood clotting

As cofactors for enzymatic reactions

As second messengers

Raise calcium concentrations in ECF

Decrease calcium concentrations in ECF

Parathyroid hormone (PTH) and calcitrol

Calcitonin

Ca+ gains result in absorption in ______

Reabsorption in ______

Stimulated by ____ and _____

---

Ca+ losses in _____, ____, or feces

usually small

digestive tract

kidneys

PTH and calcitriol

---

bile, urine

Ca+ concentration in ECF > 5.3 mEq/L

Caused by hyperparathyroidism (oversecretion of PTH), malignant cancers (breast, lung, kidney, and bone marrow) or excessive calcium or vitamin D supplementation

Results in fatigue, confusion, cardiac arrhythmias, calcifications in the kidneys and soft tissues

Hypercalcemia

Ca+ concentration in the ECF < 4.3 mEq/L

Caused by hypoparathyroidism (undersecretion of P T H), vitamin D deficiency, and chronic renal failure

Results in muscle spasms, convulsions, weak heart beats cardiac arrhythmias, and osteoporosis

Hypocalcemia

About ____% of magnesium deposited in skeleton

Where are magnesium ion primary found, the ECF or ICF?

Reabsorbed by what organ?

60%

ICF

Kidneys

A measure of the acidity or alkalinity of a solution

Depends on the amount of dissolved acids, bases, and salts

What is normal in the ECF/blood?

pH - 7.35-7.45

Abnormally low blood pH (pH<7.35)

Abnormally high blood pH (pH>7.45)

pH=7 is what?

Acidosis

Alkalosis

Neutral

Acid-base imbalance affect all body system but mostly which?

Is acidosis or alkalosis more common?

Nervous and cardiovascular systems

Acidosis

Acids that do not leave the solution (ex. sulfuric acid and phosphoric acid), eliminated through the kidneys

Acids (ex. pyruvic acid, lactic acid, ketone bodies) that can be metabolized without accumulation

Acids that leave the body by being breathed out by CO2 (*EQUATION*)

Fixed acids

Metabolic acids

Volatile acids

CO2 is converted to ________

carbonic acid

Carbonic acid dissociates into what 2 ions?

Hydrogen ions

Bicarbonate ions

Partial pressure of ___ is most important factor affecting blood pH

CO2

When CO2 levels increase, H+ and HCO3- increase and blood pH _____

*And vice versa

decreases

Hydrogen ions gained at ______

Lost at ______

neutralized by ______ to avoid tissue damage

digestive tract

kidneys and lungs

buffers

These dissociate completely in solution (ex. hydrochloric acid, HCl)

---

These do not dissociate complete in the solution, release fewer H+ (ex. carbonic acid

Strong acids and strong bases

Weak acids or weak bases

Dissolved compounds that stabilize the pH of a solution by adding or removing H+

Weak acids can donate H+ and weak bases can absorb H+

Buffers

Combination of weak acid and the anion released by its dissociation

Buffer systems

Most important buffer for the ICF and urine

Phosphate buffer system

_______ group of amino acid dissociates to release H+

________ groups and __ groups of amino acids can accept H+

Carboxyl

Amino, R

CO2 in RBCs converted to carbonic acid

Hemoglobin buffer system

Carbon dioxide is constantly generated by body cells and converted to carbonic acid

Most important buffer in ECF

Functions only when the respiratory system and the respiratory control centers are working normally

Carbonic acid-bicarbonate buffer system

Buffer system coordinate with these 2 mechanisms?

Respiratory and renal

Changing rate of ____ helps regulate CO2 levels and therefore pH

respiratory levels

Compensation for low pH (acidosis)

Decrease _____ by breathing faster

*Vice versa for alkalosis

PCO2

Buffers in urine are required to eliminate a lot or a little H+?

If pH of tubular fluid reaches 4-4.5, H+ _______ stops

a lot

secretion

Disturbance of acid-base balance from what conditions?

Disorders affecting circulating buffers, respiratory performance, or renal function, such as emphysema or renal failure

Cardiovascular conditions such as heart failure or hypotension

Conditions affecting the CNS, such as neural damage or disease, can disturb reflexes essential to p H regulation

Initial phase when pH moves rapidly out of the normal range

Physiological adjustments occur and return pH to the normal range, but compensatory mechanisms need to be active to keep it there

Acute phase

Compensated phase

Results from imbalance between CO2 generation in peripheral tissues and CO2 excretion at lungs. Cause abnormal CO2 levels in the ECF

Results form the generation of metabolic or fixed acids (increases H+ in ECF) or conditions affecting HCO3 concentration in the ECF

Respiratory acid-base disorders

Metabolic acid-base disorders

Low blood pH due to hypercapnia

Develops when respiratory system cannot elimination enough CO2

Primary cause is hypoventilation

Response:

• Respiratory compensation + renal compensation

Respiratory acidosis

Develops if decline in pH is severe and the lungs can not respond

Immediate, life-threatening condition

---

Develops when normal respiratory function has been compromised

Compensatory mechanisms have not failed completely

Examples: emphysema, congestive heart failure, pneumonia, and pneumothorax

Acute respiratory acidosis

Chronic respiratory acidosis

High blood pH due to hypocapnia (low blood PCO2)

Primary cause is hyperventilation (abnormally high respiratory rate)

• Examples: pain, stress, anxiety, high altitude, and patients on respirators

Responses:

• Respiratory compensation: decrease respiratory rate (ex. breathing into paper bag)

• Renal compensation: secrete bicarbonate ions and reabsorb hydrogen ions

Respiratory alkalosis

Major causes:

• High production of fixed or metabolic acids (H+ overload buffer system)

• Lactic acidosis after strenuous exercise or hypoxia

• Ketoacidosis due to starvation or diabetes mellitus

• Impaired H+ excretion at kidneys

• Severe bicarbonate ion loss (chronic diarrhea)

Responses:

• Respiratory compensation: increase respiratory rate

• Renal compensation: secrete hydrogen ions and reabsorb bicarbonate ions

Metabolic acidosis

Caused by elevated HCO3 concentrations and decreased H+ concentration

• Examples: alkaline tide after a meal and concentration

Responses:

• Respiratory compensation: decrease respiratory rate

• Renal compensation: secrete bicarbonate ions and reabsorb hydrogen ions

Metabolic alkalosis

These ions are required for bone mineralization

Found in ICF or ECF?

Reabsorbed where and lost where?

Phosphate

ICF

Kidneys, lost in urine and feces

The most abundant anion in the ECF

Absorbed in digestive tract and reabsorbed with what other ion

Chloride

Na+