The Endocrine System

• The Endocrine System- a system of different glands & ducts throughout the body.
• Each gland in the Endocrine System secretes a specific type of hormone directly into the bloodstream to regulate the cells and tissues of the body.
• The Endocrine System is controlled by an area of the brain called the hypothalamus.
• 1. The hypothalamus receives sensory information about the internal & external environment and decides how to respond.
• The Autonomic nervous system controls automatic processes within the body through nerves straight to the organs or by stimulating the endocrine system.
• 2. The hypothalamus sends a releasing hormone to activate the pituitary gland.
• 3. The pituitary gland releases an activating hormone into the bloodstream which signals to the target gland to release its hormone.
• 4. This system= feedback loop, increasing levels of hormone is detected by hypothalamus which then shuts down the secretion of its releasing hormone, which then shuts down the rest of the system.
• Hormones= chemicals that are detected by 'target' organs and influence their function.
• A physiological reaction occurs when enough receptor sites are stimulated by a hormone.
• Examples of endocrine controlled responses:

  1. Circadian rhythm (sleep-wake cycle)
  2. The Menstrual Cycle
  3. The fight or flight response
• Acute Stressors:

  • require immediate response
  • response system takes milliseconds to activate
• Chronic Stressors:

  • require prolonged response (sometimes months/ years)
  • response system is slower and is about making energy last
• Two pathways to respond to stress:

  • Acute stress- nervous system (SAM)
  • Chronic stress- endocrine system (HPA)
• Acute stress- The Sympatho-Adrenal Medullary Pathway

  1. A stressor is detected by the amygdala and the hypothalamus activates the Autonomic Nervous System
  2. S- sympathetic nervous system, controls arousal
  3. A-nerves from the SNS stimulate the adrenal glands
  4. M- the centre of the adrenal glands is called the adrenal medulla, and it releases adrenaline into the bloodstream
  5. This hormone can stimulate the fight or flight reactions throughout the body
• Effect of adrenaline:

  • Eyes- pupils dilate
  • Heart- heart rate & blood pressure increases
  • Digestion suppressed- butterflies/ feel sick
  • Muscle tension increases- can cause shaking
  • When the threat has passed, Parasympathetic nervous system kicks in (rest and digest- everything is reversed)
• Acute stress- travels through neurons & about quick release in energy.
• Chronic stress- hormones that travel through the blood.