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What are hormones (and the endocrine glands)
Hormones: chemicals released directly into blood. Carried in the blood to parts of the body, but only affect particular cells in target organs. Produced in various glands, called endocrine glands:
-Pituitary gland produces many hormones that regulate body conditions. Is the ‘master gland’.
-Thyroid gland produces thyroxine, which is involved in regulating things like the rate of metabolism, heart rate and temperature.
-Adrenal glands-Produce adrenaline for fight or flight response.
-Ovaries (female) produce oestrogen for menstrual cycle.
-Pancreas- produce insulin for regulating the blood glucose level.
-Testes (male) produce testosterone for controlling puberty and sperm production.
Difference between hormones and neurones
Neurones: -very fast -act for a very short time -act on a precise area
Hormones: -slower action -act for a long time -act in a more general way
How does adrenaline work?
Is the hormone released by the adrenal glands and prepares body for fight or flight by activating processes that increases the supply of oxygen and glucose to cells
How it works:
-adrenaline binds to specifics receptors in the heart, which causes the heart muscle to contract more frequently and with more force, so heart rate and blood pressure increases.
-This increases boood flow to the muscles so the cells receive more oxygen for increased respiration.-Adrenaline also binds to receptors in the liver. This causes live to break down it glycogen stores to release glucose.
-This increases the blood glucose level, so there’s more glucose in the blood to be transported to the cells.
Negative feedback
When your body detects that the levels of substance has gone above of below the normal level, it triggers a response to bring it back to the normal level.
What is thyroxine and what does it do?
Thyroxine is released by the thyroid gland. Regulates metabolic rate- the speed at which chemical reactions occur. A negative feedback system keeps the amount of thyroxine in the blood at the right level:
-when the blood thyroxine level is lower than normal, the hypothalamus is stimulated to release thyrotropin realising hormone (TRH).
-TRH stimulates the pituitary gland to release thyroid stimulating hormone (TSH).
-TSH stimulates the thyroid gland to release thyroxine, so blood thyroxine levels rises back to normal.
-When blood thyroxine level becomes higher than normal, the release of TRH from the hypothalamus is inhibited, which reduces the production of TSH, so blood thyroxine level falls.
Stages of the menstrual cycle.
1) menstruation starts (day 1). Lining of uterus breaks down and is released.
2) uterus lung is repaired (day 4 -14). This happens until it becomes a thick and spongy layer of blood vessels ready for a fertilised egg to implant.
3) egg develops and is released (day 14) from the ovary (ovulation).
4) the lining is maintained (for 14 days until day 28). If no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down again and the whole cycle starts over.
The menstrual cucle
FSH is released from pituitary gland.
Causes follicle to mature.
Maturing follicle produces oestrogen (causes uterus lining to thicken).
And, pituitary gland to produce LH.
Ovulation.
Follicle becomes corpus luteum.
Corpus luteum produces progesterone (which maintains uterus lining.
And, high levels of progesterone inhibits FSH release.
Corpus luteum and progesterone decreases.
FSH inhibitation is lifted.
Roles of the 4 hormones in the menstrual cycle.
1) FSH (follicle-stimulating hormone). Released by the pituitary gland. Causes a follicle (an egg and it’s surrounding cells) to mature in one of the ovaries. Stimulates production.
2) oestrogen. Released by the ovaries. Causes the lining of the uterus to thicken and grow. A high level stimulates an LH surge.
3) LH ( luteinising hormone). Released by pituitary gland. The LH stimulates ovulation at day 14- the follicle ruptured and the egg is released. Stimulates the remains of the follicle to develop into a structure called corpus luteum- which secretes progesterone.
4) progesterone. Released by the corpus luteum after ovulation. Maintains the lining of the uterus. Inhibits the release of FSH and LH. When the level of progesterone falls, and there’s a low oestrogen level, the uterus lining breaks down. A low progesterone level allows FdH to increase and be whole cycle starts again.
2 uses of hormones to treat infertility
Clomifene therapy.
Some women are infertiles as dont ovulate or not regularly. Can take drug called clomifene. Works by causing more FDH and LH to be released in body, which stimulate agh maturation and ovulation. By knowing when ovulating, couple can have intercourse during this period to increase chance of becoming pregnant.
IVF (in vitro fertilisation)
IVF involves collecting eggs from ovaries and fertilising in lad with sperm. These then grow into embryos, once tiny balls of cells, one or two of them are transferred to women’s uterus to improve chance of pregnancy. FSH and LH are given before egg collection to stimulate egg production. This is an example of Assisted Reproductive Technology (ART)- a fertility treatment that involves eggs being handled outside of body.
Types of contraceptives
Hormones can be used as contraceptives. Eg oestrogen can be used to prevent the release of a egg.
Progesterone can also be used to reduce fertility. Works in several ways, one of which is by stimulating the production of thick cervical mucus, which prevents sperm getting through the entrance to uterus and reaching egg.
Some contain both oestrogen and progesterone, which as the combing pull (oral contraceptive) and the contraceptive patch (worn in skin).
Mini pull and contraceptive injection both contain progesterone only.
Pregnancy can also be prevented by barrier methods.
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