Homeostasis

Question 1

What is homeostasis?

Answer 1

maintaining an optimum, stable, internal environment for enzyme activity, these optimum conditions are regulated in response to changes in the internal and external environment.

Question 2

What body conditions are controlled?

Answer 2

-Body temperature
-Water levels
-Blood glucose concentration

Question 3

How does the body maintain a stable environment?

Answer 3

Using negative feedback

Question 4

How does negative feedback work?

Answer 4

1. Receptors detect a stimulus when conditions change from the optimum level
2. This information is received and processed by a coordination centre
3. Effectors respond and return conditions to the optimum level
4. It is a continuous cycle of events

Question 5

Where does the body gain heat from?

Answer 5

respiration and the environment

Question 6

Where does the body lose heat to?

Answer 6

to the environment through the skin

Question 7

Why must body temperature remain constant?

Answer 7

So that the enzymes don’t denature (if too hot) or work too slowly (if too cold)

Question 8

What monitors body temperature?

Answer 8

Thermoregulatory receptors in the brain

Question 9

Where are the thermoregulatory receptors?

Answer 9

In the thermoregulatory centre of the brain however signals are also received from receptors in the skin.

Question 10

How is temperature controlled?

Answer 10

Negative feedback system where if the temperature is too high or too low the body restores the temperature to 37°C

Question 11

What response occurs when the body’s temperature is greater or lower than 37°C?

Answer 11

1. Thermoregulatory receptors detect an change in core body temperature (in the blood)
2. Thermoregulatory processes information and sends an impulse to effectors to create a response

Question 12

What are the three responses to combat heat?

Answer 12

1- Hairs lie flat on skin: this means less insulating at is trapped and heat is transferred to the environment easily.
2- Sweat is secreted by the sweat glands: this means
that body heat is transferred to the sweat causing it to evaporate transferring the absorbed heat to the
environment
3- Arterioles (small arteries) dilate: this means more
blood flows to the surface of the skin (vasodilation). More heat energy is transferred to the environment

Question 13

What are the three responses to combat cold?

Answer 13

1- Hairs stand up on skin: this means more insulating air is trapped and less heat is transferred to the environment.
2- No/less sweat is secreted
3- Arterioles (small arteries) constrict: this means less
blood flows to the surface of the skin (vasoconstriction). Less heat energy is transferred to the environment

Question 14

Why does blood glucose concentration vary?

Answer 14

• absorbing glucose into blood after digesting a meal
• cells respiring and using up glucose
• exercising removing glucose from the blood

Question 15

How is blood glucose concentration controlled?

Answer 15

Negative Feedback. If the levels are too high or too low, they are returned to optimum.

Question 16

What happens if blood glucose concentration is too high?

Answer 16

Insulin - produced by the pancreas when receptors detects that blood glucose concentration is too high. This causes body cells to absorb glucose and use it for respiration. It also causes glucose to be absorbed by the liver/muscle cells and converted to glycogen (temporary store of glucose). Blood glucose concentration decreases, once at optimum level secretion of insulin is stopped.

Question 17

What happens if blood glucose concentration is too low?

Answer 17

Glucagon - produced by the pancreas when receptors detects that blood glucose concentration is too low. This causes liver/muscle cells to convert glycogen back into glucose which is released into the blood. Blood glucose concentration increases, once at optimum level secretion of glycogen is stopped.

Question 18

What effect can diabetes have on a person’s glycogen stores?

Answer 18

They have no glycogen stores. As a result the body has no backup of stores to act as a source of glucose. This causes weight loss and low energy.

Question 19

What is diabetes?

Answer 19

When hormones cannot be used to control blood glucose concentration.

Question 20

What is Type 1?

Answer 20

When the pancreas releases too little/no insulin

Question 21

How does someone with type 1 diabetes control blood glucose concentration?

Answer 21

• Insulin injections - these are required after eating a meal to lower blood glucose concentration. The amount of insulin needed is dependent on the person’s diet and activity levels.
• Regulate intake of carbohydrates - this is because they are broken down into glucose
• Do more regular exercise - this naturally lowers blood glucose concentration

Question 22

Where did we originally get the insulin for injections for and where do we get it from now?

Answer 22

Insulin was once taken from cows, however this was rejected by white blood cells and was causing adverse reactions so now the only thing used is human insulin. This is not as accurate as a functioning pancreas - so diabetics still have long term health issues.

Question 23

What is Type 2?

Answer 23

When body cells no longer respond when insulin is produced

Question 24

How is type 2 diabetes developed?

Answer 24

Being overweight/obese, eating sugary foods constantly or doing no exercise

Question 25

How can a person with type 2 diabetes control blood glucose concentration?

Answer 25

- Reduce carbohydrate intake - especially reducing amount of sugar eaten. - Regular exercise

Question 26

What are some treatments for diabetes?

