biology p2 t7

• the endocrine system sends hormones (chemical messengers) around the body. The blood carries the hormone to a target organ where it produces and effect.
• target organ: an organ affected by a specific hormone.
• The pituitary gland is also known as the master gland.
• The pancreas controls blood glucose levels.
• The thyroid gland controls metabolic rate, heart rate and temperature.
• The testes secrete testosterone and are involved in the production of sperm.
• adrenaline: this is a hormone that is secreted by the adrenal glands to prepare the body for a flight or flight response. In frightening situations, there is an increase in impulses from neurones reaching the adrenal glands.
• effects of adrenaline: and increased heart rate and blood pressure, and increase in blood flow to the muscles, and increase in blood sugar levels.
• metabolic rate: the rate at which biochemical reactions occur within cells.
• The conditions needed to measure resting metabolic rate are: a warm room, to be long after a mean, and for the body to be at rest. This is to prevent energy loss.
• metabolic rate: low levels of thyroxine stimulate the production of TRH from the hypothalamus. This then stimulates the release of TSH from the pituitary gland. This then causes the release of thyroxine from the thyroid gland.
• ART is using hormones to achieve pregnancy. Some examples are IVF and clomifene
• Clomifene therapy: This is a drug given to women who are not ovulating. The drug blocks the action of oestrogen. This causes a surge in LH and can promote ovulation.
• IVF: The mother is give FSH and LH to encourage the release and maturation of eggs. These are extracted from the mother and fertilised in the lab using sperm. These fertilised eggs then develop into embryos and are inserted into the uterus.
• IVF:

  Benefits:

  • provides a way for an infertile couple to have a child.

  Cons:

  • it can be physically stressful for women as they could have a reaction to the hormones.
  • It is very expensive.
  • There is a low success rate.
• menstrual cycle:

  • day 1-4 (menstruation) - the uterus lining breaks down and is lost with the unfertilised egg cell.
  • day 4-14 (egg development) - the egg starts to mature in the ovaries and the lining of the uterus begins to build back up.
  • day 14 (ovulation) - an egg cell is released from an ovary.
  • day 14-28 (uterus lining) - the uterus lining continues to thicken and the cycle starts again.
• menstrual hormones:

  FSH stimulates egg development within the follicle. It is produced in the pituitary gland and stimulates the ovaries to secrete oestrogen.
• menstrual hormones:

  Oestrogen causes the uterus lining to grow again. It is secreted from the ovaries. It inhibits FSH and stimulates the production of LH.
• menstrual hormones:

  LH stimulates ovulation and the development of the corpus luteum. It is produced in the pituitary gland.
• menstrual hormones:

  Progesterone maintains the lining of the uterus. It is produced in the ovaries and is secreted by the corpus luteum. It inhibits FSH and LH.
• The order of the menstrual hormones is FSH, oestrogen, LH and progesterone.
• contraception: a method or device used to prevent pregnancy.
• Some hormonal methods or contraception are the pill, implant, injection, patch and IUD.
• Some non-hormonal methods of contraception are spermicides, barrier methods, abstaining and surgery.
• the combined pill: this contains both progesterone and oestrogen. This causes oestrogen to remain high, inhibiting FSH so no eggs mature. It also causes cervical mucus to thicken so sperm cannot enter the uterus. Possible side effects are changes in mood, depression and high blood pressure.
• progesterone pill: causes a layer of cervical mucus to develop to prevent sperm getting through.
• contraceptive patch: this contains oestrogen and progesterone. It lasts for 1 week.
• contraceptive implant: releases continuous amounts of progesterone. It prevents the ovaries from releasing any eggs, it thickens cervical mucus, and it stops fertilised eggs from embedding in the uterus. It can last for 3 years.
• IUD: this releases progesterone and has the same effect as the implant. It lasts for 5-10 years.
• contraceptive injection: this is made up of progesterone and has the same effect as the implant. It lasts 2-3 months.
• spermicides: these kill or disable sperm. They are 70%-80% effective. A disadvantage is that it can cause allergic reactions.
• barrier methods: these include condoms and diaphragms. They prevent sperm from reaching the egg and can protect from STIs.
• abstaining: this is not having sex which ensures an egg is not fertilised.
• surgical methods: This is also known as sterilisation. For males it can be a vasectomy. For females it can be the cutting or tying of fallopian tubes.
• homeostasis: the maintenance of a stable internal environment in the body, despite fluctuations in internal and external conditions.
• Homeostasis is important to maintain enzyme action and cell functions including growth, replication and controlled cell death. In the human body, homeostasis controls blood glucose concentration, body temperature and water levels.
• receptors: cells that detect stimuli
• co-ordination centres: process information received from receptors.
• effectors: bring about a response to bring conditions in the body back to optimum levels.
• blood glucose: when blood glucose levels fall, the pancreas produces glucagon. The liver then turns glycogen into glucose, which is released into the blood.