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Biology Paper 2 > B5: Homeostasis & Response > Flashcards

B5: Homeostasis & Response Flashcards

1
Q

What is homeostasis?

A

An organism’s ability to regulate/control it’s internal conditions so crucial reactions (including those involving enzymes) can happen at optimal rates.

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2
Q

What 3 things need to be regulated

A

-Blood glucose concentration
-Internal temperature
-Water levels

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3
Q

What 2 things does the nervous system consist of?

A

CNS: Central Nervous System (brain & spinal chord
PNS: Peripheral Nervous System (all other nerves)

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4
Q

What does a receptor do?

A

Detects a change due to a stimulus

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5
Q

What does a sensory neurone do?

A

Transfers a signal from a receptor to the CNS

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6
Q

What does a motor neurone do?

A

Transfers a signal from the CNS to an effector

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7
Q

What does a relay neurone do?

A

Transfers a signal from a sensory neurone to a motor neurone

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8
Q

What is the order of the reflex arc?

A

stimuli -> receptor cells -> sensory neurone -> CNS -> relay neurone -> motor neurone -> effector
signal bypasses brain

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9
Q

How do signals travel between the synapse between neurones?

A

Via neurotransmitter chemicals

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10
Q

What are glands?

A

Effectors that secrete chemicals

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11
Q

What is the practical for reaction times?

A

-Drop ruler between finger & thumb
-Measure distance fallen before caught, repeat, calculate mean
-Independent variable:
Stimulant (e.g. energy drink) increases neurotransmission
Depressant (e.g. alcohol) decreases neurotransmission
-Could use s=1/2at2 to calculate reaction time

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12
Q

What is the cerebral cortex responsible for?

A

Higher functions (conscious activities):
-Memory
-Speech
-Problem-solving

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13
Q

What is the cerebellum responsible for?

A

Motor skills:
-Movement
-Balance
-Coordination

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14
Q

What is the medulla oblongata responsible for?

A

Unconscious actions:
-Heart & breathing rate
-Signals to adrenal glands to release adrenaline

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15
Q

What are MRI scans?

A

Allow doctors to see brain activity without surgery.

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16
Q

Why is treating the brain so difficult?

A

-It is complex (difficult to physically treat without damaging it)
-Things can go wrong (e.g. tumours, trauma, mental health problems)

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17
Q

What is accommodation?

A

The eye’s ability to change the shape of the lens to focus light that comes from different distances away on the retina.

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18
Q

How does the eye focus on objects that are far away?

A

-Ciliary muscles relax
-Suspensory ligaments tighten
-Results in the lens becoming thin
-Light only refracted a little bit

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19
Q

How does the eye focus on objects that are near?

A

-Ciliary muscles contract
-Suspensory ligaments slacken
-Results in the lens becoming thick
-Light is refracted more

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20
Q

What makes the pupil change size?

A

Light intensity
-More light smaller
-Less light bigger

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21
Q

What is the cornea?

A

The transparent outer layer of the eyes
It has no blood vessels

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22
Q

What are retina cells?

A

-Rods that only detect light intensity
-Cones sensitive to red, blue or green wavelengths of light provide colour information
-These signals travel to the brain via the optic nerve

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23
Q

What is the medical term for short-sightedness?

A

Myopia

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24
Q

What is the medical term for long-sightedness?

A

Hyperopia

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25
Q

How can sight impediments be treated?

A

-Glasses
-Contact lenses
-Laser eye surgery

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26
Q

How does thermoregulation work?

A

The brain detects blood temperature then sends nervous & hormonal signals to effectors

27
Q

What happens when you are too hot?

A

-Sweat glands produce water which evaporates, taking away heat
-Blood vessels dilate: VASODILATION

28
Q

What happens when you are too cold?

A

-Hairs stand on end to trap air - layer of insulation
-Shivering - muscles produce more heat
-Blood vessels contract - VASOCONSTRICTION

29
Q

What is the endocrine system?

A

A system of glands that secrete hormones to send signals to effectors, transported via blood (slower than nervous system)

30
Q

What is the pituitary gland?

A

The ‘master’ gland: sends signals to other glands

31
Q

What does the pancreas do?

A

Secretes insulin (and glucagon) to control blood sugar

32
Q

What does the thyroid gland do?

A

Controls growth, metabolism and more

33
Q

What do the adrenal glands release?

A

Adrenaline

34
Q

What do the ovaries do?

A

-Release eggs
-Secrete hormones

35
Q

What do the testes produce?

A

Sperm

36
Q

What happens when blood glucose levels are high?

