Number of brain cells that become dead at the age of 70 years constitute

Options

A. `10%`
B. `20%`
C. `30%`
D. `55%`

Answer

To solve the question regarding the number of brain cells that become dead at the age of 70 years, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Aging and Brain Cells**:
- As individuals age, particularly around the age of 70, they experience various signs of aging, including the senescence (aging) of cells. This process affects brain cells as well.

2. **Impact of Aging on Brain Cells**:
- Aging leads to a decline in overall body metabolism and brain function. One significant change is the deterioration of white matter in the brain, which is crucial for efficient communication between brain cells.

3. **Deterioration of Myelin Sheath**:
- The myelin sheath, which insulates nerve fibers and facilitates the transmission of electrical signals in the brain, begins to deteriorate after the age of 40. By the time a person reaches 70, this deterioration is more pronounced.

4. **Consequences of Brain Cell Death**:
- The decline in brain cell health can lead to memory loss and cognitive decline. This may manifest as short-term memory loss and can progress to more severe conditions like dementia or other neurological disorders.

5. **Quantifying Brain Cell Death**:
- Research and studies indicate that approximately 20% of brain cells may die by the age of 70 due to the aging process and associated neurological issues.

6. **Selecting the Correct Option**:
- Given the options provided (10%, 20%, 30%, 55%), the correct answer is that at the age of 70, approximately **20%** of brain cells become dead.

### Final Answer:
The number of brain cells that become dead at the age of 70 years constitutes **20%**.

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