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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 conditions inside your body (and cells) to maintain a stable internal environment, in response to changes in both internal and external conditions

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2
Q

what are the three main components that make up your automatic control systems

A

-receptors
-coordination centre
- effectors

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3
Q

what does negative feedback do

A

it counteracts changes to keep your internal environment stable

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4
Q

how does negative feedback work

A

1) receptor detects a stimulus - level is too high/low
2) the coordination centre receives and processes the information, then organises a response
3) effector produces a response, which counteracts the change and restores the optimum level - the level increases/decreases

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5
Q

what does the nervous system do

A

detect & react to stimuli

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6
Q

what is the nervous system made up of

A
  • central nervous system (CNS)
  • sensory neurones
  • motor neurones
  • effectors
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7
Q

what is the CNS

A

a coordination centre. in vetebrates (animals with backbones) this consists of the brain & spinal cord only. in mammals, the CNS is connected to the body by sensory neurones & motor neurones

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8
Q

what are sensory neurones

A

the neurones that carry information as electrical impulses from the receptors to the CNS

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9
Q

what are motor neurones

A

the neurones that carry electrical impulses from the CNS to effectors

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10
Q

what are effectors

A

all your muscles & glands, which produce a response to nervous impulses

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11
Q

what are receptors

A

cells that detect stimuli

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12
Q

what does the CNS do

A

it receives information from the receptors and then coordinates a response which is carried out by effectors

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13
Q

what is a synapse

A

the connection between two neurones. the nerve signal is transferred by chemicals which diffuse across the gap. these chemicals then set off a new electrical signal in the next neurone

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14
Q

what are reflexes

A

reflexes are rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain - they reduce the chances of being injured

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15
Q

what is a reflex arc

A

the passage of information in a reflex (from receptor to effector)

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16
Q

how does the reflex arc work

A

1) the neurones in the reflex arc 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 a 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. these chemicals cause impulses to be sent along the relay neurone
4) when the impulses reach a synapse between the relay neurone and a motor neurone, chemicals are released and cause impulses to be sent along the motor neurone
5) the impulses travel along the motor neurone to the effector (usually muscle)
6) the muscle then contracts and moves away from the stimulus

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17
Q

what is your reaction time

A

the time taken to respond to a stimulus. this can be affected by factors such as age, gender, or drugs

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18
Q

how do you measure the effect of caffeine on reaction time

A

1) the person being tested should sit with their arm resting on the edge of a table (stop them from moving their arm up/down during the test)
2) hold a ruler vertically between their thumb and forefinger. make sure that the zero end of the ruler is level with their thumb and finger. then let go without giving any warning
3) the person being tested should try to catch the ruler as quickly as they can
4) reaction time is measured by the number on the ruler when it’s caught. the number should be read from the top of the thumb. the further down the ruler it’s caught, slower their reaction time
5) the person being tested should then have a caffeinated drink (e.g. 300ml of cola). after 10 mins, repeat steps 1-5

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19
Q

how can reaction time be measured using a computer

A

the person being tested has to click the mouse (or press a key) as soon as they see a stimulus on the screen, e.g. a box change colour

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20
Q

how are computers scientifically better at measuring reaction time

A
  • computers can give more precise reaction time because they remove the possibility of human error from the measurement
  • as the computer can record the reaction time in milliseconds, it can also give a more accurate measurement
  • using a computer can also remove the possibility that the person can predict when to respond - using the ruler test, the catcher may learn to anticipate the drop by reading the tester’s body language
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21
Q

what are hormones

A

chemical molecules released directly into the blood

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22
Q

what is the pituitary gland

A

the pituitary gland produces many hormones that regulate body conditions. it is sometimes called the ‘master gland’ because these hormones act in other glands, directing them to release hormones that bring about change

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23
Q

what is the thyroid gland

A

this produces thyroxine, which is involved in regulating things like the rate of metabolism, heart rate and temperature

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24
Q

what is the adrenal gland

A

this produces adrenaline, which is used to prepare the body for a ‘fight or flight’ respinse

