Hormones - Aqa Gcse Science A Specification

žHormones are used in some forms of contraception and fertility treatments. Plants also produce hormones and respond to external stimuli.

žEvaluate the benefits of, and the problems that arise from, the use of hormones to control fertility, including IVF. žBenefits ¡Overcome infertility ¡Pre-implantation genetic diagnosis ¡Embryo selection ¡Cryopreservation žProblems ¡Costly ¡Profit-driven ¡Religious response ¡Unwanted embryos ¡Birth defects http://en.wikipedia.org/wiki/In_vitro_fertilisation#Ethics

žAny growth response that results in plant organs žcurving toward or away from stimuli is called a žtropism. žThe growth of a shoot in response to light is called phototropism. ¡Moving toward sunlight helps a growing plant use sunlight to drive photosynthesis. ¡Phototropism can result when the cells on the dark side of a plant stem elongate faster than those on the light side.

žStudies of plant responses to light led to the first evidence of plant hormones, a chemical signal ¡ produced in one part of the body and ¡transported to other parts, ¡where it acts on target cells to change their functioning. žCharles Darwin and his son Francis conducted experiments that showed that the shoot tips of plants controlled their ability to grow toward light.

žWhen plant tips were removed, plants did not grow toward light. žWhen plant tips were covered with an opaque cap, they did not grow toward light. žWhen plant tips were covered with a clear tip, they did grow toward light.

žEvaluate the use of plant hormones in horticulture as weedkillers and to encourage the rooting of plant cuttings. žAgricultural uses of plant hormones include ¡control of fruit production, ripening, and dropping, ¡production of seedless fruits, and ¡use as weed killers. žAgricultural uses of plant hormones ¡help keep food prices down and ¡can benefit the environment in aspects such as soil erosion, but ¡may have dangerous side effects for humans and the environment.

žMany processes within the body are coordinated by chemical substances called hormones. Hormones are secreted by glands and are usually transported to their target organs by the bloodstream. žHormones regulate the functions of many organs and cells. For example the monthly release of an egg from a woman's ovaries and the changes in the thickness of the lining of her womb are controlled by hormones secreted by the pituitary gland and by the ovaries.

žIn mammals žHormones have the following effects on the body: žstimulation or inhibition of growth žwake-sleep cycle and other circadian rhythms žmood swings žinduction or suppression of apoptosis (programmed cell death) žactivation or inhibition of the immune system žregulation of metabolism žpreparation of the body for mating, fighting, fleeing, and other activity žpreparation of the body for a new phase of life, such as puberty, parenting, and menopause žcontrol of the reproductive cycle žhunger cravings žsexual arousal žA hormone may also regulate the production and release of other hormones. Hormone signals control the internal environment of the body through homeostasis. http://en.wikipedia.org/wiki/List_of_human_hormones

žSeveral hormones are involved in the menstrual cycle of a woman. Hormones are involved in promoting the release of an egg: ¡ Follicle stimulating hormone (FSH) is secreted by the pituitary gland and causes eggs to mature in the ovaries. It also stimulates the ovaries to produce hormones including oestrogen. ¡Luteinising hormone (LH) stimulates the release of eggs from the ovary. ¡Oestrogen is secreted by the ovaries and inhibits further production of FSH.

žThe use of hormones in controlling fertility includes: ¡Giving oral contraceptives that contain hormones to inhibit FSH production so that no eggs mature ¢Oral contraceptives may contain oestrogen and progesterone to inhibit egg maturation ¢The first birth control pills contained large amounts of oestrogen. These resulted in women suffering significant side effects ¢Birth control pills now contain a much lower dose of oestrogen, or progesterone only ¢Progesterone only pills lead to fewer side effects.

žThe use of hormones in controlling fertility includes: ¡Giving FSH and LH in a 'fertility drug' to a woman whose own level of FSH is too low to stimulate eggs to mature, for example in IVF. ¢IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs. The eggs are collected from the mother and fertilised by sperm from the father. The fertilised eggs develop into embryos. At the stage where they are a tiny ball of cells, one or two embryos are inserted into the mother's uterus.

Hormones regulate the functions of many organs. Complete the following sentences. 1 (a) Hormones control the monthly release of an egg from the woman's .............................. . (1 mark) 1 (b) Hormones also control the thickness of the lining of her .................................. . (1 mark) 1 (c) Hormones given to women to stimulate the release of eggs are called .................................drugs. (1 mark) a - ovary, b - uterus, c - fertility 3 marks

Read the information about the trialling of the first contraceptive pill. The Pill was developed by a team of scientists led by Gregory Pincus. The team needed to carry out large scale trials on humans. In the summer of 1955, Pincus visited the island of Puerto Rico. Puerto Rico is one of the most densely populated areas in the world. Officials supported birth control as a form of population control. The women in Puerto Rico were mainly poor and uneducated. The scientists selected a pill with a high dose of hormones. The Pill was found to be 100 % effective when taken properly. But 17 % of the women in the study complained of side effects. The women in the trial had been told only that they were taking a drug that prevented pregnancy. They had not been told that the Pill was experimental or that there was a chance of dangerous side effects. Evaluate the issues involved with methods used by Pincus in trialling the contraceptive pill. (6 marks)