Which of the these cells release renin when GFR drops ?

Options

A. Juxtaglomerullar cells
B. Adrenal cortex
C. Adrenal medulla
D. Posterior pituitary

Answer

To solve the question, "Which of these cells release renin when GFR drops?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question is asking which specific cells are responsible for releasing renin in response to a drop in the Glomerular Filtration Rate (GFR).

2. **Define GFR**: GFR stands for Glomerular Filtration Rate, which is the amount of filtrate produced by the kidneys' glomeruli per minute. It is an important measure of kidney function.

3. **Identify the Role of Juxtaglomerular Apparatus**: The regulation of GFR is primarily controlled by the juxtaglomerular apparatus, which includes specialized cells that respond to changes in GFR.

4. **Identify the Specific Cells**: The juxtaglomerular apparatus contains juxtaglomerular cells and macula densa cells. The juxtaglomerular cells are specifically responsible for the secretion of renin.

5. **Mechanism of Renin Release**: When GFR drops, the macula densa cells detect a decrease in sodium concentration in the tubular fluid. This triggers the juxtaglomerular cells to secrete renin.

6. **Conclusion**: Based on the information, the cells that release renin when GFR drops are the **juxtaglomerular cells**.

### Final Answer:
**Juxtaglomerular cells** are the cells that release renin when GFR drops.

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