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Biology > Topic 5-Homeostasis and Response > Flashcards

Topic 5-Homeostasis and Response Flashcards

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1
Q

What is homeostasis?

A

The maintenance of constant internal environments.

Mechanisms are in place to keep optimum conditions despite internal and external changes. Needed for enzyme action and all cell functions

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2
Q

What does homeostasis control?

A
  • Blood glucose concentration
  • Body temperature
  • Water levels
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3
Q

What do all control systems have?

A
  • Receptors
  • Coordination centres
  • Effectors
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4
Q

What do receptors do?

A

Cells that detect stimuli (changes in the environment)

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5
Q

What do coordination centres do?

A

They process the information received from the receptors e.g brain, spinal cord and pancreas

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6
Q

What do effectors do?

A

They bring about responses to bring the conditions in the body back to optimum levels e.g muscles or glands

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7
Q

What are methods used by scientists to determine brain function?

A
  • Studying patients with brain damage
  • Electrical stimulation of the brain using an electrode
  • MRI scans
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8
Q

What does the endocrine system do?

A

It sends hormones (chemical messengers) around the body. When they reach a target tissue they produce a response. It is made up of glands which secrete hormones directly into the bloodstream

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9
Q

What is the pituitary gland and what does it do?

A
  • The master gland
  • Secretes hormones into the blood to either have an effect on the body or act on other glands to stimulate to produce different hormones
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10
Q

What is the pancreas and what does it do?

A
  • Releases insulin

- Controls blood glucose levels

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11
Q

What is the thyroid and what does it do?

A
  • Releases thyroxine

- Controls metabolic rate, heart rate and temperature

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12
Q

What is the adrenal gland and what does it do?

A
  • Releases adrenaline

- Is involved in the ‘fight or flight’ response

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13
Q

What is the ovary and what does it do?

A
  • Releases oestrogen

- Is involved in the menstrual cycle and the development of female secondary sexual characteristics

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14
Q

What are the testes and what do they do?

A
  • Releases testosterone

- Is involved in the production of sperm and the development of male secondary sexual characteristics

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15
Q

What are the effects of adrenaline?

A
  • Increase in heart and breathing rate (delivers oxygen and glucose to the body)
  • Stored glycogen converted to glucose
  • Dilation of pupils
  • Increases mental awareness
  • Blood diverted away from digestive system to muscles
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16
Q

What is the thermoregulatory centre?

A
  • Monitors and controls body temperature
  • Found in the brain
  • Has receptors that monitor the temperature of blood
  • Has receptors in the skin that send impulses to the thermoregulatory centre
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17
Q

What stimuli are the receptors of the eye sensitive to?

A

Light intensity and colour

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18
Q

What is the function of the nervous system?

A

The nervous system allows the body to react to its surroundings and coordinate an appropriate response

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19
Q

What is a hormone?

A

A hormone is a chemical messenger secreted by a gland. It travels in the blood to a target organ, where it causes a responses

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20
Q

What type of organ secretes hormones?

A

Glands

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21
Q

Which organ monitors and controls blood glucose concentration?

A

The pancreas

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22
Q

How does the pancreas respond when blood glucose levels are too high?

A

The pancreas secretes the hormone insulin

Insulin binds to cell in target organs (muscles and liver) causing glucose to move from the blood into muscle cells for respiration

It also causes excess glucose to be converted into glycogen which is stored in the liver

The blood glucose concentration is reduced

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23
Q

What happens when the human body temperature becomes too high?

A

Sweat (evaporates from skin surface resulting in increased energy transfer away from body) is produced by sweat glands

Vasodilation means more blood flows closer to the surface of the skin, resulting in increased energy transfer from the body and into the surroundings, resulting in more heat loss

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24
Q

What happens if the human body temperature becomes too low?

A

Sweating stops

Skeletal muscles contact rapidly (shivering) to generate heat from respiration

Hairs stand on end to create an insulating layer, trapping warm air

Vasoconstriction means blood does not flow so close to the surface, resulting in less heat lost

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25
Q

How does the pancreas respond when blood glucose levels are too low?

A

The pancreas secretes the hormone glucagon.

Glucagon binds to liver cells causing glycogen to be broken down into glucose

Glucose is released into the blood, increasing the blood glucose concentration

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26
Q

How is blood glucose concentration controlled using a negative feedback loop?

A

When the blood glucose concentration rises or falls below the optimum, a hormone is secreted by the pancreas to oppose the change

The action of either hormone (insulin or glucagon) helps bring back the concentration to the correct level

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27
Q

What is type 1 diabetes?

A

Type 1 diabetes is an autoimmune disorder in which the pancreas does not produce sufficient insulin to control the blood glucose concentration

Glucose is excreted with urine and lots of urine is produced leaving the individual very thirsty. It also makes them tiredness and weight loss

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28
Q

How can Type 1 diabetes be treated?

A

It is treated with insulin injections at meal times, which results in glucose being taken up from the bloodstream

It is also advised to limit the intake of simple carbohydrates which contain lots of glucose

Doctors are attempting to cure diabetes with pancreas and pancreatic cell transplants, and genetically engineering pancreatic cells from mice to make insulin

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29
Q

What is Type 2 diabetes?