Answer 26

- Diabetic patients may be able to have a pancreas transplant. It must be a tissue match and therefore there could be a long wait period. Immunosuppressant drugs must be taken to prevent rejection by the immune system. - In the future there is the possibility of using pancreatic stem cells to repair a pancreas that no longer produces insulin (Therapeutic Cloning).

Question 27

What do the kidneys control?

Answer 27

concentration of urea, ions and water in the blood

Question 28

What is removed from the blood in the kidneys?

Answer 28

all urea and then excess water and ions

Question 29

Why does the pancreas remove all urea?

Answer 29

Urea is removed as it is a toxic substance made by the liver. It consists of excess amino acids from digestion. It is formed through a process called deamination (turning amino acids into carbohydrates and fats) urea is the product of this process and is less toxic than the original form (ammonia).

Question 30

Why does the pancreas remove excess ions?

Answer 30

Ions, such as sodium, enter the body via food and are absorbed into the blood, they are quite often lost through sweat, if there are too many of these ions they are removed by the kidney in urine and if there is not enough they are reabsorbed by the kidney tubules.

Question 31

Why does the pancreas remove excess water?

Answer 31

Water levels if too high can cause osmosis, which can harm body cells. Dilute blood will cause red blood cells to expand and burst, concentrated blood causes red blood cells to shrink.

Question 32

What are the three stages within the kidneys?

Answer 32

1 - Filtration 2 - Selective Reabsorption 3 - Formation

Question 33

What happens in the kidneys during filtration?

Answer 33

blood is filtered in a kidney tubule, all substances apart from blood cells and larger proteins are removed from the blood.

Question 34

What happens in the kidneys during selective reabsorption?

Answer 34

any useful substances such as glucose, amino acids, some ions and some water are reabsorbed back into the blood.

Question 35

What happens in the kidneys during formation?

Answer 35

leftover substances are used to form urine, this moves down the ureter to the bladder where it is stored until it leaves the body through the urethra

Question 36

How do the kidneys control the water concentration in the blood?

Answer 36

Negative feedback controlled by the pituitary gland and a hormone known as ADH (Antidiuretic Hormone).

Question 37

Why do water levels change throughout the day?

Answer 37

- drinking water/fluids - sweating - lost when breathing out

Question 38

How is urine affected by water concentration?

Answer 38

Urine is either dilute (lots of water) or concentrated (little water)

Question 39

What is the relationship between ADH and water conservation?

Answer 39

More ADH - more water reabsorbed - lower volume and more concentrated Less ADH - less water reabsorbed - greater volume and more dilute

Question 40

What happens when water concentration is not optimum?

Answer 40

1. Brain detects low/high water concentration in blood using receptors 2. More or less ADH is released as the pituitary gland is more or less stimulated by motor neurone 3. Kidney tubule detects ADH and becomes more or less permeable to water and so more or less water is reabsorbed 4. Water concentration begins to return to optimum

Question 41

What happens if the kidneys don't function properly?

Answer 41

If the kidney's don't function properly then waste substances build up into the blood and the levels of water and ions in the blood are not controlled.

Question 42

What are the symptoms of kidney failure?

Answer 42

glucose and large proteins are present in urine urea is present in the blood

Question 43

How can we treat kidney failure?

Answer 43

Using dialysis or a kidney transplant

Question 44

What does dialysis do?

Answer 44

Removes waste substances (urea) and keeps the concentration of dissolved ions and water in the blood at normal levels.

Question 45

How does dialysis work?

Answer 45

- Patient's blood and dialysis fluid flow past each other in opposite direction inside the machine separated by a partially permeable membrane - this maintains a steep concentration gradient. - Blood cells and proteins are too big to pass through the partially permeable membrane and so they remain in the blood - The dialysis fluid contains the same concentration of dissolved ions and water as healthy blood so these substances are not lost during dialysis. - The dialysis fluid contains no urea. Urea diffuses out of the blood into the dialysis fluid.

Question 46

What are the positives of dialysis?

Answer 46

Buys patient time until transplant donor is found.

Question 47

What are the negatives of dialysis?

Answer 47

- Regular visits to hospital (3-4 times a week for 3-4 hours) - In-between treatment urea builds up - Risk of blood clots (must take anti-clotting drugs so could lose more blood when cut) - Risk of infection (repeatedly puncturing skin and blood is in contact with the machine) - Expensive - Unpleasant experience

Question 48

What are the negatives of a kidney transplant?

Answer 48

- Risk of rejection (must take immunosuppressants) - Risk of infection (during operation) - Long wait time (for a tissue match)

Question 49

What are the positives of a kidney transplant?

Answer 49

- Cheaper than dialysis - Cure for kidney failure (no need for further treatment) - No long periods of time in hospital (weekly) - Less damage to body cells/tissues (not repeatedly puncturing skin) - Only one operation (less chance of infection) - No need for anti-clotting drugs to be taken - Urea doesn't build up