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NUTR 322: Final
Magnesium, Potassium, Sodium, Chloride, and Other Minerals Info
| Question | Answer |
|---|---|
| How is magnesium distributed in the body? | cells! Magnesium mostly lives in the cells |
| Why is magnesium distributed the way it is? | Mg has mostly intracellular functions- working with proteins, enzymes, and transcription factors. |
| Where else is magnesium besides the cells? | There is minimal magnesium in the blood plasma. |
| What are the food sources for Magnesium? | Protein enriched foods! Nuts, seeds, legumes, lentils, whole grains, green leafy vegetables, spices, dairy; "hard" tap water |
| What is to be noted about "hard" tap water? | It is more mineralized; areas that have less filtered water have less chronic illness and disease |
| What is utilized for magnesium supplements? | magnesium salts |
| How does food processing effect magnesium in food? | Ultra food processing reduces magnesium content- specifically B vitamins and minerals |
| Explain saturable absorption of magnesium | for LOW intake; carrier-mediated active transporter utilizes TRPM6 (dietary, new Mg) and TRPM7 (urinary reabsorption as urine excretes) |
| Explain simple diffusion absorption of magnesium | for HIGH intake; usually occurs with supplementation |
| How much of dietary magnesium is absorbed? | 30-60% |
| Does magnesium have a transporter? | No |
| How does magnesium transport? | Mg crosses the brushborder into enterocyte via TRPM6. (Mg can also go in-between cells w/o a transporter, because Mg has a + charge. Mg is pumped out of cell across the basolateral by ATPase (sodium dependent). Sodium is pumped into cells and ATP to ADP. |
| What are the percentages of Magnesium and transport style? | 50-55% Mg is freely transported 20-30% Mg is bound to albumin or globulin (protein) 5-15% Mg moves with ions (negatively charged) |
| Why is magnesium transport so critical? | Mg has a narrow safe range: 1.6-2.2 mg/dL This range is maintained by GI absorption, renal excretion, and transmembranous cation flux If Mg levels are off, check these things! |
| How does parathyroid hormone interact with magnesium? | Increases magnesium absorption, decreases renal excretion, decreases bone resorption |
| What other body systems contribute to magnesium? | Kidneys: control Mg losses in response to plasma concentrations Bones: provide a reservoir - this reflects PTH response -- To be noted: plasma concentrations can be maintained at expense of bones |
| How is magnesium excreted? | Through urine: depends on plasma concentrations -- Good biological sample to measure and assess Through feces: mostly unabsorbed Through skin: some Mg, through sweat |
| Function #1 of magnesium | Bone lattice and surface (55-60% of total Mg) |
| Function #2 of magnesium | More than 300 enzyme reactions as structural cofactor or allosteric activator -- Allosteric activator: protein, enzyme, transcription factors Mg binds to enzyme, changing its confirmation and activating it |
| Mechanisms of action for magnesium? | 1. cellular energy and metabolism 2. Nucleic acid and protein synthesis 3. Second messenger systems 4. ion channels |
| Magnesium: cellular energy and metabolism | Anion charge metabolism - Mg (+ charged) can stabilize negatively charged ions Work with organic polyphosphates - ATP and ADP, for example Work with multisubstituted phosphates of sugars -IP3 (2nd messenger molecule), RNA, DNA, carboxylases |
| Magnesium: nucleic acid and protein synthesis | Glycolytic pathway - Mg must be present to stabilize ATP in its conversion to ADP -- Everywhere ATP/ADP is in the glycolytic pathway, Magnesium is present! |
| Magnesium: second messenger systems | cAMP: For reaction cascade, Mg must be present. Two phosphates are lost by adenylate cyclase, then cyclic amp moves the location to 5 prime IP3: Mg aids reaction cascade. PI to PIP to PIP2 to IP3 Magnesium required- these reactions involve ATP to ADP |
| Magnesium: ion channels | Magnesium deficiency leads to cellular Potassium depletion - This is due to modulation of Sodium/ Potassium- ATPase pump - Without magnesium, the pump loses efficacy - Direct impacts with potassium does for the body |
| Magnesium ion channels (steps) | 1. magnesium deficiency 2. Intracellular calcium rises - Too many muscle contractions - Can cause stroke if severe and prolonged 3. muscle cramps, hypertension, coronary/ cerebral vasospasm |
| Magnesium deficiency | Common in hospitalized people underestimated in common population Plasma conc. may seem normal at expense of tissue conc. Mg is mostly needed at tissues for cofactor roles BUT Mg will leave tissues to go to plasma to maintain equal parts |
