Animal Hormones Flashcards
All 37 cards in this deck
What is a hormone?
A chemical messenger produced by an endocrine gland and carried in the blood to its target organ.
How do hormones get from an endocrine gland to their target organ?
The gland secretes them directly into the bloodstream, and the blood carries them around the body to target organs that have receptors for them.
Which hormones are released by the pituitary gland?
FSH, LH, TSH (and ADH).
Which hormone is released by the thyroid gland?
Thyroxine.
Which hormones are released by the ovaries and by the testes?
Ovaries: oestrogen and progesterone. Testes: testosterone.
True or false? Hormones are carried to their target organs along nerves.
False. Hormones are carried in the blood; only electrical impulses travel along nerves.
Which gland releases adrenalin, and in what situation?
The adrenal glands, when a person is frightened or stressed, to prepare the body for fight or flight.
What effect does adrenalin have on heart rate, blood pressure and blood flow to the muscles?
It increases all three: heart rate up, blood pressure up, and more blood flowing to the muscles.
How does adrenalin raise blood sugar levels?
It stimulates the liver to convert glycogen into glucose, which is released into the blood.
Why does the release of adrenalin improve an athlete's performance?
More glucose and oxygen reach the muscles, increasing the rate of respiration to release more energy for the working muscles.
True or false? Adrenalin makes the liver convert glucose into glycogen.
False. Adrenalin makes the liver convert glycogen into glucose, raising blood sugar levels.
What is meant by the 'fight or flight' response?
The body being prepared by adrenalin to either fight a danger or run away from it.
What does thyroxine control in the body?
Metabolic rate (it also affects protein synthesis, growth and development).
What is metabolic rate?
The rate at which the chemical reactions in the body's cells take place, so the rate at which energy is used.
What is negative feedback?
A control mechanism in which a change away from the normal level triggers a response that brings the level back to normal.
What are the steps of negative feedback control of thyroxine?
e.g. blood thyroxine level falls below normal
- Hypothalamus produces TRH.
- TRH makes the pituitary gland release TSH.
- TSH acts on the thyroid, which releases more thyroxine, returning the level to normal.
What happens when thyroxine levels in the blood are normal or high?
Thyroxine inhibits the release of TRH from the hypothalamus and the production of TSH by the pituitary, so less thyroxine is made.
True or false? If a damaged thyroid gland stops making thyroxine, the level of TSH in the blood will fall.
False. TSH rises, because there is no thyroxine to inhibit TRH and TSH production.
What is the role of FSH in the menstrual cycle?
Released by the pituitary; it makes an egg mature in a follicle in the ovary and stimulates the ovaries to produce oestrogen.
What does a surge of LH cause in the menstrual cycle?
Ovulation — the release of the mature egg from the ovary, around day 14.
What is the role of oestrogen in the menstrual cycle?
It makes the lining of the uterus repair and thicken; at high levels it inhibits FSH and stimulates the release of LH.
Which structure produces progesterone, and what does it do?
The corpus luteum in the ovary; progesterone maintains the thickened uterus lining and inhibits FSH and LH.
What causes menstruation at the end of the menstrual cycle?
Progesterone and oestrogen levels fall, so the uterus lining breaks down and is lost (days 1–5).
What effect do the low oestrogen levels of women over about 50 have on ovulation?
Oestrogen levels are too low for LH to be released, and a surge of LH is needed for ovulation, so ovulation is unlikely.
Which hormones does the combined contraceptive pill contain?
Oestrogen and progesterone.
How does a high level of oestrogen in hormonal contraception prevent pregnancy?
It inhibits the production of FSH, so no eggs mature in the follicles and there is no egg to be fertilised.
How does progesterone in hormonal contraception prevent pregnancy?
It inhibits the production of LH so ovulation does not happen, and it thickens the cervical mucus so sperm cannot reach an egg.
Name two barrier methods of contraception and state how they work.
Condom (male or female) and diaphragm; they stop sperm reaching the egg.
Give two disadvantages of hormonal contraception such as the pill.
It must be taken regularly or it is less effective, and it can cause side effects; it also gives no protection against STIs.
True or false? The rhythm (calendar) method is a barrier method of contraception.
False. It uses no barrier — intercourse is avoided around the fertile time of the cycle.
What does IVF stand for?
In vitro fertilisation.
What are the main steps of IVF treatment?
e.g. a woman with blocked Fallopian tubes
- FSH and LH are given so several eggs mature.
- Eggs are collected and fertilised with sperm outside the body.
- Fertilised eggs develop into embryos and one or two are implanted into the uterus.
What is clomifene therapy used to treat?
Infertility in a woman who does not ovulate regularly, or does not ovulate at all.
How does clomifene therapy increase the chance of pregnancy?
It causes more FSH and LH to be released, so eggs develop and mature in the follicles and ovulation occurs.
True or false? IVF can help a woman with blocked Fallopian tubes to become pregnant.
True. Fertilisation happens outside the body, so the fertilised egg can be implanted directly into the uterus.
Give one disadvantage of fertility treatment using hormones and IVF.
There is an increased risk of multiple births (twins or triplets); success rates are also low.
True or false? Menstruation is the release of an egg cell from the ovary.
False. Menstruation is the breakdown and loss of the uterus lining; the release of an egg cell is ovulation, around day 14.