Chapter 10. Micronutrients Involved in Fluid and Electrolyte Balance
Chapter Review
IMPORTANT: Key Takeaways
- Osmoregulation is the process by which fluid balance is maintained (to keep fluids from becoming too diluted/concentrated). Water moves from an area of high solute concentration to an area of low solute concentration in a process known as osmosis.
- Water serves as a universal solvent, allowing for the dissolution of more substances than any other fluid. It also acts as a medium for chemical reactions. Additionally, water plays crucial roles in regulating blood volume and pressure, acting as a lubricant and shock absorber for supporting organs, and facilitating thermoregulation by distributing heat and equalizing body temperature.
- When blood volume is low, kidney cells detect decreased pressure and secrete the enzyme, renin. Renin travels in the blood and cleaves another protein into the active hormone, angiotensin which targets three different organs to rapidly restore blood volume and blood pressure
- Sodium is essential for maintaining fluid balance, transmitting nerve impulses, and facilitating nutrient absorption and reabsorption through the sodium-potassium pump. It also regulates blood pressure and acid-base balance. Processed and prepared foods are common dietary sources of sodium. Excessive water loss through sweat, which can occur during extreme environmental conditions or strenuous physical labor, can be replenished by consuming snacks. Hyponatremia, characterized by low blood sodium levels, is often caused by excessive water consumption and can lead to symptoms such as nausea, muscle cramps, confusion, and in severe cases, death.
- Potassium plays a role in nerve impulse transmission, protein synthesis, energy metabolism, platelet function, and acid-base balance. It is abundant in fruits, vegetables, and meats. Hypokalemia, resulting from low potassium intake or high sodium intake, is commonly caused by diuretics that increase water excretion. Symptoms may include weakness, cramps, constipation, and in severe cases, it can be fatal. Hyperkalemia, characterized by extremely high levels of potassium, typically stems from kidney dysfunction and can lead to cardiac arrest.
- Chloride plays a role in fluid balance and acid-base balance. The primary dietary sources of chloride are foods containing sodium chloride (ie. tomatoes, lettuce, and olives). Low dietary intake of chloride can cause symptoms similar to hyponatremia (ie. nausea and headache). Cystic fibrosis is an inherited disease caused by a mutation in a protein that transports chloride out of the cell. It can cause symptoms such as salty skin, poor digestion, mucus accumulation, liver damage, and infertility.
- Phosphorous is a structural component of cell membranes, DNA and RNA, and is involved in energy production and fluid and acid-base balance. Some dietary sources of phosphorous include meat, fish, dairy products, processed foods, and beverages. Individuals suffering from alcoholism, premature infants, the elderly with a poor diet, and those with a vitamin D deficiency may be at risk of phosphorous deficiency. The PTH stimulates renal excretion of phosphate so it doesn’t accumulate to toxic levels.
Practice Questions
- What is the process of osmoregulation?
- What is the difference between hypertonic, hypotonic, and isotonic solutions?
- Why is water called the universal solvent?
- Explain how the body regulates blood pressure via the renin-angiotensin-aldosterone system.
- Why is water an ideal medium for chemical reactions?
- Considering the protective role mucus plays in the body, how might disruptions in its production impact the body’s overall health?
- Explain how the temperature set point of the body is maintained even when exposed to cooling temperatures.
- How do increased blood sodium concentrations drive us to drink water? Explain the steps involved in this process.
- Explain how the nervous and endocrine systems interact to regulate water output.
- Sally is training to participate in an ultramarathon in extremely hot weather. What are some things Sally can do to prevent dehydration, hyponatremia, and heat stroke?
- Which populations may benefit from lowering their salt intake? Why? How can this be achieved using salt substitutes and alternative seasonings?
- What are the functions of potassium in the body?
- What are common dietary sources of chloride?
- Which individuals may be at risk of experiencing phosphorous toxicity? What are some of the observable signs of phosphorous toxicity and how can this be prevented?
- The DASH-Sodium trial investigated the effects of a specified eating plan with or without reduced sodium intake. The results of the study showed that following the DASH diet reduced blood pressure among participants. Why is it that the reductions in blood pressure cannot be attributed to decreases in salt intake alone?
