B12 - Homeostasis In Action

Question 1

It is really important that the body keeps the level of water in the blood as constant as possible .

Answer 1

-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 .

Question 2

-If body cells gain or loose too much water by osmosis , they don;t work effiecntly .

Answer 2

-So the body ahs a system in place to maintain its water balance , This is part of HOMEOSTASIS .

Question 3

tHE BODY taken in water through good and dirnk , but what is one wy th ebody can lose water ?

Answer 3

We can lose water via the LUNGS , when we EXHALE .
-The body has no way to control this water loss .

Question 4

Another way the body can lose water ?

Answer 4

-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 .

Question 5

What is the finaly way the body can lose water ?

Answer 5

-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 .

Question 6

-How do the kindeys remove urea s1 ?

Answer 6

-Humans have two kidneys .
-Blood enters he kindey through an artery . This blood contains the waste prodcuts urea .

Question 7

-How do the kindeys remove urea s2 ?

Answer 7

-The kindeys remove this urea , as well as ecess ions and eccess water .

Question 8

-How do the kindeys remove urea s3?

Answer 8

This leaves the kidneys as urine , and this is stored in the bladder .

Question 9

-How do the kindeys remove urea s4 ?

Answer 9

-Blood now leaves the kindey through a vein .
-Now the blood contians no urea .

Question 10

How the kidneys adjust the lvels of molecules in the blood S1?

Answer 10

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 .

Question 11

How the kidneys adjust the lvels of molecules in the blood S2?

Answer 11

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 .

Question 12

How the kidneys adjus the lvels of molecules in the blood S3?

Answer 12

-Ure , excess ions and excess water re released s urine .

Question 13

How has the concentration of glcuose after it passes through the kidneys changed

Answer 13

HAS NOT CHANGED .
-The kindeys filter glucose out of the blood then REABSORB IT ALL , back into the blood .

Question 14

How has the concentration of ions after it passes through the kindeys changed ?

Answer 14

-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 .

Question 15

How has the concenration of urea changed fterit psses through the kidneys changed ?

Answer 15

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 .

Question 16

How does the body deal with an excess of amino acids (1)

Answer 16

-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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Question 17

How water levels are controlled , person exercises on a hot day (1)

Answer 17

-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 .

Question 18

How water levels are controlled , person exercises on a hot day (2)

Answer 18

-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 .

Question 19

How water levels are controlled , person exercises on a hot day (3)

Answer 19

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 .

Question 20

wHAT HAPPENS IF THE BLOOD IS TOO DILUTE ? (1)

Answer 20

-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 .

Question 21

wHAT HAPPENS IF THE BLOOD IS TOO DILUTE ? (2)

Answer 21

-Now more urine is produced and the concentraiton of water int he blood , reutrns back to norml .

Question 22

KIDNEY DIALYSIS :

Answer 22

-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 .

Question 23

S1 kidney dialysis

Answer 23

-When a patient has kidney failure , their blood will contain a HIGHER CONCENTRTION of water , ions and urea than it should .

Question 24

S2 kidney dialysis

Answer 24

-In kidney dialysis , the patient’s blood is passed over a SEMI-PERMEABLE membrane .

Question 25

S3 kidney dialysis

Answer 25

-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 .

Question 26

S4 kidney dialysis

Answer 26

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 .

Question 27

S5 kidney dialysis

Answer 27

-We have a concentration gradient for urea , so the urea diffuses from the blood inot the dialysis fluid .

Question 28

Why is the dialysis fluid constantly refreshed ?

Answer 28

-This ensures there is always a large concenration graident for urea .

Question 29

The dialsysis soslutionc ontrains normal concenrations of water and ions

Answer 29

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 .

Question 30

What is considered a better alternatveo f kidney dialysis ?

Answer 30

-KIDNEY TRANSPALNT - -Ina kidney transpalnt , the idseased kidney is prelaced with ah healthy kidney from a donor .

Question 31

Advanatages of dialysis

Answer 31

-No shortage of machines - you can have the treatments as soona s you need it .

Question 32

Disadvanatges of dialysis

Answer 32

-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 .

Question 33

Disadvantages of dialysis (2)

Answer 33

-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.

Question 34

Advanatges of kidney transplants

Answer 34

-Alows the patient to lead a normal life . -Only expensive initally -Eat and drink whatever . -Chepaer for the NHS overall .

Question 35

Disadvantages of kidney transplans

Answer 35

-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 .

Question 36

What is normal body temperature ?

Answer 36

37 degrees

Question 37

What is your body temperature monitored and controlled by ?

Answer 37

-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 .

Question 38

What also contains receptors ?

Answer 38

The skin also contains TEMPERATURE RECEPTROS . -These send electrical impulses down to senosry neurones to the htermoregulatory center .

Question 39

What hapens if the body temperature gets too HIGH ? e.g exercise s1

Answer 39

sweat glands release sweat onto the surfce of the skin .

Question 40

Body temperature too high s2

Answer 40

The sweat now evaporates + this takes ENERGY from the body , COOLIGN the body down .

Question 41

How is another way the body can cool itself down ?

Answer 41

-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 . -

Question 42

Another way the body cools itself down s2

Answer 42

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 .

Question 43

What happens if the body temperature drops TOO LOW .

Answer 43

-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 .

Question 44

What happens if body temperture drops too low ANOTHER WAY

Answer 44

-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 .

Question 45

Summary of the thermoregulatory center ;

Answer 45

-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 .