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B5 homeostasis and response Flashcards

1
Q

Describe how the nervous system coordinates a reflex action when touching a hot object

A

Receptor cells in the skin detect a stimuli, creating an impulse to pass along neurones. Impulses pass from sensory to relay to motor neurones. There are synapses between neurones where chemicals known as neurotransmitters diffuse over. Motor neurones carry impulse to the muscles (effectors) contract to quickly pull the hand away from the hot object.

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2
Q

What are 3 differences between the endocrine and nervous system?

A
  1. Endocrines coordination is slower
  2. Endocrines coordination lasts longer
  3. Hormones in the endocrine system travel through blood not by impulses
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3
Q

How can MRI scanners that allow a patient with brain damage to move help neuroscientists learn more about the brain?

A

Make patient do an activity ie read a book to see which part of the brain is active in patients to see where the damage is by comparing with someone that has no brain damage.

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4
Q

Describe how the brain receives information about light entering the eye

A

The retina has light sensitive receptor cells that create an impulse. The impulse passes along the sensory neurone and along the optic nerve where the impulse goes to the brain to process the image.

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5
Q

RPA 7: how do you improve accuracy? (4)

A
  1. drop ruler from same height
  2. measure the same distance between thumb and forefinger
  3. use a computer (records to miliseconds)
  4. Use a ruler with a more precise scale with a higher resolution ie mm
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6
Q

RPA 7: 2 factors affecting reaction time?

A
  • Age
  • Caffeine
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7
Q

RPA 7: explain the effect of increasing caffeine on reaction time.

A

As volume of caffeine increases reaction time increases

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8
Q

RPA 7: explain why there may be a negative result.

A

The person’s reaction time was greater (took longer)

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9
Q

RPA 7: explain why it is not a reflex pathway.

A

It is not an automatic response as it uses the conscious part of the brain.

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10
Q

RPA 7: what is the advantage of using a computer?

A
  • More accurate as avoids predicting when person will drop the ruler (random error)
  • More precise as higher resolution (to milliseconds)
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11
Q

How does a persons eye adjust to see a nearer object?

A

The ciliary muscles contract (inwards) so they have a smaller diameter
The suspensory ligaments loosen
The lens is then thicker and so light rays refract more strongly so image focuses on the retina

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12
Q

Explain why long sighted people struggle to see near objects.

A

They have hyperopia so the lens cannot be thickened enough and so is too flat. Therefore light does not refract enough so light focuses behind the retina.

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13
Q

Describe how structures conduct a reflex action.

A

Receptor detects a stimuli and generates an impulse to be carried along neurones. Impulses are carried along sensory neurones to relay neurones to motor neurones. There are synapses (small gaps between neurones) which chemicals called neurotransmitters diffuse over and bind to receptors to stimulate impulses in the next neurone. Impulses travel along the motor neurone to the effector which carries out the response, ie - a muscle contracting.

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14
Q

What short sightedness and how is it corrected?

A

Myopia is when light doesn’t focus on the retina but in front of it as the lens is too thick/curved and can’t be made thin enough so light refracts too much. It is corrected by using a concave lens which refracts light less as light rays are bent outwards so that the image focuses on the retina.

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15
Q

What is a synapse?

A

A small gap between neurones at each junction

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16
Q

What are neurotransmitters?

A

Chemicals which are released at the end of a neurone and diffuse across a synapse, binding to (receptors on) the next neurone to carry on an electrical impulse

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17
Q

Explain the iris reflex in bright light.

A

The pupil constricts. This is due to circular muscles contracting (towards its centre) and radial muscles relaxing. Therefore less light enters the eye, avoiding eye damage.

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18
Q

Explain why the brain cools when cold water is drank.

A

Blood is cooled at the mouth so cooled blood flows to the brain

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19
Q

How does the body respond to a decrease in temperature?

