B12 - Homeostasis In Action (Y11 - Autumn 1)

Question 1

🟢 How Is Body Temperature Kept In Check?

Answer 1

Body temperature is monitored and controlled by the thermoregulatory centre in the brain. The thermoregulatory centre contains receptors sensitive to the temperature of the blood. The skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre.

Question 2

🟢 How Does Your Body React When Your Body Temperature Is Too High

Answer 2

If the body temperature is too high, blood vessels dilate (vasodilation) and sweat is produced from the sweat glands. Both these mechanisms cause a transfer of energy from the skin to the environment.

Question 3

🟢 How Does Your Body React When Your Body Temperature Is Too Low

Answer 3

If the body temperature is too low, blood vessels constrict (vasoconstriction), sweating stops and skeletal muscles contract (shiver).

Question 4

🟢 How Does The Body Cool Itself Down (How Does The Body React, What Does It Do)

Answer 4

When your core body temperature begins to rise, impulses are sent from the thermoregulatory centre to the body so more energy is transferred to the surroundings to cool you down:

• The blood vessels that supply your surface skin capillaries dilate (open wider). This is called vasodilation and it lets more blood flow through the capillaries. Your skin flushes, so you transfer more energy by radiation from your skin to the surroundings, cooling you down and warming the air around you
• You produce more sweat from the sweat glands in ykur skin. This extra sweat cools your body down as water evaporates from yoir skin, transferring energy to the environment. In humid wearher when the water in sweat does not evaporate it is much harder to keep cool.

As you lose more water through sweating when it is hot or you are exercising hard, it is inportant to take in more water and mineral ions through your drink and food to balance this loss.

Question 5

🟢 How does the Body Warm Itself Up

Answer 5

If your core body temperature starts to fall, impulses are sent from your thermoregulatory centre to the body to prevent you cooling down, reducing energy transfer to the environment.

• The blood vessels that supply your skin capillaries constrict (close up) to reduce the flow of blood through the capillaries. This vasoconstriction reduces the energy transferred by radiation through the surface of the skin.
• Sweat production is reduced or stopped. Less water from sweat evaporates, so less energy is transferred to the environment.
• Your skeletal muscles contract and relax rapidly, causing you to shiver. These muscle contractions need lots of respiration, an exothermic process. The energy transferred from these exothermic reactions raises your body temperature until the shivering stops.

Question 6

🟢 What is the 1st thing in the body that anticipates getting hotter or colder? (+What is the last thing that takes in the feedback)

Answer 6

1st Line of Defence: Peripheral Thermoreceptors detect when it’s cold so the body starts to do things to warm up/cool down before your body temperature has gone too high/too low.

The Hypothalomus is where the feedback for how the body has helped to warm up/cool down the body

Question 7

🟢 What Are The Two Main Poisonous Waste Products

Answer 7

There are two main poisonous waste products - carbon dioxide and urea. They cause major problems for your body if their levels are allowed to build up.

Question 8

🟢 Why And How Is Carbon Dioxide Removed From The Body (+ How Is It Produced)?

Answer 8

The carbon dioxide produced by the body cells during respiration must be removed because dissolved carbon dioxide produces an acidic solution. This would affect the working of all the enzymes in your cells. The carbon dioxide diffuses out if the cells into your blood down a concentration gracient. It diffuses from the blood into the air in the alveli of your lungs. The air containing the excreted carbon dioxide is removed from your body when you exhale (however exhaling means you lose water when the moist air from your lungs breathed out).

Question 9

🟢 What Is Urea Made Up Of?

Answer 9

Urea is the nitrogenous waste produced by the breakdown of excess amino acids in your liver.

Question 10

🟢 Why And How Is Urea Removed From The Body

Answer 10

The urea passes from the liver cells into your blood. Urea is poisonous and if levels build up in your body, this will cause extensive damage to the cells. Fortunately, it is filtered out of your blood by your kidneys and is then passed out of the body in the urine produced by the kidneys, along with any excess water and salt.

Question 11

🟢 How Are Proteins Digested And The Waste Removed? (What Happens To Excess Amino Acids

Answer 11

The digestion of proteins from the diet results in excess amino acids which need to be excreted safely. In the liver these amino acids are deaminated to form ammonia. Ammonia is toxic and so it is immediately converted to urea for safe excretion. (The rest of the amnio acid molecule can then be used in respiration or to make other molecules.)

