Unit 6: Kidneys, fluids, and electrolyte ILE 1 pt. 2

What goes in place of A on them chem 7 diagram?

sodium (Na)

What goes in place of B on them chem 7 diagram?

potassium (K)

What goes in place of C on them chem 7 diagram?

Chloride (Cl)

What goes in place of D on them chem 7 diagram?

bicarbonate/CO₂

What goes in place of E on them chem 7 diagram?

blood urea nitrogen

What goes in place of F on them chem 7 diagram?

serum creatine

What goes in place of G on them chem 7 diagram?

glucose

What goes in place of H on them chem 10 diagram?

Calcium (Ca)

What goes in place of I on them chem 10 diagram?

Magnesium (Mg)

What goes in place of J on them chem 10 diagram?

phosphorus (Phos)

What goes in place of K on them CBC diagram?

white blood cells (WBC)

What goes in place of L on them CBC diagram?

hemoglobin (Hgb)

What goes in place of M on them CBC diagram?

hematocrit (Hct)

What goes in place of N on them CBC diagram?

platelets (Plt)

fluid homeostasis

maintaining intracellular volume to facilitate tissue perfusion and oxygenation, ensures cellular functions

TBW

total body water

your TBW should be ___% of your total body weight

60% in men and 50% in women

the extracellular compartment is __ of TBW

1/3

intravascular fluid (plasma) makes up ___ of extracellular fluid

1/4

interstitial fluid (between cells) makes up ___ of extracellular fluid

3/4

the intracellular compartment makes up ___ of total body water

2/3

Mechanisms responsible for water/ fluid loss

excretion via urination (kidney), injury/trauma/disease, insensible fluid loss (exhalation, precipitation, defecation), alcohol, drugs, pharmaceuticals

capillary

thin semi-permiable membrane of endothelial cells

What is responsible for osmotic pressure?

large molecules and proteins

starling forces

influences of filtration rate along capillary

ligand gating

form of passive transport where channels open in response to ligand binding

voltage gating

form of passive transport where channel opens in response to a change in membrane potential

post-tanslational modification

channel gates in response to modification such as phosphorylation

Example of an active transport mechanism

Na, K, ATPase transporter

For the Na⁺, K⁺, ATPase active transporter α subunit has…

Na-binding site, phosphorylation site, and ATP-binding site

For the Na⁺, K⁺, ATPase active transporter extracellular portion has

K-binding site and ouabain-binding site

Osmosis

flow of water across cell membranes via simple or facilitated diffusion

how does the body maintain homeostasis in regards to osmosis?

pumps/transporters

hydrostatic pressure

force exerted by fluid against a wall that results in movement of fluid between compartments (ex: force due to pumping of the heart)

What forces plasma and nutrients out of the capillaries and into the surrounding tissue?

hydrostatic pressure

isotonic solution

same concentration inside and outside (no net movement)

Hypertonic solution

extracellular has an increased concentration than intercellular (net movement out of cell)

hypotonic solution

extracellular has a lower concentration than intercellular (net movement into the cell)

if you place a cell in an isotonic solution, it is likely to undergo

equilibrium

if you place a cell in a hypertonic solution it is likely to undergo

crenation (shrivel)

If you place a cell in a hypotonic solution it is likely to undergo

lysis (rupture)

What electrolytes are primarily extracellular?

Na, Cl, CA

what electrolytes are primarily intracellular?

K, Mg, PO4

What influenced transcellular fluid balance?

osmolality and tonicity

what is the primary organ of electrolyte-fluid balance?

kidney

Where is the thirst center located?

hypothalamus

A decrease in blood pressure causes

increased angiotensin II

when you have an insufficient amount of water in your body it

increases the osmolality of your blood

A patient presents to the emergency department with significant dehydration following several days of vomiting. Laboratory testing reveals an increased plasma osmolality. Which of the following structures in the hypothalamus is activated in response to the increased blood osmolality?

Osmoreceptors

Water follows?

Sodium!

Can you regenerate a nephron once it has been damaged?

no

kidney physiology

removes waste, regulates serum pH, regulates blood pressure, produces hormone responsible for red blood cell production, and regulates bone health

urine contains

95% water and 5% solutes

Glomerular filtration

water and solutes move from blood vessels of glomerulus to begin urine via diffusion (larger molecules like proteins and drugs cannot enter bowman’s capsule)

GFR

total amount of filtrate (mL) formed by all nephrons/min & used to approximate kidney function

What is the typical GRF

(120-130 ml/min)/1.73m²

How to determine GFR

a) administer a substance that is not metabolized and freely filtered and measure amount excreted in urine over a known time period (expensive)

b) use an endogenous substance that is not metabolized and is freely filtered like serum creatinine (SCr) or Cystain-C (cys-c) (estimated value)

reabsorption

movement of solutes and water from urine back into blood stream & regulated by diffusion, active transport, and cell membrane charge