A
  • TC has temperature receptors that detect change in blood (and so body) temperature
  • Blood vessels constrict (vasoconstriction) where blood flows closer to the core and is the skins blood supply is shut off so less energy is lost to the surroundings (by radiation)
  • Person stops sweating so less heat lost as evaporation
  • Person shivers by rapid muscle contraction, releasing heat energy from the respiration for warmth
    This warms the blood which warms the body
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20
Q

How does the body respond to an increase in body temperature?

A
  • Vasodilation - blood vessels dilate and blood flows to the surface of the skin so more heat is lost by radiation
  • Sweating to lose heat by evaporation
  • Cools the blood, which cools the body
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21
Q

How does vasodilation work in decreasing body temperature?

A

Blood vessels dilate so blood flows to the surface of the skin so more (heat) energy is lost by radiation to the surroundings which cools the blood which cools the body.

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22
Q

What does the thermoregulatory system and skin have receptors sensitive to?

A
  • Temperature of the blood
  • Skin has receptors sensitive to temperature of skin and sends nervous impulses to the thermoregulatory centre
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23
Q

How does a person focus on a distant object?

A

The ciliary muscles relax outwards to have a larger diameter
The suspensory ligaments are pulled tight/taut
The lens is then pulled thin and only slightly refracts light rays and image focusses on the retina

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24
Q

How does the body respond to a decrease in blood glucose concentration?

A

Pancreas detects low level glucose and releases glucagon into the blood. Stimulates glycogen (in the liver and muscle cells) to convert to glucose and be released into the blood until level is restored until blood glucose too high and insulin will begin to be released (negative feedback system)

