Hormones in Humans: Reproduction & Metabolism (AQA GCSE Biology)
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What is the menstrual cycle?
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What is the menstrual cycle?
The menstrual cycle is the sequence of events that includes the thickening of the uterus lining, ovulation and menstruation; it is controlled by a series of hormones.
What is the role of oestrogen in the menstrual cycle?
Oestrogen is required to stimulate the thickening of the uterus lining.
What happens to oestrogen levels during the menstrual cycle? (Higher Tier Only)
Oestrogen levels rise from day 1 and peak just before day 14. The peak in oestrogen occurs just before the egg cell is released.
True or False?
An increase in progesterone results in the loss of the uterus lining.
False.
A decrease in progesterone levels at the end of the cycle results in the loss of the lining during menstruation.
What happens to progesterone levels during the menstrual cycle? (Higher Tier Only)
Progesterone levels are low from day 1 – 14 and starts to rise once ovulation has occurred. Levels then decrease towards the end of the cycle.
What is the role of FSH (follicle-stimulating hormone) in the menstrual cycle?
FSH is released by the pituitary gland and causes an egg to start maturing in the ovary.
What hormone is released by the pituitary gland to stimulate ovulation?
The pituitary gland is stimulated to release LH (luteinising hormone) which triggers ovulation (the release of an egg).
True or False?
LH causes egg cells to start to mature within the ovaries.
False.
LH causes ovulation to occur. It is FSH that causes an egg cell to begin to mature.
Define secondary sexual characteristics.
Secondary sexual characteristics are features that are not present at birth but that develop during puberty.
What are the two hormones that control the development of secondary sexual characteristics?
The two hormones that control the development of secondary sexual characteristics are:
Oestrogen (females)
Testosterone (males)
Give examples of secondary sexual characteristics that develop in females.
Examples of secondary sexual characteristics that develop in females include:
Breasts develop
Body hair grows
Widening of hips
Menstruation begins
Growth of sex organs
True or False?
Secondary sexual characteristics, such as growth of sex organs, voice breaking and growth of body hair, occur in males in response to the hormone oestrogen.
False.
The secondary sexual characteristics in males develop in response to the hormone testosterone. Oestrogen is involved with stimulating development of secondary sexual characteristics in females.
What causes the sudden peak in LH seen at day 14? (Higher Tier Only)
The peak in LH occurs as a result of oestrogen levels reaching a threshold, the release of LH then stimulates ovulation.
Describe the hormonal changes leading the menstrual cycle into stage 1?
Stage 1 occurs as a result of a drop in progesterone. This is because progesterone is responsible for maintaining the lining of the uterus, so when levels drop, the lining starts to break away.
Name two hormonal methods of contraception.
Hormonal methods of contraception include:
injection
implant
oral contraceptives e.g. pill
skin patch
hormonal coil/intrauterine device
What is an example of a barrier method of contraception?
Barrier methods include:
condoms
diaphragms
How does a spermicide prevent pregnancy?
Spermicide kills or disables the sperm so it is unable to fertilise the egg.
True or False.
Hormonal contraceptives that inhibit oestrogen, prevent the maturation of a follicle
False.
Oestrogen is not the hormone responsible for the maturation of the egg. Hormonal contraceptives that inhibit FSH production will ensure that no eggs mature.
Why might a women in her 20's be discouraged from sterilisation as contraception?
A woman who is 20 years old may be discouraged from sterilisation as she is young and may decide to have children at a later time.
True or False.
Some contraceptives are placed physically inside the uterus.
True.
The coil is an intrauterine device which either prevents implantation of an embryo or releases hormones to prevent fertilisation from occuring.
Why might it sometimes be recommended to use barrier methods of contraception over hormonal options?
Barrier methods of contraception might be recommended as they provide protection against sexually transmitted diseases.
Define the term infertility. (Higher Tier Only)
Infertility refers to the difficulty or inability of a couple to naturally conceive.
