Animal Hormones (Edexcel GCSE Combined Science: Biology): Flashcards
Exam code: 1SC0
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- FrontThe Endocrine System
Hormone
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Cards in this collection (63)
Hormone
A chemical substance produced by a gland, carried in the blood to alter the activity of specific target cells, tissues or organs.
Endocrine gland
A group of cells that produces and releases hormones directly into the bloodstream.
How do the effects of the endocrine system compare with those of the nervous system?
Hormonal effects are slower to act but last for longer, so the endocrine system controls functions that do not need instant responses.
Which hormone does the pancreas produce and what does it do?
Insulin, which regulates blood glucose levels.
Which two hormones does the pituitary gland ('master gland') produce?
FSH and LH.
Which endocrine gland produces adrenaline?
The adrenal glands.
Which glands produce testosterone and oestrogen?
The testes produce testosterone; the ovaries produce oestrogen.
List five hormones of great importance in humans.
Adrenaline, insulin, testosterone, progesterone and oestrogen.
What is the role of progesterone?
It is produced in the ovaries and maintains the uterine lining during pregnancy.
Hormones are carried by the and alter the activity of specific cells, tissues or organs.
blood / target
Compared with the nervous system, hormonal responses are to act but last for .
slower / longer
Adrenaline (Higher Tier Only)
The 'fight or flight' hormone, produced by the adrenal glands when the body may be in danger, preparing it for movement.
Why is adrenaline known as the 'fight or flight' hormone? (Higher Tier Only)
It is produced in situations where the body may be in danger and prepares the body for movement (fight or flight).
How does adrenaline affect blood glucose concentration, and why? (Higher Tier Only)
It increases blood glucose concentration to allow increased respiration in muscle cells.
What effect does adrenaline have on heart rate and breathing rate, and why? (Higher Tier Only)
It increases both, so glucose and oxygen can be delivered to muscle cells, and carbon dioxide taken away, more quickly.
How does adrenaline change blood flow around the body? (Higher Tier Only)
It diverts blood flow towards the muscles and away from non-essential parts such as the alimentary canal.
What effect does adrenaline have on the pupils, and why? (Higher Tier Only)
It dilates the pupils to allow as much light as possible to reach the retina, so more information can be sent to the brain.
What happens to blood pressure when adrenaline is released? (Higher Tier Only)
Blood pressure increases.
Which gland releases adrenaline? (Higher Tier Only)
The adrenal gland.
Adrenaline diverts blood flow towards the and away from non-essential organs such as the canal. (Higher Tier Only)
muscles / alimentary
Adrenaline heart rate and breathing rate so muscle cells receive more glucose and . (Higher Tier Only)
increases / oxygen
Thyroxine (Higher Tier Only)
A hormone released from the thyroid gland that stimulates the basal metabolic rate (BMR).
Negative feedback (Higher Tier Only)
A mechanism in which a change away from the normal level triggers a response that brings the level back to normal.
Where is the thyroid gland located and what does it release? (Higher Tier Only)
In the neck; it releases thyroxine.
What is the basal metabolic rate (BMR)? (Higher Tier Only)
The speed at which chemical reactions occur in the body when it is at rest.
Which hormone controls thyroxine levels, and where is it released from? (Higher Tier Only)
TSH (thyroid-stimulating hormone), released from the pituitary gland.
What happens when thyroxine levels are normal or too high? (Higher Tier Only)
TRH production is inhibited in the hypothalamus.
The release of TSH from the pituitary gland is therefore inhibited.
Less thyroxine is released from the thyroid gland.
What happens when thyroxine levels fall below normal? (Higher Tier Only)
TRH is released in the hypothalamus.
This increases the release of TSH from the pituitary gland.
TSH stimulates the thyroid to release more thyroxine.
What is hyperthyroidism? (Higher Tier Only)
A condition caused by an overactive thyroid gland secreting too much thyroxine, which increases BMR and protein synthesis.
What is hypothyroidism? (Higher Tier Only)
A condition caused by an underactive thyroid gland secreting too little thyroxine, which can lead to heart and nerve problems, and death.
Thyroxine is released from the gland and stimulates the basal rate. (Higher Tier Only)
thyroid / metabolic
Ovulation
The release of a mature egg from the ovary, occurring around day 14 of the menstrual cycle.
What are the four stages of the menstrual cycle?
Menstruation – loss of the uterus lining at the start of the cycle.
The lining starts to thicken.
Ovulation occurs around day 14.
The lining is maintained ready to accept a fertilised egg.
