# 25.9 Regulation of fluid volume and composition  (Page 3/9)

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## Regulation of cl –

Chloride is important in acid–base balance in the extracellular space and has other functions, such as in the stomach, where it combines with hydrogen ions in the stomach lumen to form hydrochloric acid, aiding digestion. Its close association with Na + in the extracellular environment makes it the dominant anion of this compartment, and its regulation closely mirrors that of Na + .

## Regulation of ca ++ And phosphate

The parathyroid glands monitor and respond to circulating levels of Ca ++ in the blood. When levels drop too low, PTH is released to stimulate the DCT to reabsorb Ca ++ from the forming urine. When levels are adequate or high, less PTH is released and more Ca ++ remains in the forming urine to be lost. Phosphate levels move in the opposite direction. When Ca ++ levels are low, PTH inhibits reabsorption of ${\text{HPO}}_{4}^{2-}$ so that its blood level drops, allowing Ca ++ levels to rise. PTH also stimulates the renal conversion of calcidiol into calcitriol, the active form of vitamin D. Calcitriol then stimulates the intestines to absorb more Ca ++ from the diet.

## Regulation of h + , bicarbonate, and ph

The acid–base homeostasis of the body is a function of chemical buffers and physiologic buffering provided by the lungs and kidneys. Buffers, especially proteins, ${\text{HCO}}_{3}^{2-}$ , and ammonia have a very large capacity to absorb or release H + as needed to resist a change in pH. They can act within fractions of a second. The lungs can rid the body of excess acid very rapidly (seconds to minutes) through the conversion of HCO 3 into CO 2 , which is then exhaled. It is rapid but has limited capacity in the face of a significant acid challenge. The kidneys can rid the body of both acid and base. The renal capacity is large but slow (minutes to hours). The cells of the PCT actively secrete H + into the forming urine as Na + is reabsorbed. The body rids itself of excess H + and raises blood pH. In the collecting ducts, the apical surfaces of intercalated cells have proton pumps that actively secrete H + into the luminal, forming urine to remove it from the body.

As hydrogen ions are pumped into the forming urine, it is buffered by bicarbonate (HCO 3 ), H 2 PO 4 (dihydrogen phosphate ion), or ammonia (forming NH 4 + , ammonium ion). Urine pH typically varies in a normal range from 4.5 to 8.0.

## Regulation of nitrogen wastes

Nitrogen wastes are produced by the breakdown of proteins during normal metabolism. Proteins are broken down into amino acids, which in turn are deaminated by having their nitrogen groups removed. Deamination converts the amino (NH 2 ) groups into ammonia (NH 3 ), ammonium ion (NH 4 + ), urea, or uric acid ( [link] ). Ammonia is extremely toxic, so most of it is very rapidly converted into urea in the liver. Human urinary wastes typically contain primarily urea with small amounts of ammonium and very little uric acid.

## Elimination of drugs and hormones

Water-soluble drugs may be excreted in the urine and are influenced by one or all of the following processes: glomerular filtration, tubular secretion, or tubular reabsorption. Drugs that are structurally small can be filtered by the glomerulus with the filtrate. Large drug molecules such as heparin or those that are bound to plasma proteins cannot be filtered and are not readily eliminated. Some drugs can be eliminated by carrier proteins that enable secretion of the drug into the tubule lumen. There are specific carriers that eliminate basic (such as dopamine or histamine) or acidic drugs (such as penicillin or indomethacin). As is the case with other substances, drugs may be both filtered and reabsorbed passively along a concentration gradient.

## Chapter review

The major hormones regulating body fluids are ADH, aldosterone and ANH. Progesterone is similar in structure to aldosterone and can bind to and weakly stimulate aldosterone receptors, providing a similar but diminished response. Blood pressure is a reflection of blood volume and is monitored by baroreceptors in the aortic arch and carotid sinuses. When blood pressure increases, more action potentials are sent to the central nervous system, resulting in greater vasodilation, greater GFR, and more water lost in the urine. ANH is released by the cardiomyocytes when blood pressure increases, causing Na + and water loss. ADH at high levels causes vasoconstriction in addition to its action on the collecting ducts to recover more water. Diuretics increase urine volume. Mechanisms for controlling Na + concentration in the blood include the renin–angiotensin–aldosterone system and ADH. When Na + is retained, K + is excreted; when Na + is lost, K + is retained. When circulating Ca ++ decreases, PTH stimulates the reabsorption of Ca ++ and inhibits reabsorption of ${\text{HPO}}_{4}^{2-}$ . pH is regulated through buffers, expiration of CO 2 , and excretion of acid or base by the kidneys. The breakdown of amino acids produces ammonia. Most ammonia is converted into less-toxic urea in the liver and excreted in the urine. Regulation of drugs is by glomerular filtration, tubular secretion, and tubular reabsorption.

