Question

1. Why would the body closely regulate blood calcium levels? Your answer should include four reasons.

2.  Explain the role of the hormone calcitonin. Include the following in your response.

• What triggers the hormone

• The source of the hormone, where does it come from

• The specific action(s) of the hormone

• When is this hormone most active, what part of the lifecycle and why is this?

Answer 1

Ans1:- normal Calcium concentration in plasma is 9.4mg/dl.it has to need closely regulate itit. extreme hypocalcemia can cause effects in patients, such as marked dilation of the heart, changes in cellular enzyme activities, increased membrane permeability in some cells (in addition to nerve cells), and impaired blood clotting.

Hypocalcemia also Causes Nervous System Excitement and Tetany. When the extracellular fluid concentration of calcium ions falls below normal, the nervous system becomes progressively more excitable because this phe nomenon causes increased neuronal membrane permeability to sodium ions, allowing easy initiation of action potentials. andand initia trains of nerve impulses that pass to the peripheral skeletal muscles to elicit tetanic muscle contraction. Consequently, hypocalcemia causes tetany. It also occasionally causes seizures because of its action of increasing excitability in the brain. This is called carpopedal spasm. Tetany ordinarily occurs when the blood concentra tion of calcium falls from its normal level of 9.4 mg/dl to about 6 mg/dl.

Hypercalcemia Depresses Nervous System and Muscle Activity. When the level of calcium in the body fluids rises above normal, the nervous system becomes depressed and reflex activities of the central nervous system are sluggish. Also, increased calcium ion concentration decreases the QT interval of the heart and causes lack of appetite and constipation, probably because of depressed contractility of the muscle walls of the gastrointestinal tract.

Ans2:- SOURCE OF THE CALCITONINC:-ALCITONIN is secreted by the parafollicular cells or clear cells, situated in the follicles in thyroid gland.

TRIGGERS OF CALCITONIN:- Plasma Calcium Concentration Stimulates Calcitonin Secretion. The primary stimulus for calcitonin secretion is increased extracellular fluid calcium ion concentration.an increase in plasma calcium concentration of about 9.5mg/dl causes an immediate increase in the rate of secretion of calcitonin.

beta aderneragic agonists estrogen,dopamine,glucagon ,cck stimulates Calcitonin secretion.

ACTION:-receptors for calciCalci action are found inthe bones and kidney,due to which it causes lowers circulating Calcium level by inhibiting bone resorption and calcitonin inhbits the action of osteoclasts.

EFFECT OF CALCITONIN IS MUCH GREATER IN CHILDREN RATHER THAN ADULTS.

The effect of calcitonin in children is much greater because bone remodeling occurs rapidly in children, with absorption and deposition of calcium as great as 5 grams or more per day.