What conditions are responsible for stimulation of juxtaglomerular apparatus

Options

A. An increase in blood pressure or blood volume in heart
B. An increase in the solute concentration of the blood plasma
C. A decrease in the solute concentration of the blood plasma
D. Decrease in blood pressure or blood volume in afferent arteriole

Answer

### Step-by-Step Solution:

1. **Understanding the Juxtaglomerular Apparatus (JGA)**:
- The JGA is a specialized structure formed by the modification of cells in the afferent arteriole and the distal convoluted tubule (DCT) of the nephron.
- Its primary function is to regulate kidney function, particularly blood pressure and blood volume.

2. **Mechanism of Stimulation**:
- The JGA is stimulated under specific conditions, particularly when there is a decrease in blood pressure (BP) or blood volume.
- This decrease can occur due to various reasons such as trauma, blood loss, diarrhea, or vomiting.

3. **Renin Secretion**:
- In response to low BP or blood volume, the JGA secretes an enzyme called renin.
- Renin plays a crucial role in the renin-angiotensin-aldosterone system (RAAS).

4. **Conversion of Angiotensinogen**:
- Renin converts angiotensinogen (a protein produced by the liver) into angiotensin I.
- Angiotensin I is then converted into angiotensin II by the action of the enzyme angiotensin-converting enzyme (ACE).

5. **Effects of Angiotensin II**:
- Angiotensin II has multiple effects:
- It stimulates the adrenal cortex to release aldosterone.
- Aldosterone increases the reabsorption of sodium and water in the kidneys, which helps restore blood volume and pressure.
- Angiotensin II is also a potent vasoconstrictor, narrowing blood vessels and further increasing blood pressure.

6. **Conclusion**:
- The primary conditions that stimulate the juxtaglomerular apparatus are a decrease in blood pressure and blood volume.

### Final Answer:
The conditions responsible for the stimulation of the juxtaglomerular apparatus are a decrease in blood pressure and blood volume.

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