What hormones found in a fertility drug may stimulate the production of eggs in the ovaries? (Higher Tier Only)
A fertility drug may contain FSH to stimulate maturation of an egg, and LH to trigger ovulation.
True or False?
In Vitro Fertilisation (IVF) requires a surrogate to carry the developing embryo. (Higher Tier Only)
False.
IVF involves production of the embryo outside of the body, but the developing embryo is usually implanted back into the mothers uterus to develop to full term.
What are the main steps of IVF treatment? (Higher Tier Only)
The main stages of IVF are as follows:
IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs.
The eggs are collected from the mother and fertilised by sperm from the father in the laboratory.
The fertilised eggs develop into embryos.
At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb).
Suggest what negative factors might be associated with fertility treatments. (Higher Tier Only)
Negatives of fertility treatments might include:
Treatment is very emotionally and physically stressful.
The success rates are not high.
It can lead to multiple births which are a risk to both the babies and the mother.
True or False?
The use of IVF allows for eggs to be fertilised inside the body. (Higher Tier Only)
False.
The use of IVF allows for eggs to be fertilised outside the body.
What is an embryo? (Higher Tier Only)
Embryos are tiny balls of cells which develop from mitotic division of a fertilised egg.
What is the risk associated with implanting several embryos during IVF? (Higher Tier Only)
The risk associated with implanting several embryos is the high likelihood of multiple births, which increases the risk of miscarriage or stillbirths.
Why do some people oppose the production of more embryos than are used in IVF? (Higher Tier Only)
Some people oppose the practice of more embryos than are used because it raises ethical concerns about the ownership and potential destruction of unused embryos, which are considered potential life.
What is one potential benefit of fertility treatments? (Higher Tier Only)
One potential benefit of fertility treatments is that they provide couples with the chance to have a baby of their own.
True or False?
Blood glucose level and core body temperature control are examples of positive feedback. (Higher Tier Only)
False.
Blood glucose level and core body temperature control are examples of negative feedback.
Define 'negative feedback'. (Higher Tier Only)
Negative feedback refers to the mechanisms by which homeostasis maintains conditions within an optimal range.
A move away from the optimum results in mechanisms which return the conditions back towards the optimum.
True or False.
Thyroxine levels determine metabolic rate. (Higher Tier Only)
True.
Thyroxine from the thyroid gland stimulates the basal metabolic rate. It plays an important role in growth and development.
Where is adrenaline released from? (Higher Tier Only)
Adrenaline is released from the adrenal glands found just above the kidneys.
What is the function of adrenaline in the human body? (Higher Tier Only)
Adrenaline is a hormone produced by the adrenal glands in times of fear or stress, which increases heart rate and boosts the delivery of oxygen and glucose to the brain and muscles, preparing the body for 'flight or fight'.
True or False.
Adrenaline reduces heart rate. (Higher Tier Only)
False.
Adrenaline increases heart rate to increase blood flow to the muscles allowing for the fight or flight response.
How is the level of thyroxine controlled in the body? (Higher Tier Only)
The level of thyroxine is controlled by negative feedback where high levels of thyroxine leads to a series of events which results in a reduction thyroxine production. Low levels of thyroxine leads to a series of events which results in an increase in thyroxine production.
True or False?
Low levels of thyroxine result in low levels of protein synthesis. (Higher Tier Only)
True.
Protein synthesis is a metabolic reaction of the body. Low levels of thyroxine causes a decrease in metabolic activity and therefore a reduction in processes such as protein synthesis.
Define 'basal metabolic rate (BMR)'. (Higher Tier Only)
The basal metabolic rate (BMR) is the speed at which chemical reactions occur in the body when it is at rest.
How is the endocrine system responsible for the fight-or-flight response? (Higher Tier Only)
The endocrine system is the system of glands which are responsible for hormone release. This includes the release of the hormone adrenaline which prepares the body for fight or flight.