Medical Physiology Chapter 5 & 36 Quiz

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Questions and Answers

What is the primary role of glucose-6-phosphatase (G-6-P) in the liver?

Regulation of blood glucose levels

Synthesis of amino acids

Catalyzing the breakdown of glycogen (correct)

Conversion of lactate into glucose

Which organ contributes the most to gluconeogenesis?

Kidney

Pancreas

Intestine

Liver (correct)

What happens to plasma glucose concentrations in uncontrolled Diabetes?

They decrease significantly

They are effectively filtered and reabsorbed

They exceed renal reabsorption capacity (correct)

They remain constant

Which SGLT transporter has a high affinity and low transport capacity?

SGLT1 Signup and view all the answers

What percentage of renal glucose reabsorption is attributed to SGLT2?

90% Signup and view all the answers

How does the glucose filtration rate change in response to plasma glucose concentration?

It increases with higher concentrations Signup and view all the answers

Which of the following is a common symptom of glucosuria?

Increased thirst Signup and view all the answers

What is primarily absorbed by SGLT1 in the intestines?

Galactose and glucose Signup and view all the answers

In the kidneys, what is the location of SGLT2?

Early proximal tubule (S1) Signup and view all the answers

What effect does glucosuria have on urine volume?

Increases urine volume Signup and view all the answers

What is the primary function of the renal system?

Maintaining proper osmolarity of body fluids Signup and view all the answers

What percentage of plasma is filtered through the renal corpuscle during glomerular filtration?

20% Signup and view all the answers

How is glucose primarily reabsorbed in the kidneys?

Via Sodium Glucose co-Transporters (SGLTs) Signup and view all the answers

What is the glomerular filtration rate (GFR) at which blood is filtered in the kidneys?

125 mL min-1 Signup and view all the answers

Which process involves the conversion of non-carbohydrate sources into glucose in the kidney?

Gluconeogenesis Signup and view all the answers

What role do the kidneys play in maintaining glucose homeostasis?

They reabsorb glucose and release it based on metabolic needs. Signup and view all the answers

Which of the following ions is NOT regulated by the renal system?

Iron (Fe) Signup and view all the answers

What happens during tubular secretion in the renal process?

Organic acids and bases are secreted into the urine. Signup and view all the answers

What is the primary role of erythropoietin produced by the kidneys?

Stimulate red blood cell production Signup and view all the answers

Which of the following statements about the renal system is FALSE?

The kidneys exclusively excrete all types of metabolites. Signup and view all the answers

Study Notes

Renal Function and Glucose Homeostasis

The renal system consists of paired kidneys, ureters, a bladder, and a urethra. Its primary function is filtration, secretion, and reabsorption.
Kidneys maintain water balance, proper osmolarity of body fluids, and regulate ions in extracellular fluid (ECF).
Key functions also include maintaining plasma volume, acid-base balance, excretion of bodily metabolic products and foreign compounds, erythropoietin production, renin production, vitamin D conversion, and glucose homeostasis.
Kidneys filter the entire plasma volume (~3 liters) approximately 60 times daily.

Learning Outcomes

Demonstrate the function of the renal system in homeostasis.
Demonstrate the role of the kidneys in glucose handling.
Describe how renal glucose reabsorption is quantified.

Renal Processes

Glomerular filtration: Protein-free plasma (20%) is filtered through the renal corpuscle (Bowman capsule and glomerulus) at a rate of 125 mL/min (glomerular filtration rate (GFR)).
Tubular reabsorption: Valuable substances like glucose are reabsorbed in the renal tubules.
Tubular secretion: Organic acids and bases are secreted into the urine in the proximal convoluted tubule.

Renal Glucose Handling

Glucose reabsorption occurs through Sodium Glucose coTransporters (SGLTs).
Glucose release into circulation happens via gluconeogenesis.
Glucose is taken up from circulation to meet energy demands.

Gluconeogenesis in the Kidney

Gluconeogenesis synthesizes new glucose from non-carbohydrate sources (lactate, amino acids, glycerol).
It is mediated by glucose-6-phosphatase (G-6-P).
Primarily occurs in the liver, but kidneys contribute (20-25% of gluconeogenesis).

Filtration Rate of Glucose

All plasma glucose is filtered by the kidneys.
Glucose filtration rate reflects the amount of glucose filtered.
Glucose filtration is directly proportional to plasma glucose concentration. A higher plasma glucose concentration leads to a higher filtration rate.

Glucose Titration Studies

Glucose is a critical biochemical fuel for neurons and retina.
Renal glucose filtering must be balanced by reabsorption.
Renal glucose handling can be measured clinically through glucose titration studies.
In uncontrolled diabetes, plasma glucose levels exceeding reabsorption capacity lead to glucosuria (glucose in urine), polyuria (increased urine volume), and polydipsia (increased thirst).

Glucose Reabsorption by SGLTs

Six members (1, 2, 4, 5, 6, and SMIT1) of the SGLT family reabsorb glucose.
SGLT1 is predominantly located in the intestine and late proximal tubule (S3), with high glucose affinity (Km = 0.4 mM).
SGLT2 is primarily in the early proximal tubule (S1), with lower affinity (km = 2 mm), but reabsorbs 90% of glucose.
SGLT2 inhibitors are used in treating type 2 diabetes (e.g., canagliflozin, dapagliflozin, empagliflozin, ertugliflozin). These inhibitors reduce glucose reabsorption, leading to glucosuria and lower blood glucose.

Summary

Kidney's role in glucose homeostasis involves glucose reabsorption, gluconeogenesis, and glucose uptake.
SGLT2 inhibitors exploit the kidney's role in glucose reabsorption to lower blood glucose in type 2 diabetes.

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Description

Test your understanding of renal function and its role in glucose homeostasis with this quiz based on Medical Physiology. Explore the intricate processes of filtration, secretion, and regulation performed by the kidneys. You'll assess your knowledge on how these functions contribute to overall homeostasis and glucose management.