Chapter 7_1 flashcards

Question 1

Body Water Percentage & Primary Functions of Solutes

Answer 1

Human body is ~60% water. Electrolytes & protein (solutes) main functions: 1. Deliver nutrients/electrolytes to cells. 2. Carry away waste products from cellular metabolism.

Question 2

Three Main Fluid Compartments & Proportions

Answer 2

1. Intracellular Fluid (ICF): Inside cells (2/3 of body water, ~40% total body weight).
2. Extracellular Fluid (ECF): Within bloodstream (1/3 of body water, ~20% total body weight).
3. Interstitial Fluid (ISF): Between ICF and ECF (between cells and capillaries).

Question 3

Plasma Membrane Role in Fluid Exchange

Answer 3

Semipermeable; allows passive movement of fluid/electrolytes, restricts larger particles (like proteins).

Question 4

Transport Mechanism: Diffusion

Answer 4

Molecules passively spread from areas of high concentration to low concentration until equilibrium. Water and electrolytes use this.

Question 5

Transport Mechanism: Osmosis

Answer 5

Tendency of solvent molecules to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, equalizing concentrations. Water moves; large proteins (albumin) restricted.

Question 6

Transport Mechanism: Facilitated Transport & Example

Answer 6

Passing of certain molecules through plasma membrane with assistance from carrier proteins. Example: Glucose enters cell via insulin (carrier protein).

Question 7

Transport Mechanism: Active Transport & Example

Answer 7

Substance requires energy (ATP) to pass through a membrane against a concentration gradient. Example: Na+/K+ pump maintains K+ as major intracellular ion and Na+ as major extracellular ion.

Question 8

Intracellular Fluid (ICF) Compartment: Water Movement Consequences

Answer 8

Water diffusion out of ICF -> cell shrinkage/cellular dehydration. Water diffusion into ICF -> cell swelling/cellular edema.

Question 9

Extracellular Fluid (ECF) Compartment: Contents

Answer 9

Contains electrolytes, oxygen, glucose, other nutrients for cells, and cellular waste products for excretion.

Question 10

Interstitial Fluid (ISF) Compartment: Composition

Answer 10

A filtrate of blood, located between cells and capillaries. Contains water and electrolytes (mainly Na+). Lacks proteins (normally too large to diffuse out of capillaries).

Question 11

Hydrostatic Pressure: Definition & Source

Answer 11

The pushing force exerted by water in the bloodstream. Source: Heart’s pulsatile pumping action. Pushes water from ECF (capillaries) into ISF and ICF.

Question 12

Osmotic Pressure: Definition & Source

Answer 12

Pressure exerted by solutes in solution (mainly electrolytes like sodium, and plasma proteins). Pulls water into bloodstream from ICF and ISF; opposes hydrostatic pressure.

Question 13

Oncotic Pressure (Colloidal Osmotic Pressure): Definition & Key Protein

Answer 13

Type of osmotic pressure exerted specifically by albumin in bloodstream. Attracts water, keeps it inside blood vessels. Essential for maintaining this pressure.

Question 14

Normal Serum Albumin Level & Effect of Hypoalbuminemia

Answer 14

Normal: 3.1 to 4.3 g/dL. Hypoalbuminemia (low albumin) -> reduced oncotic pressure -> hydrostatic pressure overwhelms -> water pushed from ECF to ISF/ICF -> edema.

Question 15

Osmolality: Definition & Normal Plasma Value

Answer 15

Measurement of concentration of solutes per kg of solvent. Normal plasma osmolality: 282 to 295 mOsm/kg water. Low = dilute, High = concentrated.

Question 16

Osmolality: Clinical Use & Calculation Formula

Answer 16

Used to evaluate body’s hydration status. Formula: mOsm/kg = 2 × serum sodium (mEq/L) + serum glucose (mg/dL)/18 + BUN (mg/dL)/2.4.

Question 17

Osmolarity: Definition & Major Body Solutes

Answer 17

Number of osmoles of solute per liter of solution. Major solutes: Albumin, Sodium (Na+), Potassium (K+), Phosphate (PO4–), Magnesium (Mg++), Calcium (Ca++), Bicarbonate (HCO3–), Glucose. Na+ is main determinant.

Question 18

Tonicity: Definition

Answer 18

Concentration of solutes in a solution compared with the bloodstream.

Question 19

Isotonic IV Solution: Definition, Example & Purpose

Answer 19

Same tonicity as blood. Does not cause fluid shifts or alter cell size. Example: 0.9% NaCl (normal saline). Purpose: Bloodstream volume expander, keep IV route open.