A

-Pancreas secretes insulin
-Causes glucose to move from bloodstream into cells to be used for respiration
-Excess glucose is converted into glycogen as an energy store

37
Q

What happens when blood glucose levels are low?

A

-Pancreas secretes glucagon
-Causes liver and muscles to convert glycogen back into glucose
-(This is an example of NEGATIVE FEEDBACK)

38
Q

What is type 1 diabetes?

A

-Pancreas cannot produce (enough) insulin
-Injections needed

39
Q

What is type 2 diabetes?

A

-Cells do not absorb glucose as they should
-Obesity increases risk of it developing

40
Q

What 3 processes result in water loss?

A

-Exhalation
-Sweating
-Urination

41
Q

How is excess water removed?

A

From blood by kidneys to the bladder

42
Q

What 2 things are mixed to make urine?

A

-Urea
-Water

43
Q

What does urea contain and how is it made?

A

Ammonia (NH3) from amino acids obtained from excess proteins broken down in the liver

44
Q

What would happen if the body had too much water?

A

-Water moves into cells via osmosis
-Cells become turgid, could burst

45
Q

What would happen if the body had too little water?

A

-Water moves out of cells via osmosis
-Cells become flaccid

46
Q

What is the function of the kidneys?

A

-Keep water levels just right
-Filter out glucose and useful minerals and ions for the body to use

47
Q

What is ADH and where is it produced?

A

-Anti-diuretic hormone
-Produced in the pituitary gland
-Causes tubules in kidneys to reabsorb more water into bloodstream

48
Q

What happens to ADH if water levels are too high?

A

-Less is made
-More water is sent to the bladder to leave the body as urine
-An example of NEGATIVE FEEDBACK

49
Q

What is negative feedback?

A

The response to a change is such that conditions return to normal

50
Q

What is needed if the kidneys are not working properly?

A

Dialysis:
-Blood is filtered by a machine
-If not done, ammonia/urea buildup will be poisonous

51
Q

What is the process of the menstrual cycle?

A

-Females are born with eggs, which start to mature at puberty
-FSH (follicle stimulating hormone) from pituitary gland causes an egg to mature, and the ovaries to produce
-OESTROGEN causes uterus lining to thicken, and it inhibits FSH so no more eggs mature until the next cycle. It also causes the pituitary gland to secrete
-LH (luteinising hormone) causes egg to be released, which starts to travel towards the uterus. A sperm cell can fertilise it while in the oviduct
-PROGESTERONE secreted by the ovaries maintains the uterus lining

52
Q

What are methods of contraception?

A

-FSH-inhibiting pills, no eggs mature
-Progesterone injection/implant (convenient) to stop eggs being released
-Condom/diaphragm: stops sperm meeting the egg (barrier contraception)
-IUD (copper coil): stops egg embedding in lining
-Abstinence
-Clamping oviduct or vasectomy (cutting sperm tubes)

53
Q

What are examples of fertility treatments?

A

-FSH/LH injections
-IVF (in-vitro fertilisation)

54
Q

How does IVF work?

A

-Eggs collected after inducing release with LH to be fertilised in an lab
-Viable embryos inserted back into woman’s uterus

55
Q

What are cons of IVF?

A

-It’s hard
-Expensive
-There is a low success rate
-Can potentially cause multiple embryos to develop

56
Q

What does adrenaline do?

A

Increases blood flow & breathing rate, to prepare you for ‘fight or flight’

57
Q

What does thyroxine control?

A

The body’s metabolic rate

58
Q

What happens when thyroxine levels are too low?

A

-Hypothalamus in brain releases TRH
-Causes pituitary gland to release TSH
-Causes thyroid to release more thyroxine
- Example of NEGATIVE FEEDBACK

59
Q

What do gibberellins do?

A

-Induce germination
-Promote flowering
-Increase fruit size

60
Q

What does ethene do?

A

-Cause ripening

61
Q

What do auxins control and how do they work?

A

-Shoot and root growth
-Sunlight destroys it, so causes the cells on the shaded side of the shoot to grow/elongate more quickly
-Shoot bends towards the sun (PHOTOTROPISM)
-Gathers on bottom of roots, where it inhibits growth instead, meaning it grows downward (GEOTROPISM)

62
Q

What are 3 things auxins be used as?

A

-Weedkillers
-Rooting powders
-Promoting growth in tissue cultures

63
Q

What is the practical to observe geotropism in roots?

A

-Place seeds on damp cotton wool in petri dish stood on edge
-Turn 90 degrees after a few days to observe geotropism in roots

Biology Paper 2 (3 decks)

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