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25
what is the pancreas
this produces insulin, which is used to regulate the blood glucose level
26
what are the ovaries
produces oestrogen, which is involved in the menstrual cycle. only found in females
27
what are the testes
produces testosterone, which controls puberty and sperm production in males
28
what are the differences between hormones and nerves
nerves: - very fast action - act for a very short time - act on a very precise area hormones: - slower action - act for a long time - act in a more general way
29
what 2 hormones control blood glucose levels
insulin & glucagon
30
what is excess glucose stored as and where is it stored
excess glucose is stored as glycogen and is stored in the liver and muscles
31
what happens when blood glucose levels get too high
insulin is secreted by the pancreas. the insulin binds to receptors on liver & muscle cells which tells the cells to take some of the glucose floating in the blood. the liver & muscle cells take up lots of extra glucose molecules and liver cells turn glucose into glycogen (storage form of glucose). this decreased the blood glucose.
32
what happens when blood glucose levels get too low
glucagon is secreted from the pancreas and binds to liver cells which break the glycogen down into glucose. this glucose is released into the blood increasing the blood glucose levels
33
what is diabetes
a condition that affects your ability to control your blood sugar level
34
what is type 1 diabetes
when the pancreas produces little to no insulin
35
what is insulin therapy
insulin therapy involves several injections of insulin throughout the day, mostly at meal times. this makes sure the glucose is removed from the blood quickly once the food has been digested, stopping the level getting too high. the amount of insulin injected depends on the person’s diet & how active they are
36
what else can be done for type 1 diabetes besides insulin therapy
the person should limit the intake of foods rich in simple carbohydrates and do regular exercise
37
what is type 2 diabetes
where the person becomes resistant to their own insulin (they still produce insulin, but their body’s cells don’t respond properly to the hormone). this can cause a person’s blood sugar level to rise to a dangerous level
38
what is a risk factor of type 2 diabetes
obesity
39
how is type 2 diabetes controlled
by eating a carbohydrate-controlled diet and getting regular exercise
40
what is the main reproductive hormone in men and what does it do
the main reproductive hormone is testosterone which is produced by the testes and stimulates sperm production
41
what is the main reproductive hormone in women and what does it do
the main reproductive hormone is oestrogen which is produced in the ovaries. as well as bringing about physical changes, oestrogen is also involved in the menstrual cycle
42
what happens in stage 1 of the menstrual cycle
menstruation starts and the uterus lining breaks down for about 4 days
43
what happens in stage 2 of the menstrual cycle
the uterus lining builds up again, from day 4 to day 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg
44
what happens in stage 3 of the menstrual cycle
an egg develops and is released from the ovary at day 14 (ovulation)
45
what happens in stage 4 of the menstrual cycle
the wall is then maintained for about 14 days until day 28. if no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down and the whole cycle starts again
46
what is FSH and what does it do
- follicle-stimulating hormone - produced in the pituitary gland - causes an egg to mature in one of the ovaries, in a structure called a follicle - stimulates the ovaries to produce oestrogen
47
what is oestrogen and what does it do
- hormone produced in the ovaries - causes the lining of the uterus to grow - stimulates the release of LH (which causes the release of an egg) and inhibits release of FSH
48
what is LH and what does it do
- luteinising hormone - produced by the pituitary gland - stimulates the release of an egg at day 14 (ovulation)
49
what is progesterone and what does it do
- hormone produced in the ovaries by the remains of the follicle after ovulation - maintains the lining of the uterus during the second half of the cycle. when the level of progesterone falls, the lining breaks down - inhibits the release of LH and FSH
50
how can hormones be used to reduce infertility
- oestrogen - taken everyday to be kept at high level prevent release of egg - inhibits FSH production - egg development & production stop & stay stopped - progesterone - stimulates thick mucus - prevents sperm getting through to reach egg - combined oral contraceptive - contains oestrogen & progesterone - 99% effective - side effects (headaches, nausea) - doesn’t protect from STDs - progesterone-only pill - fewer side effects - just as effective
51
what is the contraceptive patch
- contains oestrogen & progesterone - small 5cm x 5cm patch that’s stuck to the skin - each patch lasts a week
52
what is the contraceptive implant
- inserted under the skin of the arm - releases continuous amounts of progesterone - stops ovaries releasing eggs - makes it hard for sperm to swim to the egg - stops any fertilised eggs implanting in the uterus - implant can last for 3 years
53
what is the contraceptive injection
- contains progesterone - each dose lasts 2 - 3 months
54
what is an intrauterine device (IUD)
- t-shaped device that is inserted into the uterus to kill sperm & prevent implantation of a fertilised egg - two main types: • plastic IUDs - releases progesterone • copper IUDs - prevent the sperm surviving in the uterus
55
what is a diaphragm
shallow plastic cup that fits over the cervix to form a barrier - has to be used with spermicide
56
what is sterilisation
- cutting or tying the fallopian tubes in a female, or the sperm duct in a male - permanent procedure - small chance of the tubes rejoining
57
what hormones can be given to women in a fertility drug to stimulate ovulation
FSH and LH
58
pros & cons of fertility drug
pros: - helps a lot of women to get pregnant when they previously couldn’t cons: - doesn’t always work - some may have to do it many times - expensive - too many eggs could be stimulated - unexpected pregnancies (twins, triplets)
59
what is IVF
- in vitro fertilisation - involves collecting eggs from woman’s ovaries & fertilising them in a lab using the man’s sperm - can also involve ICSI - sperm is injected directly into the egg - useful if the man has low sperm count - fertilised egg are then grown into embryos in a laboratory incubator - once embryos are tiny balls of cells, one or two of them are transferred to the woman’s uterus to improve the chance of pregnancy - FSH & LH are given before egg collection to stimulate several eggs to mature
60
pros & cons of IVF
pro: - give an infertile couple a child cons: - multiple births can happen if more than one embryo grows into a baby - success rate of IVF is low - 26% in uk - some women have strong reactions to the hormones - abdominal pain, vomiting etc
61
why are some people against IVF
- process of IVF often results in unused embryos that are eventually destroyed - unethical - potential human life - genetic testing of embryos before implantation- unethical - could lead to selection of preferred characteristics
62
which gland releases adrenaline
the adrenal gland, just above the kidneys
63
when is adrenaline released
in response to stressful or scary situations - your brain detects fear or stress and senses nervous impulses to the adrenal glands, which respond by secreting adrenaline
64
what is thyroxine responsible for
- thyroxine is secreted by the thyroid gland - plays an important role in regulating basal metabolic rate - important for other processes such as stimulating protein synthesis for growth & development

biology paper 2 (3 decks)

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