A

Type 2 diabetes is a disorder in which the body cells no longer respond to insulin, leading to an uncontrolled blood glucose concentration

Blood glucose levels can rise to a fatal amount

Obesity and increasing age is a risk factor for this disease

30
Q

How can Type 2 diabetes be treated?

A

Following a carefully-controlled diet, reducing the number of simple carbohydrates in diet

Doing regular exercise

Losing weight

There are also drugs to make insulin more effective on body cells, help the pancreas make more insulin or reduce the amount of glucose absorbed from the gut

31
Q

What is osmosis?

A

It is the process by which water molecule move from place where they are in high concentration to a place where they are in low concentration

32
Q

In what ways is water lost from the body

A

During exhalation via the lungs

Sweating

Urine (some is reabsorbed in the kidney)

33
Q

In what ways are ions lost from the body?

A

They are taken into the body via food

If the ion concentration is incorrect, then too little or too much water may enter body cells

This is because the water potential of the blood would be altered

They are lost in sweat

In the kidneys, certain amounts of ions are reabsorbed into the blood after it has been filtered to ensure the concentration in the blood is maintained

34
Q

What happens when the water concentration of the blood increases?

A

Cells in the body take up water

This is because the concentration of water in the bloodstream is higher than the concentration of water in the cells so water moves into the cells by osmosis

Cells then expand as they take up more water, and may eventually burst

35
Q

What happens when the water concentration of the blood decreases?

A

Cells in the body lose water

This is because the concentration of water in the bloodstream is lower than the concentration of water in the cells so water moves out of the cells by osmosis

Cells shrink as they lose water

36
Q

How are excess amino acids excreted from the body?

A

Amino acids are the products of the digestion of proteins

Amino acids are deaminated in the liver to form ammonia. As ammonia is toxic it is converted to urea

It is lost in sweat

In the kidneys it is filtered out of the blood

37
Q

How do the kidneys maintain the balance of water and other substances in the body?

A

Filtering out the waste products

Selectively reabsorbing useful substances such as glucose, ions and water

38
Q

What is the full name of the hormone ADH?

A

Anti-diuretic hormone

39
Q

Where is ADH secreted in the body?

A

It is released into the pancreas by the pituitary gland of the brain

40
Q

How does ADH affect the reabsorption of water in the kidneys?

A

When the blood is too concentrated, the pituitary gland secretes more ADH

ADH travels in the bloodstream to the kidney and increases the permeability of kidney tubules to water

More water is reabsorbed in the kidneys, resulting in a smaller volume of more concentrated urine

41
Q

Why is kidney failure dangerous?

A

When the kidneys are damaged, they may be unable to filter the blood properly. This may lead to:

A build-up of toxic molecules like urea in the body

An uncontrolled ion and water balance and cells being damaged as a result of osmosis

42
Q

What are the two ways of treating people with kidney failure?

A

Dialysis

Kidney transplants

43
Q

How does dialysis work?

A

Dialysis is when the function of the kidneys is carried out using an artifical membrane

Blood moves between partially permeable membranes surrounded by dialysis fluid.

Dialysis fluid has the same concentrations as ions and glucose as healthy blood

Useful ions and glucose are not lost from the blood but urea, excess ions and water diffuse across the membrane

44
Q

What are some of the advantages and disadvantages of dialysis?

A

It acts as an artificial kidney and keeps people alive while they wait for a transplant

It has to be done three times a week, with the process itself taking three to four hours

Blood clots could form and you have to follow a strict diet

It is generally unpleasant and the build up of waste products between sessions can leave you feeling ill

45
Q

What are the advantages and disadvantages of kidney transplants?

A

The person does not need to visit the hospital as regularly as they did when undergoing dialysis and it is cheaper than the overall cost of dialysis

The main problem is that they could be rejected from the body as a result of the immune system recognising the antigens on the donor organ as foreign

The chance of this happening can be reduced by using immunosuppressant drugs

However, this means that the person can be left vulnerable to other diseases. In addition, transplanted kidneys do not last forever

High initial cost

Shortage of donors

Infection during/after surgery

46
Q

What is tropism?

A

A tropism is the response of a plant to a specific stimulus

47
Q

What is phototropism?

A

Phototropism is the response of a plant’s shoot or root to light

48
Q

What is gravitropism?

A

Gravitropism is the response os a plant’s shoot or root to gravity

49
Q

What is auxin?

A

Auxin is a hormone which controls the growth of a plant’s shoots and roots.

When auxin is unevenly distributed in a growing plant, the rate of growth will also be unequal

50
Q

How do plant shoots show positive phototropism?

A

One side of the shoot is in the light, causing auxin to move to the shaded side

At the shaded side, the cells are stimulated to grow- the shoot bends towards the light

As a result, photosynthesis can occur at a faster rate

51
Q

How do plant shoots show negative gravitropism?

A

In a horizontal shoot, auxin accumulated in the lower side due to gravity

Cells on the lower side of shoot grow more, causing the shoot to bend away from the direction of gravity

As a result, more light is usually available for photosynthesis

52
Q

How do plant roots show positive gravitropism?