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25
How does the body respond to an increase in blood glucose concentration?
Pancreas detects high levels of glucose and releases the hormone insulin that causes glucose to move /diffuse from the blood into the muscle cells and liver where excess glucose is converted to glycogen for storage until blood glucose levels too low and glucagon will begin to be released.
26
Why does an enzyme that converts fats to glucose not working in the liver cause death in starving children?
Starving children have used up their glycogen stores so would need the liver enzyme to release glucose from fats. As the enzyme doesn't work, less/no glucose is released so respiration is insufficient
27
Why does an enzyme that converts fats to glucose work in the liver prevent death in non-starving children?
Have glycogen in the liver so glucagon will continue to stimulate the release of glucose into the blood so respiration is sufficient.
28
Describe how hormones control the menstrual cycle and where they come from
- FSH (from pituitary gland) stimulate egg maturation and oestrogen production - Oestrogen (from ovaries) inhibit FSH, builds and maintains uterus lining and stimulates LH production - LH (from pituitary gland) inhibits oestrogen and stimulates ovulation and progesterone production - Progesterone (from ovaries) inhibits FSH and LH and builds and maintains uterus lining
29
What are 3 advantages of kidney transplants over dialysis?
- No risk of infection from frequent needle puncturing skin (but may be infected due to suppression drugs) - Maintains correct concentration of substances (ie no build up of toxic urea so no cell damage) - No need for regular hospital visits so less time consuming
30
What are 3 disadvantages of kidney transplants over dialysis?
- Risk of rejection, have to take anti-rejection drugs (immunosuppressants) - Risk of infection during surgery and from anti-rejection drugs which suppress immune system - Shortage of donors
31
Explain how the pituitary gland and kidneys reduce water loss.
- Low water levels detected by pituitary gland so releases more ADH - ADH stimulates kidney tubules to become more permeable so more water is reabsorbed into the blood and a lower volume of water in urine - Controlled by negative feedback
32
What happens to cells if a person doesn't urinate?
Cells swell and burst as too much water moves in by osmosis so cell membrane can't withstand the high pressure -> cell damage so cells and so body don't function properly
33
Give two advantages of using condoms.
- Prevents STIs/STDs - Doesn't cause any side effects
34
What would happen to insulin in the stomach?
Would be broken down by (hydrochloric) acid (as its a protein)
35
Explain why more water is lost through the skin during a race.
More sweating as exercise releases heat (from respiration) so body must be cooled by evaporation.
36
Explain why more water is lost through breathing during a race.
More energy needed (by muscles) so more aerobic respiration so breathing rate increases to supply oxygen.
37
Why does a persons urine contain a higher concentration of urea and mineral ions on a hot day when exercising?
Sweat more to cool down so more water lost. Pituitary gland detects low levels of water and releases ADH so more water is reabsorbed in the blood as kidney tubules become more permeable. Therefore, less water in urine (so concentration of urea and ions appears higher)
38
Why may body temperature increase?
Increased respiration for muscle contraction so more energy released (as heat)
39
Explain why urine contains mineral ions and urea, but no glucose or protein
- mineral ions are filtered and some are reabsorbed - urea is filtered and almost none is reabsorbed - protein is not filtered (too large to pass through filter) - glucose is filtered and completely reabsorbed
40
Why do runners drink sports drinks during a race?
Replace ions and water lost in sweat + glucose for respiration.
41
Describe how the oral contraceptive pill prevents a woman becoming pregnant.
Progesterone inhibits FSH and LH which prevents maturation of the egg and ovulation.
42
Explain what happens to the glucose in the blood of a healthy person when blood enters the kidney.
Glucose is filtered and is all of it is completely reabsorbed.
43
Explain why urea and ions are found In urine and why they have a higher concentration on hotter days.
- Not all ions + urea are **reabsorbed** to maintain the right balance of substance levels, excess are removed - Most of urea is excreted in urine as it is toxic waste which is harmful if builds up - More water is reabsorbed on a hot day due to more water lost from sweating so water volume in urine is lower therefore concentration of urea and ions appears higher
44
Why may a body overheat on humid days?
Sweat is released but cannot evaporate due to high moisture concentration in the air so less heat loss as it is evaporation that cools the body
45
What is a hormone?
A chemical messenger secreted by an endocrine gland (when detecting a stimulus) which targets specific organs when released into the blood.
46
Explain how the process of kidney dialysis works
Skin punctured and blood flows into dialysis machine, partially permeable membrane with dialysis fluid containing a lower concentration of water and urea but the same concentration of glucose (all of glucose is reabsorbed) Water, urea and salts (ions) are filtered through the dialysis machine, diffusing across membrane Other molecules are too large to be filtered
47
Suggest why the urine of a diabetic person may contain glucose.
Too much glucose is in the bloodstream so the kidneys can’t filter and reabsorb it quick enough.
48
Suggest the effects of an overactive thyroid gland.
- Too much thyroxine released into the blood so raises BMR levels which increase rate of respiration - As a result could lead to fatigue and overheating and weight loss (energy released and lost at a very fast rate)
49
What is the purpose of thyroxine?
Stimulates the basal metabolic rate. It plays an important role in growth and development (for protein synthesis). Levels are controlled by negative feedback in response to TSH released from the pituitary gland.
