Animal HormonesEdexcel GCSE Biology: Flashcards

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What is a hormone?

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What is a hormone?: A chemical messenger secreted by an endocrine gland into the blood, acting on a target organ.
Name the six endocrine glands.: Pituitary, thyroid, pancreas, adrenal glands, ovaries, testes.
Which gland produces adrenalin?: Adrenal glands.
Four effects of adrenalin?: Increased heart rate, blood pressure, blood flow to muscles, raised blood glucose.
Which gland produces thyroxine and its role?: Thyroid gland; controls metabolic rate.
Describe thyroxine's negative feedback loop.: Low thyroxine→TRH (hypothalamus)→TSH (pituitary)→thyroxine (thyroid)→normal levels inhibit TRH/TSH.
What triggers ovulation?: An LH surge.
Role of FSH?: Matures an egg and stimulates oestrogen production.
Role of oestrogen?: Repairs/thickens uterus lining, triggers LH surge, inhibits FSH at high levels.
Role of progesterone?: Maintains uterus lining, inhibits FSH/LH; falling levels trigger menstruation.
How does hormonal contraception prevent pregnancy?: Inhibits FSH so no eggs mature.
Advantage/disadvantage of barrier methods vs hormonal?: Advantage: protects against STIs. Disadvantage: less effective generally.
What is clomifene used for?: Stimulates FSH/LH to trigger ovulation in infertility treatment.
Outline IVF.: FSH/LH stimulate multiple eggs; fertilised outside body; embryo inserted into uterus.