Chem Ppt flashcards, Unit 3 What is the function of electrolytes?

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Chem PPT Flashcards, Unit 3

What is the function of electrolytes?

Run maintenance of water homeostasis, maintenance in acid-base balance and muscle functions as well as serves as cofactors for enzymes.

What is the major cation of extracellular fluid?

Sodium (Na+)

What does Sodium determine in the extracellular fluid?

The osmolality.

When is sodium excreted in the urine?

When serum sodium exceeds 110-130 mmol/L

What happens when serum levels are below 110 mmol/L?

All the sodium in the glomerular filtrate is virtually reabsorbed in the proximal and distal tubules, a process that is influenced by aldosterone.

Sodium specimens consist of…?

And should be stored at…?

Serum, plasma and urine specimens and may be stored at 4°C or may be frozen. Lipemic samples need to be ultracentrifuged.

What are the methods of measuring sodium?

Atomic Absorption Spectrophotometry (AAS),

Sodium Ion selective electrode (ISE), and Spectrophotometry.

What is the major intercellular cation?

Potassium (K+)

How are high concentrations of potassium maintained?

Na+K+ adenosine triphosphate (ATP) pump which is fueled by oxidative energy and continually transports K+ into the cell against a concentration gradient.

Does potassium exhibit a renal threshold?

No, however it is excreted into the urine even in K-depleted states.

What are some of the functions of potassium?

Regulation of neuromuscular excitability (both hypo- and hyperkalemia can cause muscle weakness) and contraction of the heat and cardiac rhythm (decrease K+ increases cardiac excitability and often leads to arrhythmia. High K+ slows the heart rate).

How does potassium affect acid-base status?

In hypokalemic states, sodium and H+ ions move into the cell to replace K+. The H+ concentration is therefore decreased in the ECF=alkalemia (reverse is true of hyperkalemia).

What should the concentration of K+ be?

In plasma and whole blood the concentration is 0.1-0.7 mmol/L lower than those in serum.

How does the release of K+ affect values?

As few as 0.5% K+ of RBCs will increase K+ values by 0.5 mmol/L. An increase of K+ of 0.6% has been estimated for every 10 mg/L of plasma hemoglobin (Hb) caused by hemolysis.

What causes glycolysis to be inhibited and the energy-dependent Na+, K+-ATPase will not maintain the Na+/K+ gradient?

When a whole blood specimen is maintained at 4°C versus 25°C before separation.

What does a K+ leakage from erythrocytes and other cells cause?

It causes an increase in plasma K+.

What causes falsely decreased K+ value?

When an un-separated sample is stored at 37°C because glycolysis occurs and K+ shifts intracellularly. Leukocytosis will initially cause falsely decreased K+ concentration at room temp.

What are reliable determinations recommended for K+?

Collect blood with heparin, maintain near 25°C and separate the plasma within minutes by high-speed centrifugation without cooling.

What can falsely increase K+ concentration?

Skeletal muscle activity as a result of repeated clenching of fist and application of the tourniquet.

What are methods for the determination of sodium and potassium?

Ion selective electrodes (ISE) and spectrophotometric methods.

What is the major anion of the extracellular fluid?

Chloride (CI-)

What is the function of chloride?

Maintains the water distribution, osmotic pressure, and anion-cation balance in the ECF.

Where is chloride absorbed?

In the intestinal tract and is excreted by kidneys.

What specimens contain chloride?

Serum, plasma, urine and sweat.

How is chloride affected by hemolysis, change in posture or stasis, and tourniquet use?

It is not affected.

Methods for chloride determination?

Coulometric-amperometric titration of chloride (cotlove chloridometer technique) and ion selective electrode methods.

Measurement of sweat chloride (sweat testing)?

Cystic fibrosis, the most common lethal genetic disorder of Caucasian population characterized by increased sweat chloride concentration.

Sweat testing and newborn screening…

Are performed in conjunction, with a positive screening test are referred to as a quantitative sweat chloride test.

What phases are done for sweat testing?

Sweat stimulation by pilocarpine electrophoresis, collection of sweat, qualitative or quantitative analysis of sweat, sodium or conductivity.

What is an abnormal infant sweat testing result?

≥60 mmol/L = indicative of CF

Bicarbonate is another name for:

Total carbon dioxide

True or False: Plasma or serum can be used to measure bicarb?


True or False: Sample must be centrifuged in an open tube?

False, be must be unopened

True or False: Ambient air contains far more CO2 than plasma?


If CO2 is allowed to escape from the sample into air, ___to___ mmol/L will be lost per hour.

4 - 5

Two ways of measuring total CO2 are acidification and ____


Acidification is a(n) ___ electrode based method?


Define osmometry:

a technique for measuring the concentration of solute particles that contribute to the osmotic pressure of a solution.

Define osmotic pressure:

the pressure required to stop osmosis through a semipermeable membrane between a solution and pure solvent.

Define osmosis:

process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one.

Name 4 colligative properties of solutions:

1. Increased osmotic pressure
2. Lowered vapor pressure
3. Increased boiling point
4. Decreased freezing point

Colligative properties of solutions are all directly related to:

total number of solute particles per mass of solvent.

The term osmolality expresses:

concentrations relative to mass of the solvent.

The term osmolarity expresses:

concentrations per volume of solution.

