Animal Hormones (Edexcel GCSE Combined Science: Biology): Flashcards

Compared with the nervous system, hormonal responses are slower to act but last for longer.

False.

Hormonal responses are slower to act than nervous responses, but their effects last for longer.

The 'fight or flight' hormone, produced by the adrenal glands when the body may be in danger, preparing it for movement.

It is produced in situations where the body may be in danger and prepares the body for movement (fight or flight).

It increases blood glucose concentration to allow increased respiration in muscle cells.

It increases both, so glucose and oxygen can be delivered to muscle cells, and carbon dioxide taken away, more quickly.

It diverts blood flow towards the muscles and away from non-essential parts such as the alimentary canal.

It dilates the pupils to allow as much light as possible to reach the retina, so more information can be sent to the brain.

Blood pressure increases.

The adrenal gland.

Adrenaline diverts blood flow towards the muscles and away from non-essential organs such as the alimentary canal.

Adrenaline increases heart rate and breathing rate so muscle cells receive more glucose and oxygen.

False.

Adrenaline diverts blood away from the alimentary canal and towards the muscles, ready for fight or flight.

A hormone released from the thyroid gland that stimulates the basal metabolic rate (BMR).

A mechanism in which a change away from the normal level triggers a response that brings the level back to normal.

In the neck; it releases thyroxine.

The speed at which chemical reactions occur in the body when it is at rest.

TSH (thyroid-stimulating hormone), released from the pituitary gland.

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.

TRH is released in the hypothalamus.

This increases the release of TSH from the pituitary gland.

TSH stimulates the thyroid to release more thyroxine.

A condition caused by an overactive thyroid gland secreting too much thyroxine, which increases BMR and protein synthesis.

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 thyroid gland and stimulates the basal metabolic rate.

True.

A rise in thyroxine inhibits TRH and TSH release, so less thyroxine is made; a fall does the opposite, returning levels to normal.

The release of a mature egg from the ovary, occurring around day 14 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.

Oestrogen and progesterone

FSH and LH (Higher Tier Only)

FSH causes maturation of an egg in the ovary; LH stimulates the release of the egg (ovulation).

Oestrogen is made by the ovaries; progesterone is made by the corpus luteum (the empty egg follicle).

FSH stimulates the development of a follicle in the ovary; an egg matures inside the follicle, which produces oestrogen.

It causes growth and repair of the uterus lining.

It inhibits the production of FSH (Higher Tier Only).

It causes ovulation around day 14.

It stimulates the release of LH from the pituitary gland (Higher Tier Only).

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 14, stimulating the release of LH, which causes ovulation.

A fall in progesterone levels causes the uterine lining to break down, a process known as menstruation.

True.

Oestrogen causes the lining to grow and repair; progesterone then maintains it, and menstruation follows when progesterone levels drop.

The use of methods to prevent pregnancy, helping to keep family sizes small and limit the increase in human population.

Avoiding sexual intercourse completely (a natural method).

It involves avoiding intercourse during the fertile period around ovulation; it is the least reliable method of birth control.

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.

They last several months and remove the risk of forgetting to take a pill, increasing effectiveness.

It releases hormones that thicken cervical mucus and thin the uterus lining, and it acts as a barrier to sperm passing through the uterus.

They prevent sperm from reaching the egg; condoms also protect against sexually transmitted infections (STIs).

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.

Barrier methods such as condoms.

Barrier methods such as the condom work by preventing sperm from reaching the egg.

The contraceptive pill raises levels of progesterone and oestrogen, which prevents the development of an egg.

False.

The pill only prevents pregnancy. Only barrier methods such as condoms also protect against STIs.

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.

When a couple find it difficult or are unable to conceive naturally.

A drug given to women to stimulate egg maturation and ovulation by causing more FSH and LH to be released.

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.

Assisted reproductive technology; IVF is an example because fertilisation initially occurs outside the body.

It can cause several eggs to be released at once.

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)

There is potential for it to be misused in choosing the characteristics of offspring (which is not allowed).

In IVF, the mother is given FSH and LH to stimulate the maturation of several eggs.

The drug clomifene stimulates egg maturation and ovulation by increasing the release of FSH and LH.

False.

In IVF the eggs are fertilised outside the body in the laboratory ('in vitro'); only the resulting embryos are placed into the uterus.