endocrine system

• Endocrine system


  Composed of glands that secrete chemicals called hormones directly into the bloodstream
• Hormones


  Chemicals secreted by glands that circulate in the bloodstream and affect target cells/organs
• Compared to the nervous system


  The effects of hormones are slower but they act for longer
• Important structures in the endocrine system

  • Pituitary gland
  • Pancreas
  • Thyroid
  • Adrenal glands
  • Ovaries (females)
  • Testes (males)
• Pituitary gland


  The 'master gland' making hormones e.g. Follicle Stimulating Hormone
• Pancreas


  Produces insulin which regulates the blood glucose level
• Thyroid


  Produces thyroxine which controls the metabolic rate and affects growth
• Adrenal glands


  Produce adrenaline
• Ovaries (females)


  Produce estrogen
• Testes (males)


  Produce testosterone
• The major endocrine glands in the body secrete hormones which circulate around the body in the bloodstream
• Pituitary gland


  A 'master gland' which secretes several hormones into the blood in response to body conditions
• How pituitary gland hormones work

  1. Pituitary gland makes and secretes hormones

  2. Hormones act on other glands to stimulate other hormones

  3. This brings about effects
• Hormones


  Synthesized and released into the bloodstream from a gland, circulate in the bloodstream, and have an effect on target cells
• Endocrine glands


  Synthesise substances such as hormones and release them into the bloodstream
• Hormones


  Chemical substances that circulate in the bloodstream and only affect target organs, produced in large quantities and can be very powerful, control ongoing internal functions and enable bodies to react to environmental changes
• Pituitary gland


  Often referred to as the 'master gland' because it controls the production and release of other hormones from other glands in the endocrine system, controlled by the hypothalamus
• Anterior lobe of pituitary gland

  Releases adrenocortical trophic hormone (ACTH), which stimulates the adrenal cortex and the release of cortisol
• Posterior lobe of pituitary gland

  Releases oxytocin, which is responsible for uterus contractions during childbirth and regulates emotional responses and pro-social behaviours
• Pineal gland


  Releases melatonin which is responsible for important biological rhythms, including the sleep-wake cycle, influenced by light-dark cycle
• Thyroid gland


  Plays a role in controlling heart, muscle and digestive function, brain development and bone maintenance, releases thyroxine which regulates metabolism
• Pancreas


  Plays a significant role in digestion by producing enzymes to break down food and hormones to help regulate blood-sugar levels and appetite, main hormone is insulin which helps break down glucose
• Adrenal gland


  Divided into adrenal medulla and adrenal cortex, adrenal medulla releases adrenaline and noradrenalin for 'fight or flight' response, adrenal cortex releases cortisol which stimulates glucose release and suppresses immune system
• Testes


  Release androgens including testosterone, responsible for development of male sex characteristics during puberty
• Ovaries


  Release oestrogen which controls regulation of female reproductive system, including menstrual cycle and pregnancy
• Questions about glands and hormones will tend to ask for identification of the gland, along with a description or outline of the hormone it produces, and how it impacts behaviours
• Jaren is visiting the doctor for their yearly check-up. The doctor mentions that they will conduct a full examination, including tests focused on key parts of their endocrine system.
• Describe the function of the endocrine system, using at least two examples of glands and hormones

  1. Regulate organ activity within the body by secreting hormones into the bloodstream

  2. When hormone reaches target organ, it produces necessary effect

  3. Two examples: Adrenal glands > adrenaline, Pancreas > insulin
• Adrenaline is a hormone produced by the adrenal medulla that prepares the body for the 'fight or flight' response
• How adrenaline works


  1. Neurons of sympathetic nervous system stimulate adrenal medulla to secrete adrenaline

  2. Adrenaline binds to receptors on target organs

  3. Increases heart rate to supply more blood, oxygen and glucose to muscle cells

  4. Stimulates cardiovascular control centre to further increase heart rate

  5. Constricts blood vessels to less important organs to divert more blood to organs involved in 'fight or flight'