Biology - paper 2

What is homeostasis?
The regulation of the conditions inside your body 9and cells) to maintain a stable internal environment
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Why do the conditions inside your body need to be kept steady?
They need the right conditions in order to function properly and for enzyme action
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What are the three main components of the automatic control systems
receptors, coordination centres and effectors
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What is the role of the negative feedback?
When the level of something gets too high or too low your body uses negative feedback to bring it back to normal again
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What happens when a stimulus is too high?
Receptor detects a stimulus that is too high, CC receives and processes information and then organises a response.Effector produces a response which counteracts the change and restores optimum level ( decreases)
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What happens when a stimulus is too low?
Receptor detects a stimulus that is too low, CC receives and processes information then organises a response.Effector produces a response which counteracts the change and restores the optimum level (level increases)
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What is the role of the nervous system?
When humans can react to their surroundings and coordinate their behaviour
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What are the different parts of the nervous system?
Central nervous system, sensory neurones, motor neurones and effectors
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Where is the central nervous system located in animals?
In vertebrates (animals with backbones) this consists of the brain and spinal cord only
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Where is the central nervous system located in mammals?
Connected to the body by sensory and motor neurones
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What is the job of the sensory neurone?
The neurones carry information as electrical impulses from the receptors to the central nervous system
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What is the job of the motor neurone?
The neurones that carry electrical impluses from the central nervous system to the effectors
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What is the role of an effector?
Where all your muscles and glands respond to nervous impulses
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What is the role of a receptor? name some examples of a receptor
Receptors are the cells that detect stimuli.Taste on the tongue,sound in the ears
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What is the role of an effector? name some examples and their jobs
Responds to nervous impulses and bring about a change.Muscles and glands are effectors.Muscles contract in response to a nervous impulse and glands secrete hormones
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What is the connection between two neurones called?
a synapse
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How is the nerve signal moved?
The nerve signal is transferred by chemicals which diffuse across the gap
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What are reflexes?
Rapid,automatic responses to certain stimuli that dont evolve the conscious part of the brain.They can reduce the chances of being injured.
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What is the passage of information in a reflex called and what two things is it between?
Reflec arc from a receptor to an effector
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What are hormones?
chemical molecules released directly into the blood.They are only carried to the target organs
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Where are hormones produced/secreted by?
Hormones are produced in and secreted by various glands, called endocrine glands.These glands make up your endocrine system.
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What is the role of the pituitary gland?
Produces many hormones that regulate body conditions.it is sometimes called the master gland because these hormones act on each other glands directing them to release hormones that bring about change
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What is the role of the thyroid?
Produces thyroxine is involved in regulating things like the rate of metabolism, heart rate and temperature
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What is the role of the adrenal gland?
Produces adrenaline which is used to prepare the body for a 'fight or flight'
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What is the role of the pancreas?
Produces insulin which is used to regulate the blood glucose level
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What is the role of the ovaries?
produces oestrogen which is involved in the menstrual cycle
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What is the role of the testes?
produces testosterone which controls puberty and sperm production in males
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What are the differences between nerves and hormones?
Nerves have very fast action, act for a very short time and act on a precise area. Hormones have slower action, act for a long time and act in a more general way
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What happens at stage 1 of the menstruation cycle (day 1 )
menstruation starts.The uterus lining breaks down for about four days
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What happens at stage 2 (day 4 - 14)
The uterus lining builds up again into a thick spongy layer full of blood verses ready to receive a fertilised egg
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What happens at stage 3 (day 14)
An egg develop and is released from the ovary.This is called ovulation
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What happens at stage 4 (day 14-28)
The wall is then maintained for about 14 days.If no fertilised egg is landed on the uterus wall by day 28 the spongy lining starts to break down and the whole cycle starts again
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What four hormones is the menstrual cycle controlled by?
FSH (follicle-stimulating hormone),oestrogen,LH(luteinising hormone) and progesterone
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What is the role of the FSH (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
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What is the role of oestrogen?
Produced in the ovaries, causes the lining of the uterus to grow and stimulates the release of LH (which causes the realise of an egg) and inhibits realease of FSH
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What is the role of LH (luteinising hormone)
produced in the pituitary gland and stimulates the release of an egg at day 14
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What is the role of progesterone?
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 and inhibits the release of LH and FSH
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How can oestrogen prevent fertility?
it prevents the release of an egg so it stops egg development
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How can progesterone prevent fertility?
by stimulating the production of thick mucus which prevents any sperm getting through and reaching the egg
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What is the pill a combination of? how effective is it?
oestrogen and progesterone. over 99% effective
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Side effects of the pill and what does it not protect you against
headaches & nausea and doesn't protect you against STD's
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name some methods of contraception that use hormones
contraceptive patch,implant,injection and IUD
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contraceptive patch
patch that is stuck onto the skin and acts like a pill but lasts for 1 week
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contraceptive implant
inserted under the skin of the arm and releases continuous amounts of progesterone.it can last for 3 years
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contraceptive injection
contains progesterone and lasts for 2-3 months
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intrauterine device (IUD)
t shaped device inserted into the uterus to kill sperm and prevent implantation of a fertilised egg.Plastic IUD's release progesterone and copper IUD's prevent sperm surviving in the uterus
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Name some non hormonal forms of contraception
Condoms,diaphragm and spermicide
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condoms
worn over the penis during intercourse to prevent sperm entering the vagina.Can also be put inside the vagina. Only form of contraception that protect against STD' s
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diaphragm
shallow plastic cup that fits over the cervix to form a barrier. It has to be used with spermicide
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spermicide
can be used alone but is only 70-80% effective
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sterilisation
cutting or tying the fallopian tubes or sperm duct in a male.This is a permanent procedure however there is a very small chance that the tubes can rejoin
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natural methods
avoiding sexual intercourse when the female is most fertile
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abstinence
not having intercourse
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pros of using hormones for fertility
helps a lot of women to get pregs when they previously couldn't
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cons of using hormones for fertility
doesn't always work - some women may have to do it many times which is expensive.Too many eggs could be stimulated causing multiple pregnancies (twins/triplets)
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What does IVF involve?
collecting eggs from the woman ovaries and fertilising them in a lab using the mans sperm
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What is the technique 'intra-cytoplasmic sperm injection' ICSI
where the sperm is injecting directly into an egg.Its useful if the man has a very low sperm count
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Pros of fertility treatment
can give an infertile couple a child
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cons of fertility treatment
multiple births can happen if more than one embryo grows into a baby - higher risk of miscarriage and still birth.Success rate of IVF is lower (26%)(stressful and upsetting).Physically draining for the woman as some hormones cause abdominal pain,vomi
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Why are some people against IVF?
becauser the process of IVF often results in unused embryos being destroyed which is a potential human life.Genetic testing of embryos before implantation could raise ethical issues about selection of preferred characteristics
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Card 2

Front

Why do the conditions inside your body need to be kept steady?

Back

They need the right conditions in order to function properly and for enzyme action

Card 3

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What are the three main components of the automatic control systems

Back

Preview of the front of card 3

Card 4

Front

What is the role of the negative feedback?

Back

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Card 5

Front

What happens when a stimulus is too high?

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