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Biology paper 2 > Homeostasis and response > Flashcards

Homeostasis and response Flashcards

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1
Q

What is homeostasis

A

the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes

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2
Q

What does homeostasis control

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

Five things that co ordinate a response

A

Stimulus
Receptor
Coordinator
Effector
Response

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4
Q

What are the various structures in a reflex arc, in order

A

Stimuli - Receptor - Sensory neurone - Relay neurone - motor neurone - effector

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5
Q

Why are reflex actions useful

A

They are automatic and rapid, they don’t involve the conscious part of the brain

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6
Q

Plan an investigation into the effect of a factor on human reaction time (6 marks)

A
  • Person A holds out their hand with a gap between their thumb and first finger
  • Person B holds the ruler with the zero at the top of the person A’s thumb
  • Person b drops the ruler at a random time, and person A must catch it
  • The number level with the top of person A’s thumb is recorded, repeat 10 times and calculate a mean
  • Swap places and repeat
  • Convert ruler measurements into reaction time
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7
Q

What does the cerebral cortex do

A

Controls consciousness, intelligence, memory and language; it is the outer part of the brain

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8
Q

What does the cerebellum do

A

Controls fine movement of muscles, and balance. Its a rounded structure at the back of the brain

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9
Q

What does the medulla do

A

Controls unconscious actions such as breathing and heart rate, found in the brain stem in front of cerebellum

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10
Q

Why is investigating the brain difficult

A
  • It is easily damaged
  • It’s complex and difficult
  • Drugs may not reach the brain because of the membranes that surround it
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11
Q

How can neuroscientists map out the brain (3 ways)

A
  • Study patients with brain damage, damaged area corresponds to what part of body it controls
  • Electrically stimulate different parts of the brain with electrode, may result in physical or mental change
  • Use MRI to create image of brain, showing what part is affected by a tumour, or which part is active during specific action
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12
Q

What are the eyes functions

A
  • Accommodation to focus on near or distant objects
  • Adaptation to dim light
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13
Q

What is the retina

A

Layer of light sensitive cells found at the back of the eye.
When light hits this the cells are stimulated, impulses are sent to the brain which interprets the information to make an image

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14
Q

What is the optic nerve

A

A nerve that leaves the eye and leads to the brain
Carries impulses from retina to brain to create an image.

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15
Q

What is the sclera

A

The strong, white outer layer which supports the structures inside the eye

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16
Q

What is the cornea

A

The see-through layer at the front of the eye. It allows light through and curved surface bends most of the light

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17
Q

What is the iris

A

The muscles that surround the pupil

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18
Q

What do the suspensory ligaments and ciliary muscles do

A

Hold the lens in place and control its shape

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19
Q

What happens to the iris in bright light

A

Radial muscles relax
Circular muscles contract
Making the pupil smaller

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20
Q

What happens to the iris in dim light

A

Circular muscles relax
Radial muscles contract
Making the pupil dilated

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21
Q

The process of accommodation on a near object

A
  • Ciliary muscles contract
  • Suspensory ligaments relax
  • Lens is thicker and more curved, refracting light more
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22
Q

The process of accommodation on a distant object

A
  • Ciliary muscles relax
  • Suspensory ligaments contract
  • The lens is thinner so less light is refracted
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23
Q

What is myopia

A

Short sightedness
When light cannot focus on the retina as the lens is too curved.
So distant objects appear blurry

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24
Q

What is hyperopia

A

Long sightedness
- Light cannot focus on the retina as the lens is too flat, so cannot refract light enough
- So close objects appear blurry

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25
Q

What are the 4 treatments to hyper and myopia

A
  • Spectacle lenses
  • Contact lenses
  • Laser eye surgery
  • Replacement lens
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26
Q

What does the thermoregulatory centre do

A

Monitors and controls body temperature

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27
Q

Where are the receptors for the thermoregulatory centre

A
  • In the skin
  • Receptors that measure temp of the blood
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28
Q