A

In a horizontal root, auxin accumulates in the lower side, causing cells to grow less

The root bends in the direction of gravity

As a result, more water and nutrients are available to the plant roots

53
Q

What are gibberllins?

A

Gibberellins are a type of plant hormone involved in seed germination

54
Q

What is ethene?

A

Ethene is a type of plant hormone involved in cell division and ripening

55
Q

How does light intensity affect plant growth? (Practical)

DV, IV and CV

A

IV: Distance between light and petri dish

DV: Height of plant

CV: Same number of seeds per petri dish, power of lamp, type of seed, volume of water added daily, temperature

56
Q

How does direction of light affect plant growth? (Practical)

DV, IV and CV

A

IV: Direction of light source

DV: Direction of plant growth

CV: Same number of feeds per petri dish, power of lamp, type of seed, volume of water added daily, temperature, distance between lamp and seeds

57
Q

How does the angle of the petri dish affect plant growth? (Practical)

IV, DV and CV

A

IV: Angle of petri dish

DV: Direction of plant growth

CV: Same number of seeds per petri dish, power of lamp, type of seed, volume of water added daily, temperature, distance between lamp and seeds, direction of light source

58
Q

How does light intensity affect plant growth?

Instructions

A

First, place cotton wool in three petri dishes and the soak them with equal volumes of water

Then place ten mustard seeds in each dish

Next, leave the dishes in a warm place and allow the seeds to germinate

We need to water the seeds every day with the same volume of water

Once the seeds have germinated, we need to make sure that the three dishes have the same number of seedlings (take out ones that haven’t germinated and take more out of the other dishes to match)

Next, use a ruler to measure height of each seedling. Hold stems to keep them straight but be careful to not damage the seedlings

Place the three in different conditions (full sunlight, partial light and total darkness)

Measure height of each seedling every day for at least 5 days then calculate mean for each day

59
Q

What is meant by metabolic rate?

A

Rate of chemical reactions in the body

60
Q

Give two functions of plant roots

A

Absorb water from the soil

Absorb minerals and nutrients

Provides anchorage/support

61
Q

“People with the muscles disease are not able to store glycogen in their muscles

Suggest an explanation for the difference in results”

A

Cannot store sugar as glycogen so they need to receive glucose from somewhere else for respiration

62
Q

Megapode birds:

  • Dig a large hole in sand
  • Fill the hole with dead plants
  • Lay their eggs on top of the dead plants
  • Cover the surface with a thick layer of sand

The dead plants in the nest decay. The decaying process helps to keep eggs warm for many weeks

Suggest how

A

Microorganisms respire and respiration releases thermal energy

63
Q

“Four days after a digester was first set up, the biogas contained a high percentage of carbon dioxide

Suggest an explanation for this”

A

CO2 is produced by aerobic respiration

Oxygen present

Not much methane

64
Q

The human body is kept at a constant internal temperature of about 37 degrees Celsius

Body temperature is monitored and controlled by the thermoregulatory centre in the brain

Describe what happens in the body to keep the body temp constant

A

There are temperature receptors in the TC and in the skin. The ones in the skin send impulses to the TC, giving information about skin temperature

If the core body temperature is too high: vasodilation (more blood flows through the skin and more heat is lost)

If core body temperature is too low, blood vessels supplying the skin capillaries constrict to reduce the flow of blood and therefore less heat is lost

65
Q

“Describe and explain the different patterns shown in the core body temperature and skin surface temperature between 9.15 and 10.15”

A

Increase in core temperature due to increase in respiration which releases energy as a water product

Skin temp decreases because there is sweating which evaporates and cools the skin

66
Q

“During a race, a cyclist’s blood glucose concentration began to decrease.

Describe how the body responds when the blood glucose concentration begins to decrease

A

Pancreas detects low blood glucose

Produces glucagon

Glycogen is converted to glucose

67
Q

Homeostasis keeps conditions in the body relatively constant. The amount of water in the body is controlled by homeostasis

Kidney function is controlled by a gland in the brain

Describe how the water content of the blood is controlled

A

If water content is too low, ADH is released from the pituitary gland into the blood

Kidney reabsorbs more water and causes more concentrated urine to be produced

If water content is too high, ADH is lowered

Less water is reabsorbed by kidney

More dilute urine produced

68
Q

Describe how a healthy kidney produces urine

A

The kidney filters the blood

Reabsorbs all of the glucose and some or the ions

Reabsorbs some of the water

Releases urea

69
Q

Marathon runners often drink sports drinks during/after a race

Explain why

A

To replace water/ions/salts lost in sweat

70
Q

An athlete can run a marathon in 2 hours 15 minutes on a dry day in outside temperatures up to 35 °C.

If the air is dry, his body will not overheat.

In humid conditions the same athlete can run the marathon in the same time.

However, in humid conditions, if the outside temperature goes over 18 °C then his body will overheat.

Suggest an explanation for the athlete overheating in humid conditions.

A

Sweat released cannot evaporate because of high humidity/all the water vapour

Therefore less heat is lost

Biology (8 decks)

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