| Magnesium deficiency factors | Inadequate intake Excess alcohol use Malabsorptive disorders Medications Uncontrolled diabetes and metabolic syndrome -- 2 way street– uncontrolled diabetes and Mg deficiency They contribute to each other in a cycle |
| RDA value of magnesium | 19-30 years: men- 400mg, women/lactation- 310mg, pregnancy-350mg 31+ years: men-420mg, women/lactation- 320mg, pregnancy- 360mg |
| RDA value of phosphorus | 19+ years: 700mg for all |
| AI value for sodium | 1500mg (3.8g of salt) |
| AI value for Chloride | 2300mg |
| AI value for Potassium | 4700mg |
| AI value for Calcium | 19-50 years: 1000mg 51+ years: 1200mg |
| Where is sodium found? | 30% found on bone surface, 70% is in circulation |
| where is chloride found? | 88% extracellular fluid, 12% intracellular fluid |
| where is potassium found? | primarily stays inside cells |
| where is magnesium found? | mostly lives in cells, #1 abundance in cells |
| where is calcium found? | 99% in bones and teeth, 1% in fluids |
| where is phosphorus found? | 98% intracellular, 2% extracellular |
| How do the RDA/AIs of Na, K, Cl, and Mg compare to those of Ca and P? | The RDA/AIs for NA, K, Cl, and Mg are much higher than those for Ca and P because the first four minerals listed are utilized for numerous roles in the body. Ca and P have specific roles (bone formation, signaling, etc.) and only need concentrated amounts |
| What are the definition of macrominerals? | Macrominerals (major minerals) are essential dietary minerals that the body needs in relatively large amounts, 100mg or more per day. Play crucial role in body functions, bone health, fluid balance, nerve/muscle function |
| What is the UL for sodium? | 2300mg (1 teaspoon) |
| What is the UL for potassium? | none |
| what is the UL for chloride? | 3.6g |
| what is the UL for magnesium? | 350mg |
| how is the UL set for sodium? | the UL is set for sodium by evaluating blood pressures and seeing which sodium intakes caused changes (unhealthy, raised BP) |
| hyperkalemia | high blood potassium levels - K+ is higher than 5.5 mmol/L -- membrane depolarizes, causes muscle weakness, flaccid paralysis, and cardiac dysrhythmias MEDICAL EMERGENCY |
| hypokalemia | low blood potassium levels, k+ is lower than 3.5 mmol/L - membrane hyperpolarizes, decreases excitability of nerves and muscles, results in muscle weakness, and decreased contractibility |
| what is the average american intake of Na and K? | Na: 3-5g/day K: 3,300mg/ day |
| does the average american meet the AI for Na and K? | Na: Yes. Americans take in more than they need to. K: No. The daily value is 4700mg. |
| health claim associated with sodium | high sodium intake is linked to increase blood pressure, which elevates the risk of cardiovascular disease, stroke, and heart failure |
| health claim associated with potassium | plays crucial role in maintaining overall health,- blood pressure regulation, bone health, muscle function, manage blood glucose levels, support fertility, prevent kidney stones, reduce risk of stroke and cardiovascular |
| health claim associated with chloride | vital electrolyte that plays a crucial role in maintaining fluid balance, pH levels, nerve/muscle function. also helps with stomach acid production (essential for digestion) |
| sodium food sources | added salt, processed foods |
| potassium food sources | unprocessed foods, some fruits and vegetables, legumes, nuts, and seeds |
| chloride food sources | salt, eggs, fresh meat, seafood |
| what is cystic fibrosis? | a genetic disease that impacts the lungs, impacting osmolarity. chloride gets into lumen, lowering osmolarity. this leads to less water in the lungs and more blockages. this creates thick mucus in the lungs and susceptibility to lung infection |
| what is the genetic cause for cystic fibrosis? | CFTR gene mutation |
| physiological functions of sodium | 1. a major determinant of osmolarity and extracellular fluid volume 2. electrochemical gradient is important for other nutrients transport |
| sodium: determinant of osmolarity and extracellular fluid volume | changes sodium balance will change osmolarity, causing cascade effect. osmolarity receptor signals high osmolarity, signals thirst mechanism (then you drink water), ADH stimulates water retention to balance it out to stop osmosis |
| sodium: electrochemical gradient is important for other nutrients transport | sodium is higher in lumen cells and lower in intestinal cells. when sodium travels to areas in lower concentration, it can take other components with it like glucose, amino acids, proteins, etc |
