Describe the nutritional requirement of the body Flashcards
What is the role of Vitamin D in the body?
Without vitamin D, your body cannot absorb calcium
Vitamin D refers to a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and multiple other biological effects. In humans, the most important compounds in this group are vitamin D3
Vitamin D from the diet or skin synthesis is biologically inactive; enzymatic conversion (hydroxylation) in the liver and kidney is required for activation. Calcifediol is further hydroxylated by the kidneys to form calcitriol. The biologically active form of vitamin D.
Calcitriol circulates as a hormone in the blood, having a major role regulating the concentration of calcium and phosphate, and promoting the healthy growth and remodeling of bone. Calcitriol also has other effects, including some on cell growth, neuromuscular and immune functions, and reduction of inflammation.
What is the role of calcium in the body?
Normal plasma levels of calcium are between 1-2%
Calcium performs a number of basic functions in your body. Your body uses 99 percent of its calcium to keep your bones and teeth strong, thereby supporting skeletal structure and function. The rest of the calcium in your body plays key roles in cell signaling, blood clotting, muscle contraction and nerve function. Cells use calcium to activate certain enzymes, transport ions across the cellular membrane, and send and receive neurotransmitters during communication with other cells. As an electrolyte, or a particle that helps conduct electricity in the body, calcium is also one of the key players in maintaining a regular heartbeat.
Without vitamin D, your body cannot absorb calcium
Calcium is one of the body’s electrolytes, which are minerals that carry an electric charge when dissolved in body fluids such as blood, but most of the body’s calcium is uncharged.
About 99% of the body’s calcium is stored in the bones, but cells (particularly muscle cells) and blood also contain calcium. The way to overcome this is through the process of bone resorption, in which calcium is liberated into the bloodstream through the action of bone osteoclasts. The remainder of calcium is present within the extracellular and intracellular fluids.Calcium is essential for the following:
Formation of bone and teeth
Muscle contraction
Normal functioning of many enzymes
Blood clotting
Normal heart rhythm
The body precisely controls the amount of calcium in cells and blood. The body moves calcium out of bones into blood as needed to maintain a steady level of calcium in the blood. If people do not consume enough calcium, too much calcium is mobilized from the bones, weakening them. Osteoporosis can result. To maintain a normal level of calcium in blood without weakening the bones, people need to consume at least 1,000 to 1,500 milligrams of calcium a day.
The level of calcium in blood is regulated primarily by two hormones: parathyroid hormone and calcitonin.
Parathyroid hormone is produced by the four parathyroid glands, located around the thyroid gland in the neck. When the calcium level in blood decreases, the parathyroid glands produce more parathyroid hormone. When the calcium level in blood increases, the parathyroid glands produce less hormone. Parathyroid hormone does the following:
Stimulates bones to release calcium into blood
Causes the kidneys to excrete less calcium in urine
Stimulates the digestive tract to absorb more calcium
Causes the kidneys to activate vitamin D, which enables the digestive tract to absorb more calcium
Calcitonin is produced by cells of the thyroid gland. It lowers the calcium level in blood by slowing the breakdown of bone, but only slightly.
Too little calcium in the blood is called hypocalcemia; too much calcium in the blood is called hypercalcemia
In electrically excitable cells, such as skeletal and cardiac muscles and neurons, membrane depolarization leads to a Ca2+ transient with cytosolic Ca2+ concentration reaching 400 nM and above. Mitochondria are capable of sequestering and storing some of that Ca2+. It has been estimated that mitochondrial matrix free calcium concentration rises to the tens of micromolar levels in situ during neuronal activity.
