Animal Hormones Flashcards
All 29 cards in this deck
How are hormones transported from an endocrine gland to their target organs?
In the blood (plasma), dissolved in solution.
Which hormone is produced by the testes?
Testosterone — it controls sperm production and male secondary sexual characteristics.
True or false? Hormonal responses are usually slower but longer-lasting than nervous responses.
True. Hormones travel in the blood to target organs, so they act more slowly but their effects last longer than nerve impulses.
Which endocrine gland releases adrenalin, and what response does it prepare the body for?
The adrenal glands; it prepares the body for fight or flight.
State three effects of adrenalin on the circulatory system in the fight-or-flight response.
Increased heart rate, increased blood pressure and increased blood flow to the muscles.
What effect does adrenalin have on liver cells?
It binds to receptors on the liver, triggering the cells to convert glycogen into glucose, which is released into the blood.
True or false? The extra glucose released during the fight-or-flight response is used in respiration to release energy for the working muscles.
True. More glucose and oxygen reach the muscles, so the rate of respiration increases and more energy (ATP) is released.
Which gland produces thyroxine, and what does thyroxine control?
The thyroid gland; thyroxine increases the metabolic rate.
What happens to TRH and TSH when thyroxine levels return to normal?
Thyroxine inhibits the release of TRH and the production of TSH, so less thyroxine is made.
What are the main stages of the menstrual cycle?
e.g. in a 28-day cycle
- Days 1–5: menstruation — the uterus lining breaks down and is lost.
- Days 5–14: oestrogen repairs and thickens the uterus lining.
- Day 14: ovulation — an egg is released; progesterone then maintains the lining.
Which hormone does the pituitary gland release at the start of the menstrual cycle, and what does it do?
FSH; it causes an egg to mature in a follicle in the ovary and stimulates the ovaries to release oestrogen.
Which hormone surges sharply just before ovulation, and what causes the surge?
LH, released from the pituitary gland; the surge is caused by high levels of oestrogen, and LH causes the egg to be released.
Which structure produces progesterone after ovulation, and what does the progesterone do?
The corpus luteum; progesterone maintains the lining of the uterus and inhibits FSH and LH.
Which two hormones are contained in the combined contraceptive pill?
Oestrogen and progesterone.
What effect do the high levels of oestrogen and progesterone in the combined pill have on FSH and LH?
They inhibit the production of FSH, so no eggs mature, and inhibit LH, so ovulation is prevented.
Apart from inhibiting FSH and LH, give one other way hormonal contraception prevents pregnancy.
It thickens the cervical mucus, blocking sperm from reaching the egg (it can also thin the uterus lining, reducing implantation).
True or false? The combined contraceptive pill protects against sexually transmitted infections (STIs).
False. It gives no protection against STIs; condoms (a barrier method) reduce the risk of STI transmission.
What does clomifene therapy do in a woman who does not ovulate regularly?
It causes the release of FSH and LH, so eggs develop and mature in the follicles and ovulation is stimulated.
Why can IVF help a woman whose Fallopian tubes are blocked?
Fertilisation happens outside the body and the fertilised egg is placed directly into the uterus.
Give two disadvantages of IVF treatment.
Success rates are low and it is expensive (it also carries a risk of multiple births).
What is a hormone?
A chemical messenger secreted by an endocrine gland directly into the blood, which carries it to target organs where it has its effect.
Why is the pituitary gland called the 'master gland'?
Its hormones act on other endocrine glands, stimulating them to release their own hormones (e.g. TSH acts on the thyroid, FSH on the ovaries).
What is metabolic rate?
How fast all the chemical reactions going on in the body's cells happen.
What does the hypothalamus release when the blood thyroxine level falls below normal?
TRH (thyrotropin-releasing hormone).
What does TSH do in the control of thyroxine levels?
TSH (thyroid-stimulating hormone) is released by the pituitary gland in response to TRH; it stimulates the thyroid gland to release thyroxine, so the level rises back to normal.
Why does the FSH level start to rise again at the end of a menstrual cycle in which no pregnancy occurs?
The progesterone level falls, so FSH is no longer inhibited and can increase, starting the next cycle.
How do barrier methods of contraception, such as condoms and diaphragms, prevent pregnancy?
They form a physical barrier that stops sperm from reaching the egg.
Give one advantage of hormonal contraception over barrier methods.
It is more effective at preventing pregnancy when used correctly, and the couple don't need to think about contraception each time they have sex.
Why are FSH and LH given to a woman before eggs are collected for IVF?
To stimulate several eggs to mature, so that more than one egg can be collected and fertilised.