The Endocrine System

• What is the definition of the endocrine system?


  A chemical system of communication that instructs glands to release hormones directly into the bloodstream
• What are glands?


  Organs in the body that produce and secrete hormones
• What are hormones?


  Chemicals that circulate in the bloodstream and influence target organs to regulate bodily activity
• What is the role of the pituitary gland?


  It is the master gland that controls and stimulates the release of other hormones in the endocrine system
• How is the pituitary gland divided?


  It is divided into the anterior (front) and posterior (rear) lobes
• What hormone does the anterior lobe of the pituitary gland release?

  ACTH
• What is the function of ACTH?


  It stimulates the adrenal cortex and the release of cortisol during the stress response
• What hormone does the posterior lobe of the pituitary gland release?


  Oxytocin
• What is the role of oxytocin?


  It is responsible for uterus contractions during childbirth
• Which part of the brain controls the pituitary gland?


  The hypothalamus
• What hormone does the pineal gland release?


  Melatonin
• What is the function of melatonin?


  It is responsible for important biological rhythms, including the sleep-wake cycle
• What are the two parts of the adrenal gland?


  The adrenal medulla and adrenal cortex
• What does the adrenal medulla release?


  Adrenaline and noradrenaline
• What is the role of adrenaline and noradrenaline?


  They play an important role in the ‘fight or flight response’
• What does the adrenal cortex release?


  Cortisol
• What is the function of cortisol?


  It stimulates the release of glucose for energy while suppressing the immune system
• What do the testes release?


  Androgens, including testosterone
• What is the role of testosterone?


  It is responsible for the development of male sex characteristics during puberty and promotes muscle growth
• What hormone do the ovaries release?

  Oestrogen
• What is the function of oestrogen?


  It controls the regulation of the female reproductive system, including the menstrual cycle and pregnancy
• Fight or Flight Response - Step 1: A


  Person enters a stressful/dangerous situation (acute stressor)
• Flight or Flight Response - Step 2: H


  Amygdala activated which send a distress signal to the hypothalamus
• Flight or Flight Response - Step 3: S

  Hypothalamus activates SAM pathway
• Flight or Flight Response - Step 4: A


  Stimulates the adrenal medulla which releases adrenaline and noradrenaline
• Fight or Flight Response - Step 5: F


  Adrenaline causes psychological changes which help the body prepare for fight or flight
• Fight or Flight Response - Step 6: P


  Causes physiological reactions
• Role of adrenaline and noradrenaline


  • Increased blood flow to the brain and skeletal muscles - for quick thinking and reactions
  • Decreased blood flow to systems that are not time critical such as the skin and the digestive and immune systems
  • Dilated pupils for improved vision and faster breathing rate for increased oxygen in the blood - increased sweat to remove heat
  • Psychological effects of increased anxiety, attention and increased alertness
• Fight or Flight Response AO3 - Not a full explanation


  • Fight or flight response is not only response - some suggest that humans engage in an initial ‘freeze’ response
  • Gray suggests that the first response to danger is to avoid confrontation altogether, which is demonstrated by a freeze response
  • During the freeze response animals and humans are hyper-vigilant
  • This is another explanation for the fight or flight response which weakens the explanation as it is not a full explanation
• Fight or Flight AO3 - Beta Bias


  • Fight or flight response is typically a male response to danger and more recent research suggests that females adopt a ‘tend and befriend’ response instead
  • According to Taylor et al women are more likely to protect their offspring and form alliances with other women
  • Early research was typically conducted on males (androcentrism) and consequently researches assumed that the findings could be generalised to females
  • Highlights a beta bias within this area of psychology as psychologists assumed that females responded in the same way as males
• Fight or Flight AO3 - Genetic basis for gender difference

  • Lee and Harley, found that the SRY gene (found only on the Y chromosome in males) directs male development by promoting aggression and resulting in the fight or flight response
  • Suggested the SRY gene may prime males to respond in this way by the release of hormones like adrenaline
  • Absence of the gene in females, may prevent this stress response and instead promote ‘tend and befriend’
  • This is a further example of how the fight or flight response is not the exclusive response to a stressful situation