B3.2 - The Endocrine System Flashcards
What are hormones?
Chemical messengers made by endocrine glands
Transported via the bloodstream to target organs to cause a response in specific cells
What is thyroxine?
A hormone produced by the thyroid gland
Plays a vital role in regulating the body’s metabolic rate
What is the function of the thyroid gland?
To convert iodine into thyroxine by combining it with tyrosine (an amino acid)
How are thyroxine levels controlled?
The body needs more energy - hypothalamus causes pituitary gland to release TSH (thyroid-stimulating hormone)
TSH stimulates thyroid gland to release thyroxine - increase metabolic rate so cells transfer more energy
Cells have enough energy - hypothalamus inhibits TSH production
Thyroid gland stops releasing thyroxine
What is the function of FSH (follicle-stimulating hormone) ?
Secreted by pituitary gland
Travels to ovaries and causes egg to mature
Stimulates ovaries to produce oestrogen
What is the function of oestrogen?
Made in ovaries
Causes build up of uterus lining
What is the function of LH (luteinising hormone) ?
When levels reach a peak in the middle of the cycle, ovulation is triggered
What is the function of progesterone?
Maintains uterus lining
What are some non-hormonal contraceptive techniques?
Condom
Cervical cap
Intrauterine device
What do condoms do?
Non-hormonal
Short term contraceptive
Prevents sperm entering vagina
Prevents spread of STIs
What do cervical caps do?
Non-hormonal
Removed after 6 hours
Covers cervix to prevent sperm cells from entering vagina
What is an IUD?
Non-hormonal
Remains effective for 5-10 years
Releases copper to prevent sperm surviving in the uterus and fallopian tubes
What are some hormonal contraceptives?
Oestrogen and progesterone pills
Progesterone pills
Intrauterine system
What are oestrogen and progesterone pills?
Hormonal
Taken daily for 21 days of menstrual cycle
Prevents ovulation by thickening mucus in cervix
Stops sperm from reaching ovum and the ovum implanting in the uterus wall
What is a progesterone pill?
Hormonal
Taken daily around the same time
Thickens mucus in cervix
Stops sperm reaching ovum
Thickens uterus lining preventing implantation
Prevents ovulation
What is an IUS?
Hormonal
Remains effective for 3-5 years
Thickens mucus in cervix
Stops sperm reaching ovum
Thickens uterus lining preventing implantation
Prevents ovulation
What are some causes of infertility?
Blocked sperm ducts
Low sperm production
Lack of mature eggs being produced
Failure of ovaries releasing an egg
How does IVF work?
Doctors collect eggs from the mother and sperm from the father and fertilise them outside the body.
Could result in no or multiple pregnancies
What is a tropism?
A plant’s response to a stimulus
What is phototropism?
A plant’s response to light
What is geotropism?
A plant’s response to gravity
What is negative tropism?
A plant‘s response away from a stimulus
What is positive tropism?
A plant‘s response towards a stimulus
What is hydrotropism?
A plant‘s response to water
What is auxin and its function?
A plant hormone responsible for controlling the direction of plant growth at the meristems of the roots and stem in response to light, water and gravity
How does auxin work?
Made at the meristems
Moved to older parts of the stem and root to make the cells more elastic
More elastic cells absorb more water and grow longer, causing it to bend
What do gibberellins do?
Promotes stem elongation
Ends dormancy period in seeds and buds, letting shoots and flowers open
What does ethene do?
Causes fruit to ripen by stimulating starch to sugar conversion
What are some commercial uses of auxin?
Weed killers
Rooting powder
What are some commercial uses of gibberellins?
Used on fruits such as grapes to grow more
What are some commercial uses of ethene?
Plant ripening