Amino Acids (deaminated) —-> (deaminated) Ammonia —-> Urea —-> Excretion

Question 12

🟢 Why Is Water and Mineral Ion Balance Maintained In The Body?

Answer 12

The removal of urea from the body is part of the system you use to balance the concentrations of water and mineral ions in your body fluids. If the cells of your body lose or gain too much water by osmosis to the fluids surrounding them, they can’t function properly. This means that water, mineral ions, amd urea are let out if the hody to maintain the balance.

Question 13

🟢 What Ways Are Water, Mineral Ions, And Urea Lost From The Body?

Answer 13

• Water leaves the body via the lungs during exhalation.
• Water, ions and urea are lost from the skin in sweat.
• There is no control over water, ion or urea loss by the lungs or skin.
• Excess water, ions and urea are removed via the kidneys in the urine.
• If body cells lose or gain too much water by osmosis they do not function efficiently.

Question 14

🟢 What Ways Give No Control To The Amount Substances Lost To The Environment When Mainatining Water And Nitrogen Balance?

Answer 14

• Water leaves the lungs every time you exhale

- Water, mineral ions, and urea are lost through the skin in sweat

Question 15

🟢 What Ways Give Control To The Amount Substance Lost To The Environment When Mainatining Water And Nitrogen Balance?

Answer 15

Urea, excess water, and excess mineral ions are removed from the body via the kidneys, then excreted in the urine. This process is very tightly regulated to:

• Maintain the water and mineral ion content of the blood within narrow limits, and
• Remove urea (the poisonous nitrigenous waste)

Question 16

🟢 What Is Deamination?

Answer 16

Deamination is the removal of an amino group from an amino acid or other compound..

Question 17

🟢 The Difference Between Excretion and Egestion

Answer 17

Excretion is the process where an organism excretes the byproduct of a metabolic process using the different cellular and organ functions. Egestion, on the other hand, is the term associated with the excretion or elimination of undigested food from the digestive system of an animal.

Question 18

🟢 Function Of The Kidney (What Does It Do)

Answer 18

Your kidneys remove toxic urea from the body in your urine, along with any excess water and mineral ions not need by the body. Urine is produced comstantly by your kidneys and stored temporarily in your bladder. The exact quantities depend on what you have taken in and given out.

Question 19

🟢 What Do Your Kidneys Do When You’re Short On Water (+What Effect Does This Have On The Urine)

Answer 19

If you are short of water, your kidneys conserve it. You produce very little, very concentrated urine and water is saved for use in your body. If you drink too much water, then your kidneys produce lots of dilute urine to get rid of the excess.

The amount of water resbsorbed into the blood is controlled by a very sensitive feedback mechanism that makes sure the water balance of your body fluids and cells is always within a narrow range.

Question 20

🟢 How Do The Kidneys Produce Urine? (Filtration and Selective Reabsorption)

Answer 20

The kidneys produce urine by filtration of the blood and selective reabsorption of useful substances such as glucose, some ions and water.

Question 21

🟢 How Is Water Level In The Body Controlled

Answer 21

The water level in the body is controlled by the hormone ADH which acts on the kidney tubules.

Question 22

🟢 What Happens To Glucose, Water, And Mineral Ions After The Blood Has Been Filtered?

Answer 22

All of the glucose is reabsorbed back into the blood by diffusion and active transport. However the amount of water and dissolved mineral ions that are reabsorbed varies. It depends on what is needed by your body. This is known as selective reabsorbtion.

The amount of water reabsorbed into the blood is controlled by a very sensitive feedback mechanism that makes sure the water balance of your body fluids and cells is always kept within a narrow range.

Question 23

🟢 What Does ADH Do When Blood Plasma Becomes Too Concentrated, Where Is It Secreted, And How Is It Controlled?

Answer 23

The water level in the body is controlled by the hormone ADH which acts on the kidney tubules. ADH is released by the pituitary gland when the blood is too concentrated and it causes more water to be reabsorbed back into the blood from the kidney tubules. This is controlled by negative feedback.

Question 24

🟢 What Does ADH Do When Blood Plasma Becomes Too Dilute

Answer 24

If the solute concentration becomes too dilute, less ADH is released into the blood. Less water is reabsorbed in the kidney tubules, so you produce a large volume of dilute urine and the blood solute concentration returns back to normal.

Question 25

🟢 How Are People With Kidney Failure Treated?

Answer 25

People who suffer from kidney failure may be treated by organ transplant or by using kidney dialysis.

