B12 - Homeostasis In Action Flashcards
It is really important that the body keeps the level of water in the blood as constant as possible .
-If the blood becomes TOO DILUTE , then water moves into the cells by osmosis .
-If the blood becomes TOO CONCENTRATED , then water moves out the cells by osmosis .
-If the blood become TOO CONCENTRATED , then water moves by osmosis out of cells .
-If body cells gain or loose too much water by osmosis , they don;t work effiecntly .
-So the body ahs a system in place to maintain its water balance , This is part of HOMEOSTASIS .
tHE BODY taken in water through good and dirnk , but what is one wy th ebody can lose water ?
We can lose water via the LUNGS , when we EXHALE .
-The body has no way to control this water loss .
Another way the body can lose water ?
-When we SWEAT , we loose water through the ski .
-Sweat also contains ions such as sodium ion .
-It also c ontains waste porducts urea .
-The body cannot control how much water and ions and urea are lost by sweating .
-This is because , sweating is part of the body’s TEMPERATURE CONTROL SYSTEM .
What is the finaly way the body can lose water ?
-Body looses water via the kidneys in URINE .
-The body can control how mcuh water is lost in urine . So if the blood is too dilute , the kidneys remove the excess water and porduce greater volume of urine .
-As well as excess water , urea ad excess ions are also removed in the urine .
-How do the kindeys remove urea s1 ?
-Humans have two kidneys .
-Blood enters he kindey through an artery . This blood contains the waste prodcuts urea .
-How do the kindeys remove urea s2 ?
-The kindeys remove this urea , as well as ecess ions and eccess water .
-How do the kindeys remove urea s3?
This leaves the kidneys as urine , and this is stored in the bladder .
-How do the kindeys remove urea s4 ?
-Blood now leaves the kindey through a vein .
-Now the blood contians no urea .
How the kidneys adjust the lvels of molecules in the blood S1?
Blood passes thorugh the capillaries . Here , small molecules are filtered out of the blood .
-This includes urea , ions and water as well as the sugar glucose .
How the kidneys adjust the lvels of molecules in the blood S2?
These pass into a tube .
-Now all of the glucose , some of the ions and some of the water is reabsorbed back into the blood .
-Scientists call this SELECTIVE REABSORPTION .
How the kidneys adjus the lvels of molecules in the blood S3?
-Ure , excess ions and excess water re released s urine .
How has the concentration of glcuose after it passes through the kidneys changed
HAS NOT CHANGED .
-The kindeys filter glucose out of the blood then REABSORB IT ALL , back into the blood .
How has the concentration of ions after it passes through the kindeys changed ?
-Concentration of ions after pssing through the kidneys has decreased , kidneys filter ions out of the blood , but then reabsorb a certain amount of ions back into the blood dpeending on the needs of the body .
How has the concenration of urea changed fterit psses through the kidneys changed ?
The concentration of urea in the blood falls to virtuallly zero as it psses through the kidneys .
-That is becuase the kindeys filter out ALL THE UREA ,and do not REABSORB it all .
-All of the urea has been removd from the blood , the conentraiton of water and ions have been adjusted . Kindeys are carrying out HOMEOSTASIS .
How does the body deal with an excess of amino acids (1)
-Protiens are logn chins of amino acids , we fet a lot of protein into ur diet , when we digest this protein , amino acids pass into blood.
PROBLEM ; we often eat more protein , then the body needs then the the LIVER breaks down the exess amino acids and produces the chemical amino acids .
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How water levels are controlled , person exercises on a hot day (1)
-The body sweats to cool down ., This means the body is LOSING WATER .
-In other words , if the blood is too concentrated , the level of water in the blood FALLS.
-Then the pituitary gland releses the hormone ADH , into the blood stream .
How water levels are controlled , person exercises on a hot day (2)
-Adh travels to the KINDEYS , and it cuases the KIDNEY TURBULES to become MORE PERMEABLE (allows more watert to pass out the turbules.)
-This means water is reabsorbed from the rubules back into the blood .
How water levels are controlled , person exercises on a hot day (3)
BECAUSE OF THIS , less urine is porduced , and the amount of water in the blood rises back to its normal level .
-As the level of water in the blood returns to normal , the pituitary gland , STOPS RELEASING ADH ,
-tHIS IS ANE XAMPLE OF A negative feedback system .
wHAT HAPPENS IF THE BLOOD IS TOO DILUTE ? (1)
-If a person drinks a large amount of water . The concentration of water in the blood rises , and the pituitary glands stop releasing ADH .
