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Ch. 26 The Urinary System
Martini - Fundamentals of Anatomy & Physiology 11th Edition
Martini, Nath, Bartholomew11th EditionFundamentals of Anatomy & PhysiologyISBN: 9780136874089당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Martini, Nath, Bartholomew 11th EditionCh. 26 The Urinary System문제 16
25장, 문제 16

When the renal threshold for a substance exceeds its tubular maximum:
(a) More of the substance will be filtered
(b) More of the substance will be reabsorbed
(c) More of the substance will be secreted
(d) The amount of the substance that exceeds the tubular maximum will be found in the urine
(e) Both a and d occur

검증된 단계별 안내
1
Step 1: Understand the key terms involved in the problem. The 'renal threshold' is the plasma concentration level at which a substance begins to appear in the urine because the kidneys cannot reabsorb it all. The 'tubular maximum' (Tm) is the maximum rate at which the renal tubules can reabsorb a substance.
Step 2: Recognize that when the plasma concentration of a substance exceeds the renal threshold, the filtered load of that substance surpasses the tubular maximum reabsorption capacity.
Step 3: Since the tubular maximum is exceeded, the tubules cannot reabsorb all of the filtered substance, so the excess amount remains in the tubular fluid and is excreted in the urine.
Step 4: Analyze the answer choices in this context: (a) More of the substance will be filtered — filtration depends on plasma concentration and glomerular filtration rate, so if plasma concentration increases, filtered load increases; (d) The amount exceeding the tubular maximum will appear in urine because it cannot be reabsorbed.
Step 5: Conclude that the correct understanding is that both more of the substance is filtered (due to higher plasma concentration) and the excess beyond the tubular maximum appears in urine, which corresponds to answer (e).

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Renal Threshold

The renal threshold is the plasma concentration level of a substance at which the kidneys begin to excrete it into the urine because reabsorption mechanisms are saturated. Below this threshold, the substance is mostly reabsorbed; above it, excess amounts appear in urine.
추천 영상:
4:35
Transport Maximum (TM) & Renal Threshold

Tubular Maximum (Tm)

Tubular maximum refers to the highest rate at which a substance can be reabsorbed or secreted by the renal tubules. When the filtered load exceeds this maximum, the excess substance cannot be reabsorbed and is excreted in urine.
추천 영상:
4:35
Transport Maximum (TM) & Renal Threshold

Relationship Between Renal Threshold and Tubular Maximum

If the renal threshold exceeds the tubular maximum, it means the plasma concentration is high enough that the filtered load surpasses the reabsorption capacity. Consequently, the surplus substance appears in urine, indicating saturation of reabsorption.
추천 영상:
4:35
Transport Maximum (TM) & Renal Threshold
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Sympathetic activation of nerve fibers in the nephron causes 

(a) the regulation of glomerular blood flow and pressure, 

(b) the stimulation of renin release from the juxtaglomerular complex, 

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(d) all of these.

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When ADH levels rise, 

(a) The amount of water reabsorbed increases.

(b) The DCT becomes impermeable to water.

(c) The amount of water reabsorbed decreases.

(d) Sodium ions are exchanged for potassium ions.

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(a) ADH

(b) Renin

(c) Aldosterone

(d) Erythropoietin

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