Plasma and urine osmolality is useful in the assessment of:

Electrolyte and acid-base disorders

The 4 major osmotic substances in normal plasma are:

Na+ / Cl- / glucose / urea

The Henderson-Hasselbalch equation defines pH as:

The negative log of the H+ activity

The Henderson-Hasselbalch equation is widely used to calculate the ___ point of proteins.


Total O2 content (cdO2) is:

the sum of the concentrations of hemoglobin-bound O2 (oxyhemoglobin) and of dissolved O2 (cdO2).

Oxyhemoglobin (O2Hb) is defined as:

erythrocyte hemoglobin with O2 reversibly bound to Fe2+ of its heme group.

Define the following terms:

pO2 =

pCO2 =

ctCO2 =

HCO3 =

cdCO2 =

pO2=partial oxygen pressure.

pCO2=partial carbon dioxide pressure.

ctCO2=total concentration of carbon dioxide.


cdCO2=concentration of dissolved carbon dioxide.

What specimen is used for blood gas analysis?

Whole blood.

What is the only clinical reason for an arterial draw?

PO2 value

PO2 is generally 60 mm Hg ___ in venous blood.


PCO2 is 2-8 mm Hg ___ in venous blood.


Arterial and venous specimens for blood gas analysis are best collected:

anaerobically with lyophilized heparin using glass syringes

Lyophilized heparin is preferred to liquid heparin because:

liquid heparin dilutes the sample, and the effect is greatest when the syringe is not completely filled

3 effects of exposing blood gas samples to the air:

Increase in pO2, increase in pH, decrease in pCO2

The pCO2 in blood is much ___ than the pCO2 in the air.


On exposure of blood to the air, the total CO2 and the pCO2 both ___


On exposure of blood to the air pO2 __


In blood gas samples, clots are ___


In blood gas samples, air bubbles cause (increase or decrease) in total CO2, pCO2, pH, pO2.

Decrease, decrease, increase, increase.

What are the reasons for the following changes in pCO2, pH and pO2 in a sealed specimen left at room temperature for 2 hours:

Increase in pCO2 as a result of continued metabolism, decrease in pH due to increased production of carbonic acid and lactic acid during glycolysis, decrease in pO2 because O2 is consumed during prolonged standing.

Arterialized capillary blood is an acceptable alternative to arterial blood but it has to be:

freely flowing cutaneous blood.

The first drop is discarded and the subsequent free forming drops should be taken up in a:

capillary collection tube containing lyophilized heparin

Transport and analysis of specimen should be within ___ of collection.


Because electrodes are not stable over long periods of time, frequent calibration of ___, ___ and ___ is required:

Proper maintenance includes:

pH, PCO2, and PO2

-meticulous care.

-adherence to the manufacturer's procedures.

-control of the equipment.

-proper collection and handling of specimens.

-the frequency with which maintenance should be maintenance = volume of analysis performed.

Good quality assurance includes:

-proper maintenance of the instrument.

-use of control materials.

-verification of electrode linearity.

-checking of barometer accuracy.

-accurate measurement of temperature.

External quality assurance (proficiency testing) mandated by:


A hormone is:

a chemical substance produced in the body by an organ, cells of an organ, or scattered cells that has a specific regulatory effect on the activity of an organ or organs.

Hormones are produced at one site in the body and exert their action(s):

at distant sites through what is called the endocrine system.

Paracine action is:

action of certain hormones that exert their effect locally on nearby cells.

Autocrine action is:

action of certain hormones that exert their effects on the cells of origin.

Adrenocorticotropic hormone (ACTH), insulin, parathyroid hormone (PTH) are examples of ___ or ___ hormones

Polypeptide or Protein

This class of hormone is soluble in:


This class of hormone has a half-life of ___ to ___.

≤10 to 30 minutes

This class of hormone initiates response by:

Binding to cell membrane receptors and exciting the second messenger system.

Cortisol and estrogen are 2 examples of _____ hormones.


Steroid hormones are hydrophobic and water insoluble.


Steroid hormones circulate in plasma, reversibly bound to transport proteins with only a small fraction free or unbound and available to exert physiological action.


What is the half-life of steroid hormones?

30-90 minutes

How do steroid hormones enter the cell?

Passive diffusion

What are 2 examples of amino acid-related hormones?

Thyroxine and catecholamines

Amino acid-related hormones are water soluble.


Amino acid-related hormones interact with membrane associated receptors and use a second messenger system.


Amino acid-related hormones circulate in plasma bound to ______ or _______

Proteins, free

Estrogen and androgen are examples of ______ hormones.


What is the ability or tendency of an organism or cell to maintain internal equilibrium by adjusting its physiological processes?


In response to a glucose load, _____ is released from the ______.

Insulin, pancreas

What is responsible for regulating the dispersal of glucose into cells for the metabolism necessary to produce energy?


What are the counter regulatory hormones that regulate glucose concentration?

Glucagon, cortisol, epinephrine, growth hotmone and incretins

What are some examples of incretins?

GLP-1 and GIP

What is GLP-1?

Glucagon-like peptide 1

What is GIP?

Gastic inhibitory pepide

What is CaSR?

Calcium-sensing receptor

The CaSR on the parathyroid gland recognizes the circulating level of ionized calcium and regulates the synthesis and secretion of ____.


What is PTH?

Parathyroid hormone

PTH enhances renal tubular reabsorption of ?


PTH catalyzes the synthesis of renal hormone _____ to increase intestinal absorption of calcium.


The metabolism of water and electrolytes is regulated by _____, _______, and ______.

Aldosterone, renin, vasopressin

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