Exam 3 (Electrolytes) Flashcards
Cations vs Anions
Cations: positively charged particles
Anions: negatively charged particles
What are electrolytes?
Soluble substances (ions or minerals that have a charge) found in liquid serum or plasma
What are the general overall functions of electrolytes?
Coagulation, Energy production, cell metabolism, skeletal/cardiac muscle function, volume and fluid gradients between cells/blood/tissues
Humans are predominantly ______, making up ______% of body weight.
Water; 50-75%
Water % ______ with age.
Declines
Do women or men have less % water?
Women
Do obese people have less or more water than non-obese people?
Less
Intracellular fluid and % of total water
Fluid found inside of all cells - appx 66% of total water weight
Extracellular fluid + 2 groups; % of total water?
Fluid found outside of cells that can be broken into 2 groups:
Intravascular: found in vasculature; plasma portion of whole blood
Interstitial: fluid surrounding the cells
Active transport
Moves substances against concentration gradient and requires ATP
Passive transport
AKA diffusion; moves substances with the concentration gradient and requires no ATP
What is the major extracellular cation?
Sodium
What is largely responsible for the osmolality of plasma?
Sodium
What is the reference range for serum sodium?
135-145 mmol/L
How many Na ions are pumped out of the cell for every 2 K ions in the cell?
3 Na per 2 K
What is plasma sodium heavily regulated by?
water intake and loss of water through sweat and renal functions
If plasma sodium osmolality is high, what occurs?
Hypothalamic thirst centers in the brain drive increased water consumption and ADH is released to increase water reabsorption from urine
What is hyponatremia usually due to?
Increased sodium loss (decreased aldosterone, K deficiency)
Increased water retention (renal failure, nephrotic syndrome)
Water imbalance (excessive water intake, increased ADH)
What is a critical sodium level?
Hyponatremic <120 mmol/L
How are sodium levels regulated?
Water intake and water loss (aldosterone increases sodium reabsorption and ADH increases water reabsorption)
Signs and symptoms of Hyponatremia
GI distress, neurological symptoms (weak, headache, seizure, ataxia)
What is Hypernatremia caused by?
excessive water loss (diabetes insipidus, diarrhea, profuse sweating)
increased sodium retention (increased aldosterone)
Decreased water intake
Is Hypo or Hypernatremia more critical?
Hyponatremia
How can we detect sodium levels in the lab?
Serum/plasma (lithium heparin tube, green top) using Ion Selective Electrodes (ISE)
Can also test urine
Does hemolysis impact sodium levels? Why?
Not really because sodium is located outside of cells
Direct vs Indirect ISE
Direct ISE uses undiluted sample using whole blood
Indirect ISE uses diluted sample using plasma or serum
What is the major intracellular cation?
Potassium
Functions of potassium in the body
Regulation of neurons for action potentials, heart contractions, ICF volume, Hydrogen ion regulation, skeletal muscle contractions
How are potassium levels related to Sodium and Hydrogen ions?
If K ions decrease, ICF increases Na and H levels which decreases ECF levels of Na and H (leads to hyponatremia and alkalosis of blood pH)
What is the normal reference range for serum K?
3.5-5.1 mmol/L
What is potassium regulated by?
The renal system with tubular secretion and absorption (Nearly all K is reabsorbed in the PCT)
What are the 3 influences of potassium distribution between the ICF, ECF, and urine?
Na/K pumps, Insulin, and Catecholamines
How does exercise affect potassium levels?
Potassium is released from skeletal muscles during exercise due to firing multiple action potentials which could raise potassium levels greatly
Does hemolysis affect potassium levels?
Yes
What can hypokalemia lead to?
Decreased muscle contractions leading to paralysis and decreased HR
What can cause hypokalemia?
Renal dysfunction, cellular loss due to alkalosis or insulin overdose, decreased intake of fluid, gastrointestinal loss
What can hyperkalemia lead to?
Increased action potentials (cells are easier to excite) leads to muscle fatigue, paralysis, arrhythmia, death because muscle cells cannot repolarize properly
What are the causes of hyperkalemia?
Decreased renal excretion (renal failure)
Cellular shift (blood acidosis, hemolysis)
Increased intake
Collection error
How does improper collection affect potassium levels?
It can increase them because of increased hemolysis (cells release their contents into the blood stream)
Signs of hyperkalemia
Muscle weakness, tingling, numbness, because cells are not contracting appropriately – can lead to cardiac arrest
What is the most abundant extracellular anion?
Chloride
What is the function of Chloride?
Maintains osmolality, blood volume, electroneutrality between ECF and ICF, plays a role in regulating HCO3 and Na levels
What is the common route of elimination of chloride?
Via the kidneys and the skin as sweat
What is the reference range for Chloride levels in serum?
98-107 mmol/L