The Endocrine System

• The Endocrine System:

  • The endocrine system works alongside the nervous system to control vital functions in the body.
  • Acts more slowly than the nervous system but has very widespread and powerful effects.
• Glands and Hormones:

  • Various glands in the body, such as the thyroid gland, produce hormones.
  • Hormones are secreted into the bloodstream and affect any cell in the body that has a receptor for that particular hormone.
  • Most hormones affect cells in more that one body organ, leading to many diverse and powerful responses.
• Glands and Hormones:

  • Pituitary - Thyroxine - increases heart rate, metabolic rates and affects growth rates.
  • Pancreas - Insulin - breaks down sugar levels.
  • Adrenal - adrenaline - gets body ready for fight or flight.
• Fight or Flight: (1)

  • Endocrine system and ANS work in parallel to each other e.g during a stressful event.
  • When a stressor is perceived your hypothalamus (part of your brain) activates the pituitary gland and this triggers activity in the sympathetic branch of the ANS.
  • The ANS changes from its usual resting state (parasympathetic state) to the physiologically arousal sympathetic state.
• Fight or Flight: (2)

  Adrenaline

  • Adrenaline (stress hormone) is released from the adrenal medulla (part of the adrenal gland) into the bloodstream.
  • This triggers physiological changes in the body (increase in heart rate, breathing increases, pupils dilate, digestion stops).
  • This creates physiological arousal necessary for the fight or flight.
• Fight or Flight: (3)

  Immediate and Automatic

  • This all happens in an instant as soon as the threat is detected.
  • This is an acute response and an automatic reaction in the body.
  • The changes explain why stress, panic or excitement, are often experienced as a ‘sick’ feeling.
• Fight or Flight: (3)

  Sympathetic state

  • Increases heart rate.
  • Increases breathing rate.
  • Dilates pupils.
  • Inhibits digestion.
  • Inhibits saliva production.
  • Contracts rectum.
• Fight or Flight: (3)

  Parasympathetic state

  • Decreases heart rate.
  • Decreases breathing rate.
  • Constricts pupils.
  • Stimulates digestion.
  • Stimulates saliva production.
  • Relaxes rectum.
• Fight or Flight: (4)

  Parasympathetic action

  • Finally, once the threat has passed, the parasympathetic nervous system returns the body back to its resting state.
  • The parasympathetic branch of the ANS works in opposition to the sympathetic system.
  • The parasympathetic system acts as a ‘brake’ and reduced the activities of the body that were increased by the actions of the sympathetic branch.
  • Sometimes referred to as the rest and digest response.