Where are medications reabsorbed?

distal tubule and collecting duct

Where are water and solutes primarily reabsorbed?

throughout the nephron

Secretion

movement of water and solutes from blood into urine

What is always an active process and occurs in the PCT (and ion Channels)

secretion

Glomerulus

freely filters Na⁺ (water follows), C^-, K⁺, HCO₃, phos, Ca⁺²

the Proximal Tubule of a nephron reabsorbs

all of the glucose

majority of Na (water follows), Cl, K, HCO₃, Ca

some of phos

the Proximal Tubule of a nephron secretes

creatinine, H⁺, NH⁺⁴, some drugs

Which part of the nephron reabsorbs ~20% K, ~10% phos, ~20% Ca?

loop of henle

The descending limb of the loop of henle absorbs

water only

the ascending limb of the loop of henle reabsorbs

Na and Cl

Is impervious to water

What drug targets the loop of henle

loop diuretics

Where in the nephron is ~5% Na/Cl +water, ~10% phos, and ~20% Ca reabsorbed?

Distal convoluted tubule

What is secreted by the distal convoluted tubule?

K⁺ (via aldosterone), H⁺, NH₄⁺, and some drugs

What drug targets the distal convoluted tubule?

thiazide diuretics

The collecting duct of the nephron reabsorbs

Na⁺ and Cl^- , aquaporins allow for water movement, Ca⁺, and phos (via PTH)

What is secreted in the collecting duct

K⁺(via aldosterone), H⁺, NH₄⁺, and some drugs

What drug targets the collecting duct

aldosterone antagonists and vasopressin antagonists

how does aldosterone influence reabsorption?

binds to and stimulates ENaC → increased Na⁺ reabsorption → increased water reabsorption

how does aldosterone influence secretion?

it binds to and stimulates Na-K ATPase → increased K⁺ secretion

thiazide diuretics

is a weak diuretic used to treat HTN and edema

Block Na-Cl symporter of Distal convoluted tubule

Predictable ADRs: hyperglycemia, hyperuricemia, hypomagnesemia, hypokalemia, hypotension, hyponatremia, and dehydration

loop diuretics

used to treat volume overload and HTN

Block the Na-K-2Cl cotransporter at the ascending loop

unpredictable ADRs: hearing loss

predictable ADRs: hypocalcemia, hyponatremia, hypokalemia, hypomagnesemia, hypotension, dehydration

mineralocorticoid receptor antagonists

used to treat resistant HTN resistant and ascites (fluid build up in abdominal cavity)

• unpredictable ADRs: rash, gynecomastia, hirsutism, sexual dysfunction, dysmenorrhea, headache

• predictable ADRs: hyperkalemia, and hypotension

Antidiuretic hormone (ADH)

released by pituitary gland to regulate water in the kidneys → binds to vasopressin V (ADH) receptor → cAMP activated → aquaporin channel proteins produced and inserted into apical membrane → water reabsorbed via osmosis

vasopressin receptor antagonists

prevent ADH from binding ADH/ vasopressin receptor → no G-protein release → no aquaporins → no water reabsorption

• predictable ADRs- dehydration, frequent urination, decreased urine osmolality

Crystalloids

solutions of small molecules/ electrolytes in water that are able to distribute into tissues (ex: saline, dextrose, LRS)

Colloids

dispersions of large organic molecules like proteins (albumin) or complex polysaccharides (dextrans, starches); remain in intravascular space

5% dextrose in water (D5W) tonicity

hypotonic

0.45% NaCl (half normal saline) tonicity

hypotonic

0.9% NaCl (normal saline) tonicity

isotonic

0.9% NaCL electrolytes

Na: 154 | Cl: 154

serum osmolality

concentration of dissolved particles (ex: electrolytes and glucose) in blood

• used as an indicator of the body’s water balance

• heavily influenced by Na

• estimated serum osmolality

Isotonic saline has what effect on intracellular volume>

no change

Isotonic saline effect on extracellular volume

increase

Isotonic saline effect on serum osmolarity

no change

Hypotonic saline effect on intracellular volume

increase

Hypotonic saline effect on extracellular volume

increase

Hypotonic saline effect on osmolarity

decrease

Hypertonic saline effect on intracellular volume

decrease

Hypertonic saline effect on extracellular volume

increase

Hypertonic saline effect on serum osmolarity

increase

What are some labs values to consider when assessing a patient’s fluid status

electrolytes, serum-urine osmolality, glucose, protein, lipids, BUN:SCr

hypovolemic

too little volume

decrease BP and BW, increased HR, Dry mouth, thirst, pale gums, dark urine