Endocrine System

• The endocrine system works together with the nervous system to control vital bodily functions and maintain homeostasis consisting of several glands located throughout the body
• A gland is an organ which produces and release substances (hormones) that perform a specific function in the body
• Hormones are chemical messengers that are secreted directly into the blood, which are carried to organs and tissues of the body to exert their functions
• The pituitary gland is located in the brain and is referred to as the 'master gland' because its function is to control other hormones in the endocrine system; produces anti-diuretic hormone (vasopressin) which controls water balance and blood pressure
• The thyroid gland is located in the front of the neck and its function is the regulate the body's metabolic rate controlling the heart, muscle and digestive function, brain development and bone maintenance; produces thyroxine which regulates the body's metabolism
• The pineal gland is located deep in the brain and its function is to regulate sleep patterns; produces melatonin which releases at night to induce sleep
• The adrenal gland is situated on top of the kidneys and its function is to regulate the fight or flight response; composed of 2 distinct parts:

  1. Outer part- adrenal cortex releases cortisol, increasing energy levels
  2. Inner adrenal medulla produces adrenaline, responsible for regulating the stress response
• The pancreas makes digestive juices and produces hormones to control blood glucose levels; produces insulin which reduces glucose levels in the bloodstream and store it in kidneys as fat
• The ovaries are part of the female reproductive system and produces eggs and reproductive hormones; produces oestrogen which regulates the menstrual cycle
• The testes are part of the male reproductive system and produce sperm and maintain hormones; produces testosterone causing development of male characteristics such as growth of facial hair
• The sympathetic-adreno-medullar (SAM) axis concerns the adrenal medulla and release of adrenaline/ noradrenaline, having the effects of creating physiological (sympathetic) arousal and producing the fight or flight response
• The hypothalamic-pituitary-adrenal (HPA) axis concerns the adrenal cortex producing corticosteroids such as cortisol, helping the body to recover after stress but also have negative effects like reduced immune function
• SAM and HPA are triggered by a stressor but SAM is an instantaneous response, whereas HPA is much slower; HPA is harder to achieve and only activated in more extreme circumstances
• Sympathetic-Adreno-Medullar (SAM) Axis Changes:

  • Increased heart rate- increases blood flow to organs and increase movement of adrenaline around the body
  • Increased breathing rate- increases oxygen intake
  • Pupil dilation- increases light entry into the eye and enhance vision (especially in the dark)
  • Sweat production- regulates temperature
  • Reduction of non-essential functions- increases energy for other essential functions