Problem 147 - Objective Biology for NEET

Question

Assertion: PTH increases the \(\mathrm{Ca}^{2+}\) level in blood Reason: PTH stimulates the process of bone resorption.

Step-by-Step Solution

Answer

Yes, PTH does increase the \(\mathrm{Ca}^{2+}\) level in blood as it stimulates bone resorption, a process which releases calcium ions from bone tissue into the blood.

Step 1: Understand the role of PTH

The parathyroid hormone (PTH) is a type of hormone secreted by the parathyroid glands. It plays a critical role in regulating blood calcium levels by maintaining the balance between calcium and phosphate.

Step 2: Explain Bone resorption

Bone resorption is a process by which osteoclasts break down the tissue in bones and release the minerals, resulting in the transfer of calcium from bone tissue to blood.

Step 3: Connect Bone resorption with Blood calcium level

During the above process, as bone resorption takes place, the released minerals that include calcium ions (\(\mathrm{Ca}^{2+}\)) will enter the bloodstream, thereby increasing calcium levels in the blood.

Key Concepts

Bone Resorption

Bone resorption is a vital physiological process that helps maintain the balance of minerals, particularly calcium, in our bodies. In simpler terms, it's the process by which bones are broken down, releasing essential minerals into the bloodstream. This process is crucial not only for the regulation of calcium but also for bone health and growth.

Let's break it down further. During bone resorption, specialized cells called osteoclasts attach to the bone surface. They secrete acids and enzymes that dissolve the bone mineral matrix, freeing up minerals like calcium and phosphate. This action serves two main purposes:

• It helps regulate the levels of calcium in the blood, ensuring that our body's calcium-dependent functions—such as muscle contraction and nerve transmission—occur smoothly.
• It prepares for bone remodeling, an essential part of maintaining bone strength and facilitating growth.

Overall, bone resorption is more than just breaking down bone. It's about providing minerals to the bloodstream, helping with various physiological needs.

Calcium Regulation

Calcium regulation is crucial for maintaining various body functions. Since calcium is needed for muscle contraction, blood coagulation, and nerve impulse transmission, its levels in the blood have to be tightly controlled.

The parathyroid hormone (PTH) plays a major role in this regulatory process. When blood calcium levels drop below normal, the parathyroid glands secrete PTH. This hormone catalyzes actions in the body to restore calcium levels, including:

• Stimulating bone resorption, which increases the release of calcium from the bones into the bloodstream.
• Enhancing the kidney's ability to retain calcium, reducing calcium excretion through urine.
• Promoting activation of vitamin D, which increases calcium absorption from the intestine.

Through these pathways, PTH ensures that our calcium levels remain within a stable range, supporting various vital processes.

Osteoclasts

Osteoclasts are the cells at the heart of bone resorption. Imagine them as diligent workers breaking down old buildings to recycle materials for future construction. These cells are large, multi-nucleated, and arise from the fusion of multiple precursor cells.

The activity of osteoclasts is stimulated by the parathyroid hormone (PTH) when blood calcium levels are low. Osteoclasts bind to the bone matrix and release enzymes and acids that dissolve bone tissue. This action releases calcium ions into the bloodstream, thus aiding in the regulation of calcium levels.

With their specific function, osteoclasts play a part in both bone maintenance and calcium regulation. They

• Ensure bones are remodeled properly, which is essential for health and growth.
• Help regulate calcium levels, integral for the body’s overall calcium homeostasis.

This dual role makes osteoclasts essential for both bone health and metabolic balance.