Topic 7 ~ Animal Coordination, Control and Homeostasis

• Hormones


  Chemical messengers sent around the body by the endocrine system
• Glands that secrete hormones

  • Pituitary gland
  • Pancreas
  • Thyroid
  • Adrenal gland
  • Ovary
  • Testes
• Pituitary gland


  The master gland that secretes hormones into the blood to either have an effect on the body or act on other glands to stimulate them to produce different hormones
• Pancreas


  Secretes insulin to control blood glucose levels
• Thyroid


  Secretes thyroxine to control metabolic rate, heart rate and temperature
• Adrenal gland


  Secretes adrenaline and is involved in the 'fight or flight' response
• Ovary


  Secretes oestrogen and is involved in the menstrual cycle and the development of female secondary sexual characteristics
• Testes


  Secretes testosterone and is involved in the production of sperm and the development of male secondary sexual characteristics
• The blood transports hormones to target organs or tissues where they have an effect
• Compared to the nervous system, the hormonal system is much slower but it acts for longer
• Adrenaline


  A hormone produced by the adrenal glands to prepare the body for a 'fight or flight' response
• Fight or flight response

  1. Increased heart rate

  2. Increased blood pressure

  3. Increased blood flow to muscles

  4. Increased blood sugar levels
• Thyroxine


  Regulates metabolic rate and is important in growth and development
• Regulation of thyroxine levels

  1. Low thyroxine stimulates TRH production in hypothalamus

  2. TRH causes release of TSH from pituitary

  3. TSH acts on thyroid to produce thyroxine

  4. High thyroxine inhibits release of TRH to stop production of TSH
• Negative feedback


  The mechanism by which thyroxine levels are controlled
• Hormones involved in the menstrual cycle

  • Follicle stimulating hormone (FSH)
  • Oestrogen
  • Luteinising hormone (LH)
  • Progesterone
• Follicle stimulating hormone (FSH)


  Causes maturation of egg in ovary
• Oestrogen


  Causes lining of uterus to grow
• Luteinising hormone (LH)


  Its release results in ovulation
• Progesterone


  Maintains lining of uterus and supports pregnancy if egg is fertilised
• Hormonal contraception methods


  • Combined pill (oestrogen and progesterone)
  • Progesterone only pill
  • Contraceptive patch
  • Contraceptive implant
  • Contraceptive injection
  • Intrauterine device (IUD)
• Combined pill


  Constantly high oestrogen levels inhibit FSH so no eggs mature, and thickens cervical mucus to prevent sperm movement
• Progesterone only pill


  Has less side effects than combined pill
• Contraceptive patch


  Contains oestrogen and progesterone, lasts for 1 week
• Contraceptive implant


  Releases continuous progesterone to prevent ovulation, thicken cervical mucus and stop fertilised eggs implanting
• Contraceptive injection


  Made of progesterone, same effect as implant, lasts 2-3 months
• Intrauterine device (IUD)


  Releases progesterone, T-shaped device inserted into uterus, lasts 5-10 years
• Non-hormonal contraception methods


  • Spermicides
  • Condoms
  • Diaphragms
  • Copper IUD
  • Sterilisation
  • Abstinence
• Spermicides


  Chemical methods that kill or disable sperm
• Condoms


  Barrier method worn over penis or placed in vagina, also prevent STDs
• Diaphragms


  Barrier method, plastic cup positioned over cervix, used with spermicide
• Copper IUD


  Kills sperm in uterus and prevents fertilised eggs implanting
• Sterilisation


  Surgical method of cutting and tying fallopian tubes or sperm duct, often permanent
• Abstinence


  Avoiding intercourse to ensure egg is not fertilised
• IVF treatment


  1. Mother given FSH and LH to encourage egg release and maturation

  2. Eggs extracted and fertilised in lab

  3. Embryos developed and one or two inserted into uterus
• IVF


  • Provides way for infertile couple to have child
  • Physically and emotionally stressful
  • Can lead to multiple births
  • Expensive if process needs to be repeated
• Homeostasis


  Maintenance of a constant internal environment despite internal and external changes
• Homeostasis is important to maintain enzyme action and all cell functions including growth, replication and controlled cell death
• Conditions homeostasis controls in the human body

  • Blood glucose concentration
  • Body temperature
  • Water levels
• Components of control systems involved in homeostasis

  • Receptors
  • Coordination centres
  • Effectors