What is red blood cell
A type of blood cell that is made in the bone marrow and found in the blood. Red blood cells contain a protein called hemoglobin, which carries oxygen from the lungs to all parts of the body. Checking the number of red blood cells in the blood is usually part of a complete blood cell (CBC) test. It
Noor
red blood cell are the most numerous blood cells.they comprise about 99% of all blood cells red blood cells are non nucleated it has red colour due to present to hemoglobin.
Vineeta
HANNAH
how will you promote quality of life in ptb patient using the 14 basic needs and 21 nursing problems?
coronary circulation ?
Coronary circulation is the circulation of blood in the blood vessels that supply the heart muscle (myocardium). Coronary arteries supply oxygenated blood to the heart muscle, and cardiac veins drain away the blood once it has been deoxygenated. Because the rest of the body.
Riyaz
coronary circulation ,is flow of blood that supplies the heart tissue itself is the coronary circulation. the functional blood supply of the heart,is the shortest circulation in tha body.
Vineeta
what about the easy way to understand action potential
Bright
event of cardiac cycle
hii
Chandan
whatisanatom
anatomy is the scientific way of studying the body structure.
cynthia
the branch of science concerned with the bodily structure of humans, animals, and other living organisms, especially as revealed by dissection and the separation of parts.
Noor
what is means by LAPE and HAPE
Noor
guys i've question what occur when homeostasis balance mechanisms lost
Bladder is blank to the small intestine, what is the right directional term for that?
When peristaltic movement is correct.
Farid
what tissue that support body organ?
the skeleton
veronica
Skeleton
GEBAH
skeleton
Juwita
skeleton
Farid
skeleton
Priya
skeleton
Emmanuel
skeleton
Noor
skeleton
BILAL
skeleton
hanuman
how many bones are there in the body
go uuu
206
206
Nelago
206
Esmeralda
206
Joey
baby me 360. and human body 206.found bones.....
Sneha
what is a tissue in Anatomy and physiology
Nelago
206 bones
Juwita
what is an example of a molecule that can directly pass through the phospholipid bilayer of the plasma membrane?
Kathy
206
Johara
how many bones are there in the hand and wrist
hanuman
200 tissue
hanuman
GEBAH
axial 80 appendicular 126 total bone is 206
Vineeta
wrist bone 8
Vineeta
baby bone 270 he is correct answer
hanuman
Jo carpus wrist bone h
Vineeta
206
Musonda
206 bones in human body.
Farid
What is Heart attack?
Farid
206
Priti
206 all
Sa
All 206
Sa
A heart attack happens when the flow of oxygen-rich blood to a section of heart muscle suddenly becomes blocked and the heart can't get oxygen. If blood flow isn't restored quickly, the section of heart muscle begins to die. Heart attack treatment works best when it's given right after symptoms occu
Riyaz
how can l understand Anatomy quickly?
you can't!!!! Anatomy is easy but the physiology takes time to understand. Anatomy is simply systems and organs but you must take time to learn physiology to understand how the anatomy works
Rachael
alright.. so how can l at least memorize the information about physiology?
Agness
what name is given to the fluid that is drawn from the villi to the lymphatic vessels
I think venous
Noor
lymph
Rachael
I also think it's lymph
Akhi
me too I think lymph
Esmeralda
ans Rhythmic contraction
GEBAH
what are the ten (10) rights for drug administration
GEBAH
importance of muscle in the anatomical structures.
it permits the constant level of movement,and gives structure and shape to the body
Priya
what is assimilation
cellular level organism level chemical level organ system level tissue level organ level
, the current topic
Hilya
cellular level
Priya
tissue level
Priya
organ level
Priya
organ systems level
Priya
organism level
Priya
what is anatomy?
anatomy is the study of internal parts of body by disecting it.
Shweta
The study of the internal body parts and it's organs are referred as Anatomy.