| physiological functions of k, na and cl | determinants of resting membrane potential and action potential (the excitability of nerve and muscle cell) |
| resting membrane potential | microelectrode inserts into cell, potential difference between inside and outside of cell can be noted. |
| how is resting membrane potential determined? | by the difference in ion concentration between inside and outside of cell |
| why do na and k play the most important roles in generating the membrane potential? | they are major ions |
| quote about RMP from class | "the concentration differences & the membrane is more permeable to K than to Na, more efflux of K+ than influx of Na+. the RMP is negative inside relative to the outside of the membrane. (-70mV for many neurons and -90mV for skeletal muscle fibers)" |
| action potential | membrane potentials are depolarized or hyperpolarized depending on direction of current flow across cell membrane |
| stimulation causes... | depolarization |
| why does depolarization occur with action potentials? | occurs because of sudden influx down the concentration gradient for Na and K |
| How do Na+ influx and K+ efflux move? | through voltage-gated Na and K channels, play critical roles in action events - sodium channel closes, potassium channel opens -- this happens in milliseconds |
| How does the hypothalamus (ie ADH) and the renin-angiotensin-aldosterone system work to control the kidney’s function? | osmosis |
| what is the osmosis process? | High solute on one side & low on the other. Equal solvent on both. The difference in solute btwn the sides causes movement in solvent from low side to high side. This allows solutes to spread out & creates equal osmolarity of the semi permeable membrane. |
| how does the osmosis process work? | Membrane allows solvent to pass through but not absolute. The solute is typically Na and K. Any changes in Na will alter osmolarity because more or less solute will be present. |
| what do osmoreceptors do in osmosis? | When osmolarity changes, osmoreceptors found in paraventricular nuclei of the hypothalamus sense this and relay signals downstream to ADH. |
| what does ADH do in osmosis? | ADH (antidiuretic hormone) in the posterior pituitary restore osmolarity due to this signal and can cause more water retention, preventing urination to balance ECF out and stop osmolarity. |
| what is the kidney role for maintaining the balance of these minerals? | the kidney is responsible for regulation |
| how does the kidney regulate? | 3 processes: filtration, reabsorption, & secretion Na loss controlled by reabsorption rate from filtrate by tubular cells; K loss controlled by secretion rate into lumen by tubular cells; if K concentration is abnormal = abnormal secretion/ excretion |
| What is essential or primary hypertension? | Essential or primary hypertension has an unknown cause. |
| how is hypertension related to the intake of Na? | Increase in sodium intake raises blood pressure. Increasing sodium leads to water retention, which causes volume expansion and vasoconstriction. |
| how is hypertension related to the intake of K? | Higher potassium intake reduces blood pressure. Potassium promotes the urinary excretion of sodium, calcium, and magnesium via urine. This process lowers blood pressure because both the minerals and water are being excreted. |
| how is hypertension related to the intake of Mg? | Insufficient intake leads to higher blood pressure. |
| how is hypertension related to the intake of Ca? | Insufficient intake leads to higher blood pressure. |
| Who will benefit from sodium reduction or calcium supplementation in terms of blood pressure? | Those who are predisposed to suffer from hypertension would benefit from sodium reduction or calcium supplementation- such as being over the age of 65, african americans, obese, diabetics, and the hypertensive. |
| What are the suggested mechanisms for these relationships? I.e. the mechanisms for each mineral to impact blood pressure. | Sodium: decrease intake to decrease blood pressure Potassium: increase intake to decrease blood pressure Magnesium: increase intake to decrease blood pressure Calcium: increase intake to decrease blood pressure |
| nacl retention causes | by rapid ingestion of large amount of salt or too-rapid saline infusion |
| nacl retention health consequence | edema |
| nacl deficiency causes | use of diuretics that inhibit NaCl reabsorption, or presence of an osmotic solute (glucose in diabetes) |
| nacl deficiency health consequence | orthostatic hypertension and increase in heart rate |
Created by:
lcorlew1
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