Hormone pathway: Adrenaline

• Adrenaline and Noradrenaline - Hormones and neurotransmitters in the body’s ‘fight or flight’ response
• Adrenaline and noradrenaline primarily operate through the sympathetic nervous system and do not  have a classic negative feedback loop like some hormones 
• Stimulus: Perceived threat 
• Hypothalamus: triggers the sympathetic nervous system
• Adrenal Glands: secrete adrenaline into the bloodstream. Adrenaline bonds to adrenergic receptors on target cells 
• Adrenal medulla and Sympathetic nerve endings: release noradrenaline
• Heart rate increases: stimulates beta-1 receptors in the heart, boosting heart rate and contractility 
• Airway Dilation: Activates beta-2 receptors in the lungs, relaxing bronchial muscles for better airflow
• Glucose Release: promotes glycogen breakdown in the liver, increasing blood glucose levels for energy 
• Blood flow redistribution: constricts blood vessels in non essential areas, redirecting blood to muscles and vital organs
• Pupil dilation: Activates muscles in the eyes, increasing light energy and enhancing vision
• Deactivation of stress response: 

  • Once the perceived threat is gone, the parasympathetic nervous system reduces the ‘fight or flight response 
  • Adrenaline and noradrenaline is quickly reabsorbed by nerve endings or broken down by enzymes 
  • Heart rate, blood pressure and other physiological effects return to normal as levels decrease