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AQA GCSE - Biology - paper 2 > Homeostasis & response > Flashcards

Homeostasis & response Flashcards

1
Q

What is homeostasis?


A

Homeostasis is the process of maintaining a stable internal environment in the body.

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2
Q

Why do cells in the body need certain conditions to function properly?


A

Cells and enzymes need specific conditions to function properly, such as temperature and pH levels.

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3
Q

What are some conditions that cells cannot tolerate?


A

Cells cannot tolerate extreme temperatures or pH levels that are too acidic or too alkaline.

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4
Q

How does the body regulate internal conditions?


A

The body regulates internal conditions by maintaining levels of glucose, water, and temperature around the right levels.

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5
Q

What does the term ‘fluctuate’ mean in the context of homeostasis?


A

‘Fluctuate’ means that certain levels, like temperature and glucose, can vary but remain within small bounds.

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6
Q

What is the definition of homeostasis?

A

Homeostasis is the regulation of conditions inside the body to maintain a stable internal environment in response to changes.

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7
Q

How does the body maintain internal conditions despite external changes?


A

The body maintains internal conditions by using automatic control systems that respond to changes in both internal and external environments.

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8
Q

What are the three main components of automatic control systems in the body?


A

receptors, coordination centers, and effectors.

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9
Q

What role do receptors play in homeostasis?


A

Receptors detect changes in the environment, such as a rise in temperature.

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10
Q

What is the function of coordination centres in the body?


A

Coordination centers, like the brain or spinal cord, interpret changes detected by receptors and decide on the necessary response.

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11
Q

What are effectors in the context of homeostasis?


A

Effectors are the components that carry out the response to changes, such as muscles contracting or glands releasing hormones.

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12
Q

How do the nervous and endocrine systems communicate in homeostasis?


A

The nervous system sends fast electrical impulses, while the endocrine system relies on hormones released into the bloodstream

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13
Q

What is the difference between the nervous system and the endocrine system in terms of response speed?


A

The nervous system responds quickly, while the endocrine system is generally slower and longer-lasting.

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14
Q

What is negative feedback in the context of homeostasis?


A

Negative feedback is a mechanism that decreases a level when it gets too high and increases it when it gets too low.

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15
Q

How does negative feedback work when glucose levels are too high?

A

Negative feedback decreases glucose levels back to normal when they are too high.

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16
Q

What happens if glucose levels decrease too much?


A

If glucose levels decrease too much, negative feedback will increase them back to normal.

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17
Q

What is the process of maintaining a stable internal environment called, and how does it work?


A

The process is called homeostasis.
It involves:
1. Detection of changes by receptors.
2. Interpretation of changes by coordination centers.
3. Response by effectors to restore balance.

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18
Q

What happens when the body enters a cold environment?


A

Receptors detect low temperature, and the nervous system sends signals to effectors like muscles to initiate shivering, raising body temperature.

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19
Q

describe the different parts of the nervous system:

A

1) Central nervous system - consists of the brain and spinal cord, connected to the rest of the body
2) Sensory neurones - the neurones that carry information as electrical impulses from the receptors to the CNS
3) Motor neurones - the neurones that carry electrical impulses from the CNS to effectors
4) Effectors - all muscles and glands that respond to nervous impulses

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20
Q

What does the CNS do? (in detail)

A

The CNS is a coordination centre - it recieves information from the receptors and then coordinates a response (decides what to do). The response is carried out by effectors.

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21
Q

What are synapses?

A

The connection between two neurones is called a synapse. The nerve signal is transferred by chemicals which diffuse (move) across the gap. These chemicals then set off a new electrical signal in the next neurone.

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22
Q

Describe the process of a reflex in the human body:

A

1) The neurones in reflex arcs go through the spinal cord or through an unconscious part of the brain
2) When a stimulus is detected by receptors, impulses are sent along the sensory neurone to a relay neurone in the CNS
3) When the impulses reach a synapse between the sensory neurone and the relay neurone, they trigger chemicals to be released
4) When the impulses reach a synapse the same thing happens. Chemicals are released and cause impulses to be sent along the motor neurone
5) The impulses travel along the motor neurone to the effector
6) the effector then moves to respond to the initial stimulus
7) Because you do not have to think about it, the response is quicker

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23
Q

What are reflexes and why do we have them?

A

Reflexes are rapid, automatic responses to a certain stimulus. They do not involve the conscious part of the brain. They prevent injury. The passage of information in a reflex (from receptor to effector) is called a reflex arc

24
Q

what are the four parts of the brain and their function:

A

1 - cerebral cortex - controls your consciousness, intelligence, memory and language
2 - medulla - controls unconscious activities like breathing
3 - cerebellum - responsible for muscle coordination
4 - spinal cord - other part of CNS

25
Q

How do scientists study the brain?