-GThis means that the kidneys reabsorb LESS WATER into the blood .
wHAT HAPPENS IF THE BLOOD IS TOO DILUTE ? (2)
-Now more urine is produced and the concentraiton of water int he blood , reutrns back to norml .
KIDNEY DIALYSIS :
-In some people , their kidneys FAIL , if this happens , the level of water , ions and urea needed to be adjusted using a machine , this is called kidney dialysis .
S1 kidney dialysis
-When a patient has kidney failure , their blood will contain a HIGHER CONCENTRTION of water , ions and urea than it should .
S2 kidney dialysis
-In kidney dialysis , the patient’s blood is passed over a SEMI-PERMEABLE membrane .
S3 kidney dialysis
-This allows UREA , IONS +WATER thorugh but will not allow lrge molecules like PROTEINS to pass through . Bloodcells are also too large to pass through the membrane .
S4 kidney dialysis
On the otherside of the membrane , we have dialysis fluid .
-The dialysis fluid congtins the normal concentrations of water +ions , but DOES NOT contain any urea .
S5 kidney dialysis
-We have a concentration gradient for urea , so the urea diffuses from the blood inot the dialysis fluid .
Why is the dialysis fluid constantly refreshed ?
-This ensures there is always a large concenration graident for urea .
The dialsysis soslutionc ontrains normal concenrations of water and ions
meaning some of the water and ions will diffus from the blood into the dialsyis luid .
Because of this , conentrations of water nd ions in the patientsb lodo will reutrun tonormal .
What is considered a better alternatveo f kidney dialysis ?
-KIDNEY TRANSPALNT -
-Ina kidney transpalnt , the idseased kidney is prelaced with ah healthy kidney from a donor .
Advanatages of dialysis
-No shortage of machines - you can have the treatments as soona s you need it .
Disadvanatges of dialysis
-Patients will hve to require freueny visits to the hospittal and freqquet tratments very incovnenient .
-Also have to have a controlled diet so theyd o not produce too much urea .
Disadvantages of dialysis (2)
-Kidney dialysis is expensive in the long run .
-Takes around 8 ohurs for dialsyiss to compelte .
-Evntually dialysis cuases serous damage to the body .
-Helpingn the blood chemistrys stable gets more difficult as you get older.
Advanatges of kidney transplants
-Alows the patient to lead a normal life .
-Only expensive initally
-Eat and drink whatever .
-Chepaer for the NHS overall .
Disadvantages of kidney transplans
-Shortage of kidney donors .
-Patients need to take antirejection drugs for the rest of their lfie . As there is a risk of infection as it is someone elses kidney .
-Kidneys pnly last8-9 years.
-invsive procedure - carryies risks .
What is normal body temperature ?
37 degrees
What is your body temperature monitored and controlled by ?
-The brain .
-Scientists call this part of the brain the thermoregulatory sytem .
-The tehrmoregulatory center contains RECEPTORS which are senstive to the TEMPERATURE of the blood .
What also contains receptors ?
The skin also contains TEMPERATURE RECEPTROS .
-These send electrical impulses down to senosry neurones to the htermoregulatory center .
What hapens if the body temperature gets too HIGH ? e.g exercise s1
sweat glands release sweat onto the surfce of the skin .
Body temperature too high s2
The sweat now evaporates + this takes ENERGY from the body , COOLIGN the body down .
How is another way the body can cool itself down ?
-flushing
-under the surface of the skin , we have a fine network of blood capillaries .
-These capillariies are suplied with bloody by blood vessels deeper in the skin .
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Another way the body cools itself down s2
If we get too hot , the blood vessels supplying blood to the cappliers DILATE (get wider0 - scientists call this VASODILATION .
-As the blood vessels have dilated , MORE BLOOD flows through the cappillaries .
-Heat can now transfer OUT OF THE BLOOD so the body temperature returns back to normal levels .
What happens if the body temperature drops TOO LOW .
-In this case , blood vessels supplying the capillaries CONSTRICT (BECOME NARROWER) .
-Scientists call this VASOCONSTRICTION .
-Less blood , now flows through the capillaries and less heat is lost from the body .
What happens if body temperture drops too low ANOTHER WAY
-Shivering .
-When we shiver our skeletal muscles CONTRACT .
-To generate energy for contraction , the muscle cells ICNREASE their rate of respiration .
-This releases Heat ,w hich warms the body .
-If our body tmeperaure falls TOO LOW we also STOP SWEATING .
Summary of the thermoregulatory center ;
-In both cases the thermoregulatoryc enter detects that the body temperature has CHANGED from the normal value .
–The body responds to REVERSE THIS CHANGE + RESTORE THE NORMAL BODY TEMPERATURE .
-therefore control of body temperature is an example of HOMEOSTASIS .