50
What is the purpose of adrenaline?
It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for ‘flight or fight’ response
51
Give 2 factors that can affect metabolic rate.
1. age 2. hormone balance (thyroxine)
52
Explain why a contraceptive pill with a dip in progesterone levels is less effective.
FSH and LH no longer inhibited (as effectively) so an egg (more likely) matures and is released (ovulates).
53
Explain why there is a risk of rejecting with transplants.
White blood cells/ immune system detect foreign cells so produce antibodies which attack the organ's antigens.
54
What is ovulation?
At puberty eggs begin to mature and one is released approximately every 28 days (stimulated by LH hormone)
55
Explain the process of IVF
- Giving a mother FSH and LH to stimulate the maturation of several eggs. - Mature eggs are collected from the mother and fertilised by sperm from the father in the laboratory. - The fertilised eggs develop into embryos - One or two embryos are inserted into the mother’s uterus
56
Why do plants release hormones?
To coordinate and control growth and responses to light (phototropism) and gravity (gravitropism or geotropism)
57
Give two factors seedlings compete for.
- Light - Water
58
Explain how phototropism in a plant helps it survive.
More light as shoot grows towards the light so more photosynthesis. Therefore more glucose so more proteins made for growth.
59
How would you measure a bent shoot?
Straighten the shoot and measure with a ruler.
60
Describe the effect of auxin in the roots and compare its distribution.
Auxin inhibits growth in the roots. - If more concentrated at the bottom (due to gravity) then there is an uneven distribution of the plant hormone and top side grows faster than bottom side so a positive geotropism (in the direction of gravity) - If even distribution then grow equally.
61
Suggest an advantage of soaking seeds in gibberellins in the cold seasons.
Germinate sooner so growing season is longer (ending seed dormancy)
62
RPA 8: how would you carry out?
- 10 cress seeds into 3 separate Petri dishes and incubate to germinate - measure initial height with a ruler - place in different conditions; full sunlight, partial light and complete darkness - measure height each day for a week by straightening shoots and measuring with a ruler then calculate a mean - plot a graph of growth against time - compare height for each light intensity -> ie complete darkness will be the highest
63
RPA 8: why are the shoots in darkness the longest and yellow?
- They are trying to reach for light so that they can photosynthesise and produce glucose for growth - Chlorophyll (green pigment) deteriorates in no light so no longer present
64
Explain the uses of auxins.
Weed killer: in broad leaves as make them grow too much but reduces biodiversity Rooting powder: quick method to produce clones of a plant Tissue culture: help stimulate quick growth
65
Explain the uses of gibberellins.
End seed dormancy: germinate sooner at a time they normally wouldn't so growing season is longer Flowering: regardless of weather and grow bigger Larger fruit: often seedless
66
Explain the use of ethene.
Ethene is used in the food industry to control ripening of fruit during storage and transport
67
How does auxin control the response of a plant where light is shining on one side?
Auxin comes from the tip (of the shoot) and concentrates on the shaded side with less light so stimulates (unequal) growth due to unequal distribution of plant hormone. Shaded side grows more than lighter side so shoot grows towards light.
68
What does low temperature mean for a hibernating animal?
Less energy lost so energy stores last longer (won't die of starvation).
69
Why do organisms have a high temperate when they are active?
When an organism is active it must be moving and this requires energy from respiration. This process releases heat which increases enzyme activity.
70
What are plant growth hormones used for?
Agriculture Horticulture
71
How does the everyday use of hormones as weed killers have an effect on biodiversity?
Selective weedkillers kill plants that some species of animals rely on as a food source. This can result in a reduction of biodiversity.
72
Describe the function of receptors in the skin
Detect stimuli and convert information to electrical impulses, which are carried along sensory neurones in response to skin temperature
73
Explain why it is important to control body temperature
Optimal conditions for enzymes to work best, preventing them from denaturing
74
What is the issue with multiple births?
Risk of harm to mother during birth, for example a miscarriage
75
Describe what happens to amino acids that cannot be stored in the body
Amino acids are broken down in the liver (into carbohydrates+fats and waste ammonia which is toxic so it is then) converted into urea). This process is called deamination. The urea is then filtered through the kidneys and stored in bladder.
76
Explain two biological reasons why kidney transplants are better than dialysis
- not constantly puncturing skin so less risk of infection - changes in concentrations.levels of urea are minimised, so less chance of causing damage to body cells
77
Explain why a person with type 2 diabetes has a high insulin concentration
Cells absorb less glucose and convert it less to glycogen as no longer respond to insulin so blood glucose concentration remains high. This stimulates pancreas to release more insulin
78
Describe menstrual cycle
- menstruation - new egg matures (due to FSH) and uterus lining builds up (due to oestrogen) - ovulation (due to LH) - maintained uterus lining (by progesterone) if fertilised maintained if not fertilised cycle repeats
79
Explain the effect of insulin
Stimulates glucose to move out of blood and be taken in by liver and muscle cells where it is converted by them to glycogen
80
How are auxins used in weedkillers?
Stimulates too much growth Disrupts growth process and so kills the plant

Biology 2 (3 decks)

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