A
  • studying patients with brain damage to see the effect
  • electrically stimulating the brain to see reaction
  • MRI scans to see images of the brain
26
Q

What are the key parts of the eye and their function?

A

1) Sclera - tough, supporting wall of the eye
2) Cornea - transparent outer layer. Refracts light into eye
3) Iris - contains muscles which control the size of pupil
4) Lens - focusses light onto the retina
5) Optic nerve - carries impulses
6) Ciliary muscles & Suspensory ligaments - control shape of lens

27
Q

What happens if a bright light is shone at your eye?

A

The light receptors in the eye detect a bright light. The circular muscles in the iris contract and the radial muscles relax. This reduces the amount of light entering the eye

28
Q

What happens if you’re eye is in darkness?

A

The light receptors in the eye detect the lack of light. The radial muscles contract and the circular muscles in the iris relax.

29
Q

How does your eye look at a near object?

A
  • the ciliary muscles contract, so the suspensory ligaments slacken
  • the lens becomes fat (more curved)
  • this increases the amount by which it refracts light
30
Q

How does your eye look at a distant object?

A
  • the ciliary muscles relax, which pulls the suspensory ligaments tight
  • This makes the lens go thin (less curved)
  • This reduces the amount of light refracted
31
Q

Describe being long vs short sighted:

A

Long sighted / hyperopia:
- cannot focus on near objects
- happens when light isn’t refracted enough or the eyeball is too short
- the images are brought into focus behind the retina
- fixed with a convex lens
Short sighted / myopia:
- cannot focus on distant objects
- happens when light is refracted too much or the eyeball is too long
- the images are brought into focus in front of the retina
- fixed with a concave lens

32
Q

What are the three main treatments for vision defects (excluding wearing glasses) ?

A
  • contact lenses
  • laser eye surgery
  • replacement lens surgery
33
Q

what is the endocrine system made up of?

A

All the glands that release hormones (endocrine glands):
- pituitary glands - many hormones
- thyroid - thyroxine
- adrenal gland - adrenaline
- pancreas - insulin
- ovaries (female) - oestrogen
- testes (male) - testosterone

34
Q

what does each hormone do?
Include what the pituitary gland does.

A

1) Pituitary gland - uses hormones to direct other glands to release hormones
2) Thyroxine - regulates metabolism, heart rate and temperature
3) Adrenaline - prepares body for flight or fight response
4) Insulin - regulates the blood glucose level
5) Oestrogen - involved in the menstrual cycle
6) Testosterone - controls puberty and sperm production

35
Q

What happens when the blood glucose level is too high?

A
  • insulin secreted by pancreas
  • glucose is moved from blood into liver and muscle cells
  • blood glucose returns to optimum level
36
Q

What happens when the blood glucose level is too low?

A
  • glucagon secreted by pancreas
  • glucose released into blood by liver
  • blood glucose returns to optimum level
37
Q

What are the two types of diabetes?

A

type 1 - pancreas produces little or no insulin. This means glucose levels can rise to a fatal level. The person usually has to have several injections of insulin throughout the day
type 2 - a person becomes resistant to their insulin (body still produces it). The person can control this by eating a controlled diet and regular treatment.

TYPE 1 CANNOT BE CURED, TYPE 2 CAN BE CURED.

38
Q

What do kidneys do? What processes do they carry out?

A

They make urine by taking waste products (and unwanted substances) out of the blood.
1) Filtration - filters out substances as it passes through the kidneys
2) selective reabsorption - useful substances are reabsorbed into the blood in to maintain the right amount

39
Q

What substances are removed?

A

1) Urea - Proteins cannot be stored in excess so they are converted into fats and carbohydrates, which can be stored (deamination) A waste product is Ammonia which is toxic. It is converted to urea and filtered out
2) Ions - ions like sodium are taken into the body in food and absorbed into the blood. If the ion content of the body is wrong, it affects the balance so some ions are lost in sweat, and the kidneys maintains the balance. Any waste ions are removed in urine
3) Water - the body has to constantly balance the water levels. We lose it when breathing and sweating, so the kidneys balance the remaining water levels. Any excess is removed in urine

40
Q

What does the anti-diuretic hormone (ADH) do?

A

This hormone is used to balance the concentration of urine. The brain monitors the water level constantly, releasing this hormone which triggers the kidneys to absorb more/less water.

41
Q

What are the two types of treatment for kidney failure?

A

1) Dialysis machine - the dialysis fluid contains the same amount of glucose and salts so that they do not move between the blood and fluid, but contains no urea. This means the urea in the blood diffuses out, so that the clean blood is left in the body
2) Kidney transplant - this is when a patient has their kidney removed, and a donor kidney replaces it. This means that they have a working kidney, but it could be rejected. A kidney transplant is the ONLY cure for kidney failure.

