lncrease in the excitability of nerves and muscles leading to sustained contraction of the muscles of larynx, face, hand and feet is due to

Options

A. Hyper activity of thyroid
B. Hyper activity of parathyroid
C. Hypoactivity of thyroid
D. Hypoactivity of parathyroid

Answer

To solve the question regarding the increase in the excitability of nerves and muscles leading to sustained contraction of the muscles of the larynx, face, hand, and feet, we need to analyze the roles of the thyroid and parathyroid glands and their hormones.

### Step-by-Step Solution:

1. **Understanding the Glands**:
- The thyroid gland produces hormones such as thyroxine (T4) which regulates metabolism, while the parathyroid glands produce parathyroid hormone (PTH) which regulates calcium levels in the blood.

2. **Hyperactivity vs. Hypoactivity**:
- Hyperactivity of a gland means that it is producing excessive amounts of hormones, while hypoactivity means it is producing insufficient amounts.

3. **Effects of Hyperthyroidism**:
- In hyperthyroidism (hyperactivity of the thyroid), there is an excess of thyroxine, which can lead to symptoms like weight loss and increased heart rate, but it does not specifically lead to increased excitability of nerves and muscles.

4. **Effects of Hypothyroidism**:
- In hypothyroidism (hypoactivity of the thyroid), there is a deficiency of thyroxine, which can lead to symptoms like fatigue and weight gain, but again, it does not directly cause increased excitability.

5. **Effects of Hyperparathyroidism**:
- In hyperparathyroidism (hyperactivity of the parathyroid), there is an increase in parathyroid hormone which raises calcium levels in the blood. High calcium levels can lead to increased excitability of nerves and muscles, resulting in sustained contractions and spasms.

6. **Effects of Hypoparathyroidism**:
- In hypoparathyroidism (hypoactivity of the parathyroid), there is a decrease in parathyroid hormone, leading to low calcium levels. This can also increase excitability but typically results in symptoms like muscle cramps and spasms due to low calcium.

7. **Conclusion**:
- The sustained contraction of muscles in the larynx, face, hands, and feet is primarily due to hyperactivity of the parathyroid gland, which increases calcium levels and enhances the excitability of nerves and muscles.

### Final Answer:
The increase in the excitability of nerves and muscles leading to sustained contraction of the muscles of the larynx, face, hand, and feet is due to **hyperactivity of the parathyroid gland**.

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