Homeostasis A: Water Balance and Body Fluids

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Questions and Answers

What is the critical value at which the pH of the extracellular fluid must be maintained?

7.0

7.4 (correct)

7.2

7.8

Which symptom would most likely indicate dehydration in a 9-month-old child?

Sunken anterior fontanel (correct)

Elevated blood pressure

Increased respiratory rate

Excessive urination

What fluid balance alteration is indicated by hypernatremia?

Low potassium concentration

Normal sodium concentration

Low sodium concentration

High sodium concentration (correct)

What type of solution was used to treat the 86-year-old man with hypernatremia?

5% glucose in saline solution Signup and view all the answers

How does body temperature relate to homeostasis?

It must be maintained at 37.5°C. Signup and view all the answers

What condition can result from inadequate water and electrolyte balance?

Dehydration Signup and view all the answers

In the context of homeostasis, what does the term physiological limits refer to?

The boundaries within which the body can function optimally Signup and view all the answers

Why are feedback signals crucial in homeostatic mechanisms?

They ensure maintenance of the internal environment. Signup and view all the answers

What is the minimum urine output required to maintain neutral solute balance?

500 mL/day Signup and view all the answers

What occurs if someone does not produce at least 500 mL of urine daily?

They will have renal failure Signup and view all the answers

What is the term for the amount of water loss that is considered obligatory?

Obligate water loss Signup and view all the answers

What substances may build up in the body during renal failure due to inadequate urine output?

Sodium, potassium, and urea Signup and view all the answers

Which factor does NOT influence the distribution of body fluids?

Diet Signup and view all the answers

Which of the following best describes 'obligate water loss'?

The minimum volume of urine output required Signup and view all the answers

Which value represents the osmolarity levels related to water release in mOsmol?

600 mOsmol Signup and view all the answers

What is likely to happen if someone experiences excessive water retention?

Reduced kidney function Signup and view all the answers

What is the estimated percentage of body weight that water accounts for in men?

60% Signup and view all the answers

Why do women generally have less body water compared to men?

They have more body fat. Signup and view all the answers

What is the body water percentage for women according to the 60-40-20 rule?

50% Signup and view all the answers

Based on the provided information, what is the significant relationship described between plasma and interstitial fluid?

They exchange water. Signup and view all the answers

If men weigh 70 kg, how much of that weight is accounted for by water?

42 kg Signup and view all the answers

How is body fat related to the amount of water a person has?

More body fat means less water. Signup and view all the answers

What is the total volume of interstitial fluid if 50% of GORg is 30L?

30L Signup and view all the answers

What is an implication of the 60-40-20 rule for athletes?

Hydration status is crucial for body weight management. Signup and view all the answers

What does osmolarity measure in a solution?

Concentration of solutes in the solution Signup and view all the answers

What direction does water move in relation to solute concentration?

From low solute concentration to high solute concentration Signup and view all the answers

When does water stop moving between different concentrations of solute?

When equilibrium is found Signup and view all the answers

Which statement is true regarding osmolarity?

Osmolarity is expressed as concentration Signup and view all the answers

What happens to solute concentration when water moves freely between two solutions?

Both concentrations equalize Signup and view all the answers

What role do aquaporins play in cells?

They create pores for water movement. Signup and view all the answers

How does water primarily move across cellular membranes?

Through diffusion and specialized channels. Signup and view all the answers

What regulates the thirst mechanisms in the body?

The hypothalamus. Signup and view all the answers

What is the primary factor that maintains total body water balance?

Equilibrium between water intake and excretion. Signup and view all the answers

Which process is involved in the passive movement of water?

Facilitated diffusion. Signup and view all the answers

What happens to water molecules that slip between adjacent membrane phospholipid molecules?

They contribute to cellular edema. Signup and view all the answers

What is the function of ion channels in water movement?

They allow water to move along with solutes. Signup and view all the answers

Which of the following is NOT a method by which cells can regulate water movement?

Endocytosis of extracellular fluid. Signup and view all the answers

Study Notes

Homeostasis and Water Balance

Homeostasis maintains the internal environment within physiological limits, crucial for survival.
Blood pH must be kept around 7.4, and body temperature should be maintained at approximately 37.5°C.
Nutrient and oxygen supply to cells is essential for proper metabolism.
Homeostatic mechanisms utilize feedback signals to regulate water and electrolyte balance, aiming for optimal osmolarity.

Clinical Cases

Case 1 (9-month-old boy): Symptoms include diarrhea, vomiting, fever, tachycardia, and decreased skin turgor. Treatment involved intravenous glucose saline.
Case 2 (86-year-old man): Presented with lethargy, refusal to drink, sunken eyes, and dry mouth, indicating severe dehydration. Lab results showed hypernatremia and increased plasma osmolarity. Treated with 5% glucose in saline.

Body Fluid Compartments

Body fluid distribution varies with age, sex, and body fat percentage.
Men typically have 60% body weight as water, while women have 50%, attributed to higher body fat in women.
The "60-40-20 Rule":
- 60% of body weight is water
- Approximately 40% is intracellular fluid
- Around 20% is extracellular fluid

Urine Output and Obligatory Water Loss

Minimum urine output of 500 mL/day is critical for solute balance (termed "Obligate water loss").
Inadequate urine production can lead to renal failure, causing toxic substances like sodium and potassium to accumulate.

Osmolarity and Water Movement

Osmolarity is the concentration of a solution, affecting water movement through semi-permeable membranes.
Water moves from low to high solute concentration until equilibrium is achieved.
Cellular edema occurs when excess fluid accumulates in cells, often due to osmotic imbalances.

Regulation of Total Body Water

Balance between water intake and excretion is vital for maintaining steady-state conditions.
Hypothalamic mechanisms play a significant role in regulating thirst, influencing water intake.
Aquaporins, ion channels, and transporters are essential for water movement in and out of cells, facilitating both passive and facilitated diffusion.

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Description

This quiz focuses on the concepts of homeostasis, particularly water balance and fluid compartments within the human body. Students will explore disruptions in body fluids and their physiological implications, with emphasis on clinical cases like dehydration in young patients. Engage with the material from Year 2, Unit I to deepen your understanding of these critical concepts.