42
Q

What happens in each of the four stages of the menstrual cycle?

A

(stage 1) - Day 1 - menstruation starts. The uterus lining breaks down for around 4 days.
(stage 2) - Day 4 to 14 - the uterus lining builds back up again into a thick spongey layer full of blood vessels, ready to receive a fertilised egg.
(stage 3) - Day 14 - an egg develops and is released from the ovary, Ovulation.
(stage 4) - Day 14 - 28 - the wall is maintained. If no fertilised egg has landed on the wall, the lining breaks down and the cycle restarts.

43
Q

What hormone controls each stage of the menstrual cycle?

A

1 - FSH (Follicle Stimulating hormone) - causes an egg to mature in a structure called a follicle. Stimulates the ovaries to produce oestrogen
2 - Oestrogen - causes the lining of the uterus to grow. Stimulates the release of LH and inhibits (prevents) the release of FSH
3 - LH (Luteinising Hormone) - stimulates the release of an egg at day 14 (ovulation)
4 - Progesterone - maintains the lining of the uterus during the second half of the cycle. When its level falls, the lining breaks down. Inhibits the release of LH and FSH

44
Q

Give an example of using hormones to reduce fertility:

A
  • Taking the pill (a combination of oestrogen and progesterone) every day
  • Taking the progesterone pill every day
  • Having the contraceptive patch each week
  • Having the contraceptive implant
  • Having the contraceptive injections
  • Having an intrauterine device (IUD) - either plastic or copper
45
Q

give an example of a barrier method to prevent pregnancy:

A
  • Condoms
  • A diaphragm (must be used with spermicide)
  • Spermicide
46
Q

Give an advantage and disadvantage of using hormones to increase fertility:

A

A - helps women to be pregnant when they previously couldn’t
D - may not work so it can be expensive if done multiple times
D - too many eggs could be stimulated, resulting in unexpected multiple pregnancies

47
Q

How does IVF work? (5 stages)

A

1 - IVF involves collecting eggs from the woman’s ovaries and fertilising them in a lab
2 - IVF may also involve the sperm being injected directly into the egg
3 - the fertilised eggs are then grown into embryos in a laboratory incubator
4 - once the embryos are tiny balls of cells, one or two are transferred to the woman’s uterus to improve the chance of pregnancy.
5 - FSH and LH are given before egg collection to stimulate several eggs to mature

48
Q

What are the pros and cons of IVF?

A

P - allows an infertile couple to have a child
C - can be emotionally and physically stressful
C - multiple births can happen (could be dangerous to mother and babies as there is a higher risk of stillbirth, miscarriages…)
C - the success rate of IVF is low (around 26%)

49
Q

What is adrenaline?

A

It is a hormone released by the adrenal glands, which is released in response to stressful or scary situations. It gets the body ready for a fight / flight response. The body increases the supply of oxygen and glucose to the brain and muscles.

50
Q

What is thyroxine?

A

A hormone released by the thyroid gland, it regulates the basal metabolic rate (the speed that chemical reactions in the body whilst resting

51
Q

Describe the role of auxin in plant shoots and roots:

A

Auxin is a hormone in the tips of shoots and roots. It controls the way the plant grows in response to light (phototropism) and gravity (gravitropism & geotropism)

52
Q

Why do plants grow towards light?

A

1 - when the plant is exposed to light, more auxin collects on the side in the shade than the side in the light
2 - This makes the cells elongate (grow) faster on the shaded side so the shoot bends towards light

53
Q

Why do plant shoots grow away from gravity but the roots grow towards gravity?

A

1 - When a shoot grows sideways, gravity produces an unequal distribution of auxin, with more on the lower side
2 - This causes the lower side to grow faster, bending the shoot upwards
3 - A root growing sideways will always have more auxin on the lower side
4 - But in a root the extra auxin inhibits (prevents) growth. This means the cells on top grow faster, and the root bends downwards.

54
Q

What can the plant hormone auxin be extracted and used for?

A
  • killing weeds
  • growing from cutting with rooting powder
  • growing cells in tissue culture
55
Q

What is gibberellin used for in plants and what is it extracted for?

A
  • Gibberellin stimulates seed germination, stem growth and flowering
  • It can be used for: Controlling dormancy, inducing flowering, and growing larger fruit
56
Q

What does the gas ethene do in plants and how do we use it?

A
  • Ethene influences the growth of the plant by controlling cell division.
  • We use it to ripen fruit whilst transported between the farm (unripe) and the supermarket (ripened)

AQA GCSE - Biology - paper 2 (3 decks)

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