topic 7 bio

• Hormones

  Chemical messengers sent around the body by the endocrine system
• Endocrine system


  • Sends hormones directly into the bloodstream
  • Made up of glands that secrete hormones
• Endocrine glands

  • 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
• 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 development of female secondary sexual characteristics
• Testes

  Secrete testosterone and are involved in the production of sperm and 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
• Aspects of the 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 that controls thyroxine levels
• The menstrual cycle is the process the body undergoes each month to prepare for a potential pregnancy
• Events of the menstrual cycle

  1. Uterine lining breaks down and woman has period

  2. Lining builds up again

  3. Ovulation occurs - egg released from ovary

  4. If egg not fertilised, lining begins to break down and cycle continues
• 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 growth of uterine lining
• Luteinising hormone (LH)

  Its release results in ovulation
• Progesterone


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

  • Contraceptive pill (mixed and progesterone only)
  • Contraceptive patch
  • Contraceptive implant
  • Contraceptive injection
  • Intrauterine device (IUD)
• Mixed contraceptive pill


  Contains oestrogen and progesterone to inhibit FSH and prevent egg maturation, thicken cervical mucus and stop uterine lining developing
• Progesterone only contraceptive


  Has less side effects than mixed pill
• 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
• Intrauterine device (IUD)


  Releases progesterone, same effect as implant
• Non-hormonal contraception methods

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

  Kill or disable sperm
• Condoms

  Worn over penis or placed in vagina to prevent sperm fertilising egg and prevent STDs
• Diaphragm

  Plastic cup positioned over cervix, used with spermicide
• Copper IUD

  Kills sperm in uterus and stops fertilised eggs implanting
• Sterilisation

  Surgical procedure to cut and tie fallopian tubes or sperm duct, often permanent
• Abstinence

  Avoiding intercourse to ensure egg is not fertilised
• IVF

  In vitro fertilisation - eggs extracted from mother, fertilised in lab and embryos inserted into uterus
• Fertility drugs used in IVF

  • FSH
  • LH
  • Clomiphene
• Homeostasis

  Maintenance of a constant internal environment
• Homeostasis is important to maintain enzyme action and all cell functions including growth, replication and controlled cell death