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Biology > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

What is homeostasis?

A

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

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2
Q

What body conditions are controlled?

A

-Body temperature
-Water levels
-Blood glucose concentration

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3
Q

How does the body maintain a stable environment?

A

Using negative feedback

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4
Q

How does negative feedback work?

A
  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
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5
Q

Where does the body gain heat from?

A

respiration and the environment

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6
Q

Where does the body lose heat to?

A

to the environment through the skin

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7
Q

Why must body temperature remain constant?

A

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

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8
Q

What monitors body temperature?

A

Thermoregulatory receptors in the brain

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9
Q

Where are the thermoregulatory receptors?

A

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

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10
Q

How is temperature controlled?

A

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

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11
Q

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

A
  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
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12
Q

What are the three responses to combat heat?

A

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

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13
Q

What are the three responses to combat cold?

A

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

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14
Q

Why does blood glucose concentration vary?

A
  • absorbing glucose into blood after digesting a meal
  • cells respiring and using up glucose
  • exercising removing glucose from the blood
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15
Q

How is blood glucose concentration controlled?

A

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

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16
Q

What happens if blood glucose concentration is too high?

A

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.

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17
Q

What happens if blood glucose concentration is too low?

A

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.

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18
Q

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

A

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.

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19
Q

What is diabetes?

A

When hormones cannot be used to control blood glucose concentration.

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20
Q

What is Type 1?

A

When the pancreas releases too little/no insulin

21
Q

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

A
  • 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
22
Q

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

A

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.

23
Q

What is Type 2?

A

When body cells no longer respond when insulin is produced

24
Q

How is type 2 diabetes developed?

A

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

25
Q

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

A
  • Reduce carbohydrate intake - especially reducing amount of sugar eaten.
  • Regular exercise
26
Q

What are some treatments for diabetes?

A
  • 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).
27
Q

What do the kidneys control?

A

concentration of urea, ions and water in the blood

28
Q

What is removed from the blood in the kidneys?

A

all urea and then excess water and ions

29
Q

Why does the pancreas remove all urea?

A

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).

30
Q

Why does the pancreas remove excess ions?

A

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.

31
Q

Why does the pancreas remove excess water?

A

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.

32
Q

What are the three stages within the kidneys?

A

1 - Filtration
2 - Selective Reabsorption
3 - Formation

33
Q

What happens in the kidneys during filtration?

A

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

34
Q

What happens in the kidneys during selective reabsorption?

A

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

35
Q

What happens in the kidneys during formation?

A

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

36
Q

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

A

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

37
Q

Why do water levels change throughout the day?

A
  • drinking water/fluids
  • sweating
  • lost when breathing out
38
Q

How is urine affected by water concentration?

A

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

39
Q

What is the relationship between ADH and water conservation?

A

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

40
Q

What happens when water concentration is not optimum?

A
  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
41
Q

What happens if the kidneys don’t function properly?

A

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.

42
Q

What are the symptoms of kidney failure?

A

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

43
Q

How can we treat kidney failure?

A

Using dialysis or a kidney transplant

44
Q

What does dialysis do?

A

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

45
Q

How does dialysis work?

A
  • 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.
46
Q

What are the positives of dialysis?

A

Buys patient time until transplant donor is found.

47
Q

What are the negatives of dialysis?

A
  • 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
48
Q

What are the negatives of a kidney transplant?

A
  • Risk of rejection (must take immunosuppressants)
  • Risk of infection (during operation)
  • Long wait time (for a tissue match)
49
Q

What are the positives of a kidney transplant?

A
  • 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

Biology (5 decks)

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