Describe the mechanism by which normal fluid regulation in the body occurs. What

Question

Describe the mechanism by which normal fluid regulation in the body occurs. What is considered to be excessive thirst and urination in an adult? List and briefly describe the four types of diabetes insipidus. How is pituitary diabetes insipidus diagnosed? In what ways is diabetes insipidus similar to diabetes mellitus? In what ways do they differ? How does the mechanism by which diuresis occurs with diabetes insipidus differ from that which occurs in diabetes mellitus? How does diabetes insipidus compare with a condition called syndrome of inappropriate anti-diuretic hormone (SIADH)? What other conditions result in polyuria and polydipsia (PU/PD)? What is DDAVP and how is it administered? Why should a person who has pituitary diabetes insipidus and does not feel unreasonably inconvenienced by the symptoms take treatment? Why is ADH also known as vasopressin?

Explanation / Answer

Answer 1)

The fluid regulation in the body means to balance the water in the body. Body losses water through urine, perspiration, respiration, defecation and expectoration. The need of water (dehydration condition) is fulfilled through thirst mechanism by the body. Body will try to release as little water as possible through urine, which is stored in the bladder. To secrete the extra water (over-hydration) a hormone called Anti-diuretic hormone (ADH) also called vasopressin is required. This hormone is synthesized in the neurons with supraoptic nuclie in hypothalamus. They are transported to the posterior pituitary. The sensory nerves will sense the presence of excess water in the body i.e. it will sense the osmolarity of the cells. It will excite the neurons of supraoptic nucleus and which in turns activate the action potential to posterior pituitary and ADH is secreted. ADH is released in the blood which will increase the cell permeability and take up the excess of water to maintain the osmolarity of plasma.

Answer 2)

In normal condition body generally passes 1 – 2 quarts of urine in a day. During diabetes insipidus, body can pass urine from 3 to 20 quarts in a day. Also when body takes up of 4 quarts of water in a day, it is considered excess thirst.

Answer 3)

Type of Diabetes insipidus:

Answer 4)

MRI is used to diagnose pituitary diabetes insipidus. The MRI doesnot directly diagnose the insipidus, instead it shows if there is any problem in the hypothalamus or pituitary gland of the body.

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