Changes body makes when temp is too high

A
  • Vasodilation, more blood closer to the surface so more energy is transferred from the body
  • Sweating, heat evaporates from skin so more energy is transferred from the body
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29
Q

Changes body makes when temp is too low

A
  • Sweating stops
  • Skeletal muscles contract rapidly to generate heat from respiration
  • Hairs stand on end to create insulating layer of warm air
  • Vasoconstriction means blood does not flow close to the surface, so less heat is lost
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30
Q

What is the pituitary gland

A
  • Master gland
  • Secretes hormones into the blood to either have an effect on the body or act on other glands to stimulate them to produce different hormones
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31
Q

What does the pancreas do

A
  • Secretes insulin
  • Controls blood glucose levels
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32
Q

What does the thyroid do

A
  • Secretes thyroxine
  • Controls metabolic rate, heart rate and temperature
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33
Q

What does the adrenal gland do

A
  • Secretes adrenaline
  • Involved in ‘fight or flight’ response
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34
Q

What do the ovaries do

A
  • Secretes oestrogen
  • Involved in the menstrual cycle and the development of female sexual characteristics
35
Q

What do the testes do

A
  • Secretes testosterone
  • Involved in production of sperm and development of male sexual characteristics
36
Q

Where does the blood transport hormones

A

To a target organ or tissue where it has an effect

37
Q

Why does the concentration of glucose need to be maintained

A

Needs to be kept within a certain limit because glucose is needed by cells for respiration
It is controlled by the pancreas

38
Q

What hormone does the pancreas produce if glucose levels are too high

A

Insulin

39
Q

How does insulin work

A

Binds to cells in target organs (muscles and liver) causing
1- Glucose to move from the blood into muscle cells for respiration
2 - Excess glucose to be converted into glycogen which is stored in the liver

40
Q

What hormone is produced by the pancreas if blood glucose levels decreases

A

Glucagon

41
Q

How does glucagon work

A

Binds to liver cells causing glycogen to be broken down into glucose
Glucose is released into the blood increasing the blood glucose concentration

42
Q

What is type 1 diabetes

A

When the pancreas can’t produce enough insulin.

43
Q

How is type 1 diabetes treated

A

With insulin injections at meal times, which results in glucose being taken up from the blood stream
Limit intake of simple carbs which contain lots of glucose

44
Q

What is type 2 diabetes

A

When the body cells no longer respond to insulin

45
Q

How to treat type 2 diabetes

A

Reduce number of simple carbs you intake,
Lose weight
Increase exercise
Also drugs to make insulin more effective

46
Q

What happens if concentration of water in the bloodstream increases

A
  • Cells take up water through osmosis as there’s a concentration gradient.
  • They expand and then eventually burst
47
Q

What happens if concentration of water in the bloodstream decreases

A
  • Cells lose water to the bloodstream by osmosis as there is a concentration gradient
48
Q

What happens if body cells gain or lose to much water by osmosis

A

They do not function properly

49
Q

Waste products that are processed at the kidney

A
  • Water (selectively reabsorbed)
  • Urea (all filtered out)
  • Ions (selectively reabsorbed)
50
Q

What is ADH

A
  • Anti diuretic hormone, involved in the control of the loss of water as urine
  • Released by pituitary gland
51
Q

How does ADH work

A
  • Travels via bloodstream to the kidney tubules
  • An increased amount of ADH reaching the tubules increases their permeability to water, so more water is selectively reabsorbed
  • Resulting in more concentrated urine
  • So more water goes back into the bloodstream
52
Q

Why is ADH a negative feedback loop

A

If the concentration of the blood increases/decreases, more/less ADH is secreted to reverse this change

53
Q

Two ways to treat people with kidney failure

A
  • Dialysis
  • Transplant
54
Q

Problems of dialysis

A

Possibility of blood clots
Takes up lots of time
Have to follow a strict diet
Build up of waste products between makes you feel ill

55
Q

What method of treating kidney failure is cheaper

A

Transplant

56
Q

Problems of transplant

A

Chance of rejection
Left vulnerable to disease
Do not last forever

57
Q

How can risk of rejection be decreased

A

Immunosuppressant drugs

58
Q

What is the main male reproductive hormone, what does it do.

