hoomans

• Endocrine system

  Allows different parts of our body to communicate with each other
• Endocrine system

  Similar job to nervous system, but with lots of differences
• Endocrine system

  • Consists of a series of glands found throughout the body
  • Glands secrete hormones, which are small chemical molecules passed into the blood and spread throughout the body
• Hormones


  Act as signals to trigger certain changes inside cells
• Main glands in the endocrine system


  • Pituitary gland
  • Thyroid gland
  • Adrenal glands
  • Pancreas
  • Testes
  • Ovaries
• Pituitary gland

  Produces multiple hormones, some of which directly tell the body what to do and some which tell other glands to release their own hormones
• Thyroid gland

  Produces the hormone thyroxine, which relates to the rate of our metabolism and plays an important role in growth and development
• Pituitary gland detects low levels of thyroxine


  Releases thyroid stimulating hormone (TSH) to stimulate the thyroid to produce more thyroxine
• Adrenal glands

  Produce the hormone adrenaline, which is normally released during the fight-or-flight response
• Pancreas

  Produces the hormone insulin, which helps regulate blood glucose concentrations
• Testes

  Produce the hormone testosterone, which controls puberty, and produce sperm
• Ovaries

  Produce the hormone estrogen, which influences puberty and the menstrual cycle, and hold the female gametes (egg cells)
• Endocrine system vs. nervous system

  • Endocrine system uses hormones (small molecules secreted by glands and transported in the blood), while nervous system uses electrical impulses transferred along nerve cells
  • Hormones spread more slowly and have longer-lasting effects, while nerve impulses are sent very fast and have short-lasting effects
  • Hormones act more generally and interact with many different cells, while nerve impulses are sent to specific areas
• Puberty

  The period during which adolescents start to develop secondary sexual characteristics
• Secondary sexual characteristics

  • Facial hair in men
  • Breasts in women
• Reproductive hormones

  • Testosterone in men (produced in testes, stimulates sperm production)
  • Estrogen in women (produced in ovaries)
• Menstrual cycle

  1. Menstruation (uterus lining breakdown)

  2. Uterus lining build up

  3. Ovulation (egg release)

  4. Uterus lining maintenance
• Average menstrual cycle length is around 28 days but varies between people
• Menstruation

  Period of bleeding due to breakdown of uterus lining, lasts about 4 days
• Uterus lining build up

  Lasts around 10 days up to day 14, prepares for fertilized egg implantation
• Ovulation


  Egg released from ovary, occurs on a single day
• Uterus lining maintenance

  Lasts from day 14 to day 28, if no fertilized egg implants then lining breaks down and cycle repeats
• If a fertilized egg implants, the menstrual cycle stops as the woman is pregnant
• Estrogen

  Produced in ovaries, stimulates uterus lining growth
• Progesterone

  Produced in ovaries, maintains uterus lining
• Luteinizing hormone (LH)


  Produced in pituitary gland, stimulates egg release (ovulation)
• Follicle stimulating hormone (FSH)


  Produced in pituitary gland, stimulates egg maturation in ovaries
• FSH stimulates ovaries to produce estrogen


  As estrogen increases, it inhibits FSH (negative feedback)
• High estrogen levels

  Stimulate release of LH, causing ovulation
• Progesterone

  Inhibits both LH and FSH