Question 20

Hypotonic IV Solution: Definition, Example & Purpose

Answer 20

Fewer particles and more water than blood. Infusion adds water to bloodstream -> fluid shift from ECF to ICF (hydrates cells). Example: 0.45% NaCl (half normal saline). Purpose: Dehydration treatment.

Question 21

Hypertonic IV Solution: Definition, Example & Purpose

Answer 21

More particles and less water than blood. Infusion adds solutes to bloodstream -> fluid shift from ICF to ECF (shrinks cells). Example: Mannitol, 3.0% NaCl. Purpose: Diminish cell swelling (e.g., cerebral edema).

Question 22

Starling’s Law of Capillary Forces: Two Opposing Forces

Answer 22

At every capillary membrane: 1. Hydrostatic pressure (pushes fluid out of capillary). 2. Osmotic pressure (includes oncotic; pulls fluid into capillary). Normally balanced for homeostasis.

Question 23

Fluid Homeostasis: Key Regulatory Mechanisms

Answer 23

Kidney, Renin-Angiotensin-Aldosterone System (RAAS), Osmoreceptors, Thirst sensation, Antidiuretic Hormone (ADH), Natriuretic Peptides.

Question 24

Osmoreceptors, ADH, and Thirst Mechanism

Answer 24

High plasma osmolarity -> stimulates osmoreceptors in hypothalamus -> stimulates hypothalamic thirst center (conscious desire to drink) AND promotes ADH release from posterior pituitary. ADH -> water reabsorption by kidney.

Question 25

Antidiuretic Hormone (ADH) / Arginine Vasopressin: Action

Answer 25

Stimulates water reabsorption from nephron tubule fluid (at collecting duct) into bloodstream, raising blood’s water content and concentrating urine.

Question 26

Renin-Angiotensin-Aldosterone System (RAAS): Triggers

Answer 26

Hypotension, hypovolemia, dehydration, low cardiac output -> low renal perfusion -> kidney secretes renin.

Question 27

RAAS Pathway

Answer 27

Renin (kidney) -> Angiotensinogen (liver) to Angiotensin I -> ACE (lungs) converts Angiotensin I to Angiotensin II.

Question 28

Effects of Angiotensin II & Aldosterone (RAAS)

Answer 28

Angiotensin II: Potent vasoconstrictor; stimulates adrenal cortex to release Aldosterone. Aldosterone: Increases Na+ and water reabsorption into bloodstream at distal nephron tubule; stimulates K+ excretion into urine. Net effect: Raises blood volume and blood pressure.

Question 29

Natriuretic Peptides: Definition & Types

Answer 29

Peptides that promote natriuresis (excretion of large amount of Na+ and water by kidneys) in response to excess ECF volume. Types: Atrial Natriuretic Peptide (ANP), B-type Natriuretic Peptide (BNP), C-type Natriuretic Peptide (CNP).

Question 30

Source & Stimulus for ANP and BNP Release

Answer 30

ANP: Produced by heart’s atria; secreted in response to excess ECF volume stretching atria. BNP: Produced in heart’s ventricles (and brain); secreted in response to fluid volume overload stretching ventricles.

Question 31

Action of ANP and BNP

Answer 31

Promote natriuresis at the glomerulus by increasing glomerular filtration rate.

Question 32

Edema: Definition & General Causes

Answer 32

Excess fluid in ISF and ICF compartments. Causes: 1. Elevated hydrostatic pressure (excess water in bloodstream). 2. Diminished osmotic force (low solutes in bloodstream, e.g., hypoalbuminemia). 3. Inflammation (increased capillary permeability).

Question 33

Pulmonary Edema Example (Hydrostatic Pressure)

Answer 33

In left-sided heart failure, high hydrostatic pressure in pulmonary bloodstream forces fluid out of pulmonary vessels into alveolar spaces and interstitial tissue.

Question 34

Edema Example (Oncotic Pressure - Kwashiorkor)

Answer 34

Severe protein starvation -> low blood albumin (hypoalbuminemia) -> low oncotic pressure -> hydrostatic pressure pushes fluid out of capillaries -> generalized edema, often ascites.

Question 35

Dependent Edema: Mechanism

Answer 35

Weakened venous valves, lack of muscle contractions, gravity -> venous blood pools in lower extremities -> increased venous hydrostatic pressure -> fluid moves into ISF/ICF of ankles/feet.

