Hormones

• Hormones


  Chemical messengers secreted by glands and carried in the blood to target cells
• Major endocrine glands


  • Thyroid
  • Adrenal glands
  • Testes (males)
  • Pituitary gland
  • Pancreas
  • Ovaries (females)
• Testosterone


  The male sex hormone produced by the testes that causes male secondary sexual characteristics to develop
• Oestrogen and progesterone


  The female sex hormones produced by the ovaries that cause female secondary sexual characteristics to develop and are involved in fertility and the menstrual cycle
• Pituitary gland


  A pea-sized gland at the base of the brain that releases many hormones and controls several other glands
• Thyroxine


  A hormone secreted by the thyroid gland that regulates growth and rates of chemical reactions
• Adrenaline


  A hormone secreted by the adrenal glands in times of stress that prepares the body for action
• The temperature of the extremities is cooler than the core body temperature, as they have a larger surface area and do not contain the major organs
• Puberty


  A process that occurs during adolescence it changes a child's body into an adult body - capable of sexual reproduction
• Important hormones in puberty

  • Oestrogen
  • Testosterone
• Oestrogen


  Causes thickening of the lining of the vagina and uterus, widening of the hips, and growth of breasts
• Testosterone


  Causes growth of tissues in the testicles can make sperm and growth of the penis
• Hormones involved in menstrual cycle

  • Follicle Stimulating Hormone (FSH)
  • Luteinising Hormone (LH)
  • Oestrogen
  • Progesterone
• Hormone Control - Negative Feedback

  1. FSH stimulates egg to mature

  2. LH releases mature egg

  3. Oestrogen thickens uterus lining

  4. Progesterone maintains uterus lining
• How a contraceptive pill containing progesterone works


  Progesterone stops the secretion of LH, without LH, ovulation does not happen, no ovum is released
• Follicle Stimulating Hormone (FSH) is released in the pituitary gland and is targeted towards the ovaries
• Oestrogen is released in the ovaries and targeted to the uterus (and pituitary gland)
• Luteinising hormone (LH) is released in the pituitary gland and is targeted towards the ovaries
• Progesterone is released by follicle cells in the ovaries and is targeted towards the uterus (and pituitary gland)
• During the first part of the menstrual cycle, an egg matures inside one of the ovaries.
• The matured egg is then released from its follicle into the fallopian tube where it can be fertilised by sperm if sexual intercourse has taken place around this time.
• If no fertilisation occurs, the corpus luteum breaks down and stops producing progesterone which causes the endometrium to break away and leave the body as blood during menstruation.
• The menstrual cycle lasts 28 days and is divided into 4 phases: Ovulation, Luteal phase, Follicular phase, and Menstrual phase
• As FSH increases, so does the production of oestrogen.
• Contraceptive pills do not prevent the spread of STIs
• Condoms are a physical barrier and therefore can reduce the risk of pregnancy and the spread of STIs