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Decreased blood volume resulting from water loss has two additional effects. First, baroreceptors, blood-pressure receptors in the arch of the aorta and the carotid arteries in the neck, detect a decrease in blood pressure that results from decreased blood volume. The heart is ultimately signaled to increase its rate and/or strength of contractions to compensate for the lowered blood pressure.

Second, the kidneys have a renin-angiotensin hormonal system that increases the production of the active form of the hormone angiotensin II, which helps stimulate thirst, but also stimulates the release of the hormone aldosterone from the adrenal glands. Aldosterone increases the reabsorption of sodium in the distal tubules of the nephrons in the kidneys, and water follows this reabsorbed sodium back into the blood.

If adequate fluids are not consumed, dehydration results and a person’s body contains too little water to function correctly. A person who repeatedly vomits or who has diarrhea may become dehydrated, and infants, because their body mass is so low, can become dangerously dehydrated very quickly. Endurance athletes such as distance runners often become dehydrated during long races. Dehydration can be a medical emergency, and a dehydrated person may lose consciousness, become comatose, or die, if his or her body is not rehydrated quickly.

Regulation of water output

Water loss from the body occurs predominantly through the renal system. A person produces an average of 1.5 liters (1.6 quarts) of urine per day. Although the volume of urine varies in response to hydration levels, there is a minimum volume of urine production required for proper bodily functions. The kidney excretes 100 to 1200 milliosmoles of solutes per day to rid the body of a variety of excess salts and other water-soluble chemical wastes, most notably creatinine, urea, and uric acid. Failure to produce the minimum volume of urine means that metabolic wastes cannot be effectively removed from the body, a situation that can impair organ function. The minimum level of urine production necessary to maintain normal function is about 0.47 liters (0.5 quarts) per day.

The kidneys also must make adjustments in the event of ingestion of too much fluid. Diuresis , which is the production of urine in excess of normal levels, begins about 30 minutes after drinking a large quantity of fluid. Diuresis reaches a peak after about 1 hour, and normal urine production is reestablished after about 3 hours.

Role of adh

Antidiuretic hormone (ADH) , also known as vasopressin, controls the amount of water reabsorbed from the collecting ducts and tubules in the kidney. This hormone is produced in the hypothalamus and is delivered to the posterior pituitary for storage and release ( [link] ). When the osmoreceptors in the hypothalamus detect an increase in the concentration of blood plasma, the hypothalamus signals the release of ADH from the posterior pituitary into the blood.

Antidiuretic hormone (adh)

This set of diagrams shows the effects of ADH on various structures within the body. In the brain, ADH affects the cerebrum by influencing social behavior in some mammals. ADH is also produced in the brain by the hypothalamus and released in the posterior pituitary. ADH also constricts arterioles in the body, which are the small arteries that enter into capillary beds. Finally, a kidney is shown because ADH increases the reabsorption of water in the kidneys.
ADH is produced in the hypothalamus and released by the posterior pituitary gland. It causes the kidneys to retain water, constricts arterioles in the peripheral circulation, and affects some social behaviors in mammals.

ADH has two major effects. It constricts the arterioles in the peripheral circulation, which reduces the flow of blood to the extremities and thereby increases the blood supply to the core of the body. ADH also causes the epithelial cells that line the renal collecting tubules to move water channel proteins, called aquaporins, from the interior of the cells to the apical surface, where these proteins are inserted into the cell membrane ( [link] ). The result is an increase in the water permeability of these cells and, thus, a large increase in water passage from the urine through the walls of the collecting tubules, leading to more reabsorption of water into the bloodstream. When the blood plasma becomes less concentrated and the level of ADH decreases, aquaporins are removed from collecting tubule cell membranes, and the passage of water out of urine and into the blood decreases.

Aquaporins

This diagram depicts a cross section of the right wall of a kidney collecting tubule. The wall is composed of three block-shaped cells arranged vertically one on top of each other. The lumen of the collecting tubule is to the left of the three cells. Yellow-colored urine is flowing through the lumen. There is a small strip of blue interstitial fluid to the right of the three cells. To the right of the interstitial fluid is a cross section of a blood vessel. Arrows show that water in the urine is entering the left side of the wall cells through aquaporins. The water travels through the cells and then leaves the kidney tubule through additional aquaporins in the right side of the wall cells. The water travels through the interstitial space and enters into the blood in the blood vessel. The aquaporins in the wall cells are being released from aquaporin storage vesicles within their cytoplasm.
The binding of ADH to receptors on the cells of the collecting tubule results in aquaporins being inserted into the plasma membrane, shown in the lower cell. This dramatically increases the flow of water out of the tubule and into the bloodstream.