Question 26

🟢 What Are The Two Main Methods For Treating Kidney Failures

Answer 26

Dialysis - the function of the kidney is carried out artificially

Kidney Transplant - the failed kidneys can be replaced with a healthy one

Question 27

🟢 How Does A Dialysis Machine Work (+It’s Function/What Does It Do)

Answer 27

A dialysis machine relies on the process of dialysis to clean the blood. In a dialysis machine, a person’s blood leaves their body and flows between partially permeable membranes. On the other side of these membranes is the dialysis fluid. The dialysis fluid contains the same concentration if useful substances as the blood of a healthy person.

Question 28

🟢 How Does Dialysis Work

Answer 28

In dialysis, it’s vital that patients lose the excess urea and mineral ions that have built up in the blood, but it’s just as importamt that no useful substances (glucose and some mineral ions) are not lost.

The loss of useful substances is prevented by the control of dialysis fluid, which contains the same concentration of glucose and mineral ions as the blood of a person without kidney disease. This ensures there is no net movement of glucose out of the blood. As the dialysis fluid contains normal plasma levels of mineral ions, any excess ions are removed by the blood by diffusion. The excess ions move out of the blood into dialysis fluid by diffusion down a concentration gradient, leaving the blood plasma concentration of mineral ions at normal levels.

In contrast, the dialysis fluid contains no urea. This makes a steep concentration gradient from the blood down to the fluid. As a result, much of the urea leave the blood. The whole process of dialysis depends on diffusion down concentration gradients, which have to be maintained by the flow of a fluid. There is no active transport

Question 29

🟢 Dialysis Advantages

Answer 29

• Treatment by dialysis restores the concentrations of urea and mineral ions to normal levels.
• For many people, dialysis acts as an artificial kidney that keeps them alive
• There are no shortages of dialysis machines (whereas there are a shortage of donor kidneys)

Question 30

🟢 Dialysis Diadvanatges

Answer 30

• Dialysis has to be repeated at regular intervals
• Someone on dialysis has to control their protein intake carefully between sessions to keep to keep urea levels low.
• Someone will also have to control the amount of salt they eat as their kidneys cannot get rid of excess mineral ions
• Many people have dialysis in hospital, but some people have dialysis machines at home
• It’s expensive in the long term

Question 31

🟢 What Is The Main Problem With Kidney Transplants

Answer 31

The main problem with transplanting a kidney is that the new kidney comes from a different person. The antigens (proteins on the cell surface) of the donor organ will be different to those of the recipient. There us a risk that the antibodies of the immune system of the recepient will attack the antigens of the donor organ. This results in rejection an ddestruction of the donated kidney.

Question 32

🟢 How Can The Risk Of Rejection Be Minimised With Kidney Transplants

Answer 32

There are many ways of reducing the risk of rejection. These include:

• Making sure the match between the donor and recepient is as close as possible (we can use a donor kidney with a ‘tissue type’ very similar to the recepient
• The recepient can be given immunosuppressant drugs for the rest of their lives. Immunosuppressant drugs are improving all of the time and help to prevent the rejection of a new organ, however these drugs hinder that a patient’s immune response to diseases.

Question 33

🟢 Advantages Of Kidney Transplants

Answer 33

• If you recieve a kidney transplant, you’re free from restrictions that come with regular dialysis. (You can eat and drink what you want)
• There are increasing numbers of live donor transplants where a family member or someone with a tissue match donates one of their kidneys
• It’s only expensive in the short term (as you don’t need to go back for more treatments)
• In 2011, scientists grew functioning embryonic kidney tissue from stem cells. Perhaps in the future, whole new kidneys can be grown, maybe without the antigens that trigger the immune reaction, o patients would not long need immunsuppressant drugs

Question 34

🟢 Disdavantages Of Kidney Transplants

Answer 34

• Disadvantages of immunosuppressant drugs are that they prevent patients from dealing with infection diseases as effectively
• Transplanted organs don’t last forever. Once the organ starts to fail, the patient has to return to dialysis and wait for another suitable kidney
• Any surgery comes with risks, as you’re given an anaethetic

Question 35

🟢 Dialysis VS Kidney Transplant

Answer 35

Dialysis:

• No shortage of dialysis machines
• Requires frequent treatments and a controlled diet
• Expensive in the long term

Kidney Transplant:

• Shortage of kidney donors
• Allows patient to lead a normal life
• Only expensive initially
• Patients have to take anti-rejection drugs for the rest of their life
• Any surgery comes with a risk, as you’re given an anaesthetic