Utilizing knowledge from your learning and assigned readings, respond to the following questions:
- The maintenance of normal volume and composition of extracellular and intracellular fluids is vital to life. List and briefly describe the kinds of homeostasis involved.
- Why does maintaining fluid balance in older people require a higher water intake than in a normal, healthy adult under age 40?
- Why does potassium concentration rise in patients with acidosis? What is this called? What effects does it have?
- Saline solution is used to reverse hypotonic hydration. Are body cell membranes permeable to saline? Explain your response.
- Explain the renin-angiotensin mechanism.
- Explain how ADH compensates for blood that contains too many solutes.
Expert Solution Preview
Introduction:
Fluid and electrolyte balance is crucial for the proper functioning of the human body. It is necessary for proper cellular function, and perturbations in fluid and electrolyte balance can lead to significant health problems. As a medical professor, it is essential to teach students these concepts effectively to help them understand the importance of maintaining fluid and electrolyte balance in the human body.
1. The maintenance of normal volume and composition of extracellular and intracellular fluids is vital to life. List and briefly describe the kinds of homeostasis involved.
The kinds of homeostasis involved in maintaining normal volume and composition of extracellular and intracellular fluids include:
a. Water Balance: The balance between water intake and output is crucial in maintaining fluid homeostasis. The kidneys play a vital role in regulating water balance by reabsorbing and excreting water as necessary.
b. Electrolyte Balance: Electrolytes are essential ions in the body that carry an electrical charge. Maintaining the appropriate balance of electrolytes, including sodium, potassium, calcium, and magnesium, is essential for proper cellular function.
c. Acid-Base Balance: The blood’s pH must be maintained within a narrow range to ensure proper cellular function. The kidneys and lungs play a vital role in maintaining the body’s acid-base balance.
2. Why does maintaining fluid balance in older people require a higher water intake than in a normal, healthy adult under age 40?
Older individuals have decreased kidney function, which can lead to decreased water efficiency and changes in fluid balance regulation. As a result, they require a higher water intake to maintain proper fluid balance than a normal, healthy adult under age 40.
3. Why does potassium concentration rise in patients with acidosis? What is this called? What effects does it have?
In acidosis, the pH of the blood decreases, leading to an increase in the production of hydrogen ions. To balance this increase in hydrogen ions, potassium ions move out of the cells and into the extracellular fluid, leading to an increase in the serum potassium concentration. This phenomenon is called acidemia. Increased potassium concentrations can lead to muscle weakness, cardiac arrhythmias, and even cardiac arrest.
4. Saline solution is used to reverse hypotonic hydration. Are body cell membranes permeable to saline? Explain your response.
Body cell membranes are permeable to water but are not permeable to saline. Saline has a high concentration of sodium and chloride ions, which cannot easily cross the cell membrane. Hence, saline solution administration leads to water moving into the cells, thereby reversing hypotonic hydration.
5. Explain the renin-angiotensin mechanism.
The renin-angiotensin mechanism regulates blood volume and pressure. When the blood pressure decreases, the kidneys release a hormone called renin, which triggers a cascade of reactions leading to the production of angiotensin II. Angiotensin II causes blood vessels to constrict, leading to an increase in blood pressure. Additionally, it triggers the adrenal glands to release aldosterone, which causes the kidneys to retain sodium and water, leading to an increase in blood volume and blood pressure.
6. Explain how ADH compensates for blood that contains too many solutes.
ADH (Anti-Diuretic Hormone) is a hormone released by the pituitary gland in response to changes in the body’s fluid balance. When blood contains too many solutes, ADH is released, causing the kidneys to reabsorb water from the urine and return it to the bloodstream. This process leads to concentrated urine and helps to reduce the solute load in the bloodstream, thereby compensating for the high solute concentration in the blood.