Question 36

Pitting Edema: Description & Grading

Answer 36

Edema where pressure applied to a small area leaves an indentation. Severity graded (e.g., +1, +2, +3).

Question 37

Sequestered Fluids (Third-Spacing / Effusion): Definition & Types

Answer 37

Fluid accumulation in body cavities normally free of fluids (e.g., pericardial sac, peritoneal cavity, pleural space). Effusion: Can be transudate (serous filtrate) or exudate (contains blood, lymph, proteins, pathogens, inflammatory cells).

Question 38

Fluid Volume Overload: Common Causes & Mechanism

Answer 38

Heart failure (RAAS constantly cycles -> excess water retention -> increased hydrostatic pressure -> edema). SIADH (excess ADH -> excess water reabsorption -> dilutional hyponatremia).

Question 39

Syndrome of Inappropriate ADH (SIADH)

Answer 39

Condition causing excess ADH secretion -> excess water reabsorption by kidneys -> fluid volume overload and dilutional hyponatremia. Can occur in certain cancers, brain disorders.

Question 40

Dehydration: Definition & General Causes

Answer 40

State of diminished water volume in body; ICF deficit causes cell shrinkage; ECF volume also decreased. Causes: Reduced fluid intake, excessive fluid loss (illness, ADH issues, GI disorders, burns, fever, perspiration), hypovolemia.

Question 41

Dehydration Pathophysiology: Hyperglycemia Example

Answer 41

Uncontrolled diabetes -> high blood glucose (solute) -> raises osmotic pressure in ECF -> water shifts from ICF to ECF (cellular dehydration) -> increased ECF volume delivered to kidneys -> polyuria (excess urine) -> further dehydration.

Question 42

Physiological Response to Dehydration (Compensatory Mechanisms)

Answer 42

Osmoreceptors stimulate thirst. Baroreceptors sense low BP -> stimulate sympathetic nervous system (vasoconstriction, increased HR). Osmoreceptors stimulate ADH release (water reabsorption). Low kidney perfusion activates RAAS (Na+/water retention, vasoconstriction).

Question 43

Oliguria: Definition & Clinical Significance

Answer 43

Urine output less than 400 mL/day or less than 20-30 mL/hour in an adult. Risk of renal dysfunction as kidney needs to excrete ~400mL daily to clear waste products.

Question 44

Assessment of Fluid Volume Status: Daily Weight

Answer 44

Weight change of 2 pounds from one day to next likely due to fluid gain/loss (1 liter of fluid ~ 2.2 lbs or 1 kg).

Question 45

Assessment of Fluid Volume Status: Intake and Output (I&O)

Answer 45

Normal adult intake ~2L/day (1500 mL/m2). Intake: oral, IV, tube feedings. Output: urine, vomitus, wound/ostomy drainage, insensible losses (lungs, sweat, feces - ~1000mL/day, more with fever). Should be ~equal over 24h.

Question 46

Assessment of Fluid Volume Status: Vital Signs & Physical Signs (Dehydration)

Answer 46

Vital Signs: Tachycardia, hypotension, orthostatic hypotension (systolic drop =20 mmHg or diastolic =10 mmHg within 3 min of standing). Physical Signs: Thirst, dry mucous membranes, poor skin turgor (tenting), low/dark urine output.

Question 47

Assessment of Fluid Volume Status: Physical Signs (Fluid Excess)

Answer 47

Edema (pitting, ascites), moist mucous membranes, hypertension (possibly), weight gain, dyspnea (pulmonary edema), crackles in lungs.

Question 48

Electrolytes: General Importance & Na+/K+ Pump Role

Answer 48

Essential for enzymatic/hormonal/chemically mediated mechanisms (ATP generation, DNA/RNA synthesis, neural transmission, muscle contraction). Na+/K+ pump maintains K+ as main intracellular ion and Na+ as main extracellular ion, crucial for electrochemical gradients.

Question 49

Effect of Na+ & K+ Imbalances on Neuromuscular & Cardiac Function

Answer 49

Widely disrupts neural transmission. Body-wide muscular weakness, paresthesias. GI dysfunction (nausea, constipation, distention). CNS dysfunction (confusion, disorientation). Cardiac dysfunction (ECG changes, rhythm disturbances, postural hypotension), especially with K+ disruption.

Question 50

Role of Calcium Ions in Cardiac Muscle Contractility

Answer 50

Cardiac muscle contraction is largely dependent on calcium influx through voltage-gated calcium channels on the plasma membrane.