A

Testosterone
Produced by testes
Stimulates sperm production

59
Q

What is the main female reproductive hormone, what does it do.

A

Oestrogen
Produced in ovaries
Involved in menstrual cycle

60
Q

Order of events in the menstrual cycle

A

The uterus lining breaks down, woman has period
The layer builds up until ovulation (day 14), an egg is released from the ovary, to uterus through fallopian tube
If a fertilised egg has not been embedded in the lining after 28 days, it breaks down and cycle continues

61
Q

What does FSH do

A
  • Stimulates maturation of an egg in the ovary within a follicle
  • Produced in pituitary gland
  • Stimulates ovaries to produce oestrogen
62
Q

What does oestrogen do

A

Produced in the ovaries
Secreted because of FSH
Stimulates production of LH, and inhibits the production of more FSH

63
Q

What does Luteinising Hormone do

A

Produced in pituitary gland
Produced as a result of oestrogen
Its release results in ovulation

64
Q

What does progesterone do

A

Produced in ovaries and secreted from the egg follicle
Maintains uterus lining and supports a pregnancy if the egg is fertilised
Inhibits release of FSH and LH

65
Q

What are the hormonal methods of contraception

A
  • The pill
  • Patch
  • Implant
  • Injection
  • Plastic intrauterine device
66
Q

What hormones does the contraceptive patch contain

A

Oestrogen and progesterone

67
Q

What hormones does the contraceptive implant contain

A

Continuous supply of progesterone

68
Q

What hormone does the contraceptive injection contain

A

Progesterone

69
Q

What hormone does the IUD release

A

Progesterone

70
Q

What are the non hormonal methods of contraception

A
  • Barrier methods
  • Copper IUD kills sperm
  • Removing fallopian tubes or sperm duct
  • Abstaining
71
Q

How is IVF carried out

A

Mother is given FSH and LH to encourage the maturation in eggs
These are extracted and fertilised in lab using sperm
The fertilised eggs develop into embryos and then one or two are inserted in the uterus

72
Q

What does thyroxine do

A

Regulates metabolic rate (how quickly reactions occur)
Meaning its important in growth and development

73
Q

Where is thyroxine released and how is it stimulates

A

Released by thyroid gland
Stimulated by thyroid stimulating hormone

74
Q

Describe positive phototropism

A

When plants grow towards the light source
- Plant is exposed to light on one side
- Auxin moves to shaded side
- Auxin stimulates cells to grow more here
- Meaning the shoot bends towards the light
- The plant receives more light so photosynthesis can occur at a faster rate

75
Q

Explain negative geotropism in shoots

A

Plants grow away from gravity
- If a plant is horizontal
- Auxin moves to lower side
- The cells of the shoot grow more on the side with most auxin so it stimulates cells to grow here
- The shoot will bend and grow away from the ground

76
Q

Why is negative geotropism beneficial for most shoots

A
  • Light levels are likely to be higher further away from the ground
77
Q

Explain positive geotropism in the roots

A
  • Auxin moves to lower side
  • Cells of the root grow more on the side with less auxin, so it stimulates cells to grow on the upper side
  • The root will bend and grow downwards
78
Q

Explain positive geotropism in the roots

A
  • Auxin moves to lower side
  • Cells of the root grow more on the side with less auxin, so it stimulates cells to grow on the upper side
  • The root will bend and grow downwards
79
Q

Why is positive geotropism beneficial in roots

A

Increased levels of water and nutrients lower down
It provides stability for the plant

80
Q

Why are gibberellins important

A

To stimulate seed germination

81
Q

Why is ethene important

A

For cell division, and ripening of fruits

82
Q

Why would scientists use auxin

A

Weed killers
Rooting powders
Promote growth in tissue culture

83
Q

Why would scientists use gibberellins

A

Ending seed dormancy
Promoting flowering
Increasing fruit size

Biology paper 2 (3 decks)

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