Name the hormones that control the menstrual cycle?
Oestrogen and progesterone
FSH and LH (Higher Tier Only)
What are the roles of FSH and LH in the menstrual cycle? (Higher Tier Only)
FSH causes maturation of an egg in the ovary; LH stimulates the release of the egg (ovulation).
Where are oestrogen and progesterone produced?
Oestrogen is made by the ovaries; progesterone is made by the corpus luteum (the empty egg follicle).
How does FSH lead to oestrogen production? (Higher Tier Only)
FSH stimulates the development of a follicle in the ovary; an egg matures inside the follicle, which produces oestrogen.
What two effects does oestrogen have as its level rises?
It causes growth and repair of the uterus lining.
It inhibits the production of FSH (Higher Tier Only).
What happens when oestrogen reaches a high enough level? (Higher Tier Only)
It causes ovulation around day 14.
It stimulates the release of LH from the pituitary gland (Higher Tier Only).
What is the role of progesterone, and what happens if the egg is not fertilised?
Progesterone maintains the uterus lining.
If the egg is not fertilised, the corpus luteum breaks down and progesterone levels drop, causing menstruation.
Oestrogen levels rise to peak just before day , stimulating the release of , which causes ovulation. (Higher Tier Only)
14 / LH
A fall in levels causes the uterine lining to break down, a process known as .
progesterone / menstruation
Contraception
The use of methods to prevent pregnancy, helping to keep family sizes small and limit the increase in human population.
What is abstinence as a method of contraception?
Avoiding sexual intercourse completely (a natural method).
How does the rhythm method work, and how reliable is it?
It involves avoiding intercourse during the fertile period around ovulation; it is the least reliable method of birth control.
How does the contraceptive pill prevent pregnancy?
It contains progesterone (or progesterone and oestrogen), which maintain the uterus lining and prevent the development of another egg, so no egg is released to be fertilised.
What is one advantage of a contraceptive implant or injection over the pill?
They last several months and remove the risk of forgetting to take a pill, increasing effectiveness.
How does an IUD/IUS prevent pregnancy?
It releases hormones that thicken cervical mucus and thin the uterus lining, and it acts as a barrier to sperm passing through the uterus.
How do barrier methods such as condoms work, and what extra protection do condoms give?
They prevent sperm from reaching the egg; condoms also protect against sexually transmitted infections (STIs).
What is the difference between a vasectomy and female sterilisation?
In a vasectomy the sperm ducts are cut so no sperm is in the semen; in female sterilisation the oviducts are cut or tied so eggs cannot reach the uterus. Both are very effective but difficult to reverse.
Which contraceptive methods also protect against sexually transmitted infections?
Barrier methods such as condoms.
Barrier methods such as the work by preventing from reaching the egg.
condom / sperm
The contraceptive pill raises levels of and oestrogen, which prevents the development of an .
progesterone / egg
IVF (in vitro fertilisation) (Higher Tier Only)
A fertility treatment in which eggs are fertilised by sperm outside the body, before one or two embryos are placed in the mother's uterus.
What is infertility? (Higher Tier Only)
When a couple find it difficult or are unable to conceive naturally.
What is clomifene and how does it work? (Higher Tier Only)
A drug given to women to stimulate egg maturation and ovulation by causing more FSH and LH to be released.
Outline the main steps of IVF treatment. (Higher Tier Only)
The mother is given FSH and LH to stimulate the maturation of several eggs.
The eggs are collected and fertilised by sperm in the laboratory.
The fertilised eggs develop into embryos.
One or two tiny embryos are inserted into the mother's uterus.
What does ART stand for, and why is IVF an example of it? (Higher Tier Only)
Assisted reproductive technology; IVF is an example because fertilisation initially occurs outside the body.
Why does clomifene therapy increase the chance of multiple births? (Higher Tier Only)
It can cause several eggs to be released at once.
Give two issues to consider with IVF treatment. (Higher Tier Only)
The success rate is low (~30%) and failures can be emotionally and physically stressful; and there is a high risk of multiple births, which increases the risk of miscarriage or stillbirth. (Any two)
Why is the use of genetic testing on embryos controversial? (Higher Tier Only)
There is potential for it to be misused in choosing the characteristics of offspring (which is not allowed).
In IVF, the mother is given and LH to stimulate the maturation of several . (Higher Tier Only)
FSH / eggs
The drug stimulates egg maturation and by increasing the release of FSH and LH. (Higher Tier Only)
clomifene / ovulation
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