A diuretic is a compound that increases urine output and therefore decreases water conservation by the body. Diuretics are used to treat hypertension, congestive heart failure, and fluid retention associated with menstruation. Alcohol acts as a diuretic by inhibiting the release of ADH. Additionally, caffeine, when consumed in high concentrations, acts as a diuretic.

Chapter review

Homeostasis requires that water intake and output be balanced. Most water intake comes through the digestive tract via liquids and food, but roughly 10 percent of water available to the body is generated at the end of aerobic respiration during cellular metabolism. Urine produced by the kidneys accounts for the largest amount of water leaving the body. The kidneys can adjust the concentration of the urine to reflect the body’s water needs, conserving water if the body is dehydrated or making urine more dilute to expel excess water when necessary. ADH is a hormone that helps the body to retain water by increasing water reabsorption by the kidneys.

Questions & Answers

what is the anatomy
FAKE Reply
Anatomy is study of structure of organs.
Sneha
thanks
FAKE
The scientific study of the structure of human or animal bodies.
FAKE
I was confused as to which one would be right and I asked
FAKE
My answer and you answer both are right.
Sneha
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AMY
what the name
isaiah
umesh. rede
Rede
what is heart and long type answer
Lalita Reply
its a organ in the body
ay
describe about hear chambers.. valves.. arteries.. veins.. circulation.. inferior/superior venacava, aorta., tricuspid valve, mitral valve. pulmonary artery/vein, how oxigenation occur,systolic presure diastolic pressure.. stroke volume,cardiac output, ets.. heart located in which place, describe it
Sanjith
if you describe what I cited up, thogh you can write a long type answer about heart
Sanjith
autonomic functions took over
Vanarith Reply
What did they take over?
Eric
what is the average volume of blood in men and why does it varrie from women?
Esther Reply
what is the average volume of blood in men
Esther
5to6liter
Sarita
5to6liter dt
Sarita
umesh. rede
Rede
what is the definition of anatomy
Noriah Reply
Search google
killer
^of
chieng
The study of the structure or internal workings of something. "Machiavelli's anatomy 
Eric
post. communi. artey... this may be true 70% hope correct
vikash Reply
what is the strongest muscle in the human body?
Robiam Reply
masseter muscles
Om
yes masseter..... jaw muscle is the strongest muscle..
Sarita
Kidneys have direct effect on which
The function the loop
function of the loop?
Eric
the function of the loop of henle is to increase surface area for reasorbtion.
Conan
what is an atom and it's functions
Jany
An atom is the basic building block of matter.
Eric
which is the largest digestive gland in our body
Shubu
stomach
Barbara
What is the smallest bone in the body of the human being?
Kelvin
pisiform
Chulit
how many found in the head
obakunmi
4
ayesha
I think stapes is the smallest bone in human body
Sanjith
22
Sanjith
yes stapes is the smallest bone of our body
Sarita
the smallest bone is stapes in the ear
Isaac
smallest bone in human body is stapes or stirrup present in the middle ear ..
Om
stapes yes
Robiam
blood work and purification and it leads to cardiac systen
vikash
explain function of kidney
Noel Reply
filtration
Naqash
Secretagogue hormones
Sa
Organising water
Sa
hi
Jany
they help in the reproduction of sperms
Jany
Their main job is to cleanse the blood of toxins and transform the waste into urine. The kidney have several functions though. I think it is important to know them, but not in depth. But to truly understand the kindney's over all importance.
Eric
I meant to say the kidneys have.
Eric
how kidney help in reprdution of sperms?
Amir
the basic and functinal unit of kidney is Nephron
Sanjith
what us the name of the longest bone in the body
Ohuche Reply
femur
Zaini
femur
AKHILA
anatomical planes of the body
Opio Reply
sagittal plane, transverse plane and coronal plane
Ogechi
the only moveable bone in head
Sewar Reply
the only movable bone in head
Sewar
stapes. in the ear. but one could argue, all three ear bones move. malleus, Incas, and stapes.
Conan
mandible
Ankita
The mandible is.
Eric
The only unattached bone in the body is the hyod bone in the neck.
Eric
The mandible. It's the part that enables us to talk.
chieng
Mandible present in the head
Shubu
how can u protect ur self from corona
Nity Reply
how can u know that u have corona
Nity
with a test
Danielle
can protect by social distancing, following hand hygiene and standard precautions
Danielle
tq very much
sudhakar
as per the CDC incubation period 2 to 14 days. typical symptoms. typical symptoms, fever, cough, malagia, fatigue, and shortness of breath. alcohol based hand sanitizers. 60 to 85% strength, physical barriers, PPE. a face mask with three layers. Keep a physical distance of 6 feet or more.
Conan
a nasal swab test, or a blood test to confirm SARs-cov-19.
Conan
what is corona
Nity Reply
virus
Danielle
It's a virus which causes COVID 19
chieng

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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