Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

25. The Urinary System

Renal Physiology Step 2: Tubular Reabsorption

Anatomy & Physiology

25. The Urinary System

Renal Physiology Step 2: Tubular Reabsorption

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1:58 minutes

Problem 27

Textbook Question

Two physiology students are having a disagreement about renal function. Dan says that the kidneys work harder when you eat a high-salt diet, whereas Peter says that they work harder when you drink lots of water. Who is right, and why?

Verified step by step guidance

Step 1: Begin by understanding the primary functions of the kidneys. The kidneys are responsible for filtering blood, maintaining electrolyte balance, regulating fluid levels, and excreting waste products through urine. They adjust their workload based on the body's needs.

Step 2: Analyze Dan's claim about a high-salt diet. A high-salt diet increases the concentration of sodium in the blood. The kidneys respond by filtering out excess sodium to maintain homeostasis. This process involves increased reabsorption and excretion mechanisms, which can place additional workload on the kidneys.

Step 3: Examine Peter's claim about drinking lots of water. When you consume large amounts of water, the kidneys work to maintain fluid balance by excreting the excess water as dilute urine. This process involves adjusting the concentration of urine through mechanisms like reduced reabsorption of water in the nephron.

Step 4: Compare the two scenarios. Both high-salt intake and excessive water consumption require the kidneys to adjust their filtration and excretion processes. However, the type of workload differs: high-salt intake primarily affects electrolyte regulation, while excessive water intake primarily affects fluid balance.

Step 5: Conclude that both Dan and Peter are correct in their own contexts. The kidneys work harder in both scenarios, but the specific mechanisms and physiological processes involved differ based on whether the challenge is related to salt or water intake.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Renal Physiology

Renal physiology is the study of kidney function and the processes involved in filtering blood, regulating electrolytes, and maintaining fluid balance. The kidneys play a crucial role in homeostasis by adjusting the volume and composition of body fluids, which is influenced by dietary intake, such as salt and water.

Osmoregulation

Osmoregulation refers to the process by which the body maintains the balance of water and electrolytes in the blood. When consuming a high-salt diet, the kidneys must excrete excess sodium while retaining water to prevent dehydration, whereas drinking lots of water requires the kidneys to excrete the surplus to maintain osmotic balance.

Glomerular Filtration Rate (GFR)

Glomerular filtration rate (GFR) is a measure of how well the kidneys filter blood, indicating renal function. GFR can be affected by fluid intake; high water consumption can increase GFR, leading to more urine production, while a high-salt diet can lead to increased workload on the kidneys to excrete excess sodium and maintain fluid balance.

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Textbook Question

Describe what is involved in active and passive tubular reabsorption.

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Textbook Question

Tubular reabsorption

a. Of glucose and many other substances is a T_m- limited active transport process

b. Of chloride is always linked to the passive transport of Na⁺

c. Is the movement of substances from the blood into the nephron

d. Of sodium occurs only in the proximal tubule

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Textbook Question

Glucose is not normally found in the urine because it

a. Does not pass through the walls of the glomerulus

b. Is kept in the blood by colloid osmotic pressure

c. Is reabsorbed by the tubule cells

d. Is removed by the body cells before the blood reaches the kidney

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Textbook Question

Which is reabsorbed by the proximal convoluted tubule cells?

a. Na⁺

b. K⁺

c. Amino acids

d. All of the above

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Textbook Question

Trace the pathway a uric acid molecule takes from a glomerulus to the urethra. Name every gross or microscopic structure it passes through on its journey.

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Textbook Question

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

a. Sodium ions and glucose are cotransported into the proximal tubule cell by secondary active transport.

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Textbook Question

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

b. The distal tubule reabsorbs sodium ions and secretes potassium and hydrogen ions in response to ADH.

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