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• Cortisol production:

  1. Cortisol production is controlled by the hippocampus in the brain
  2. In response to stress the hippocampus sends impulses to the hypothalamus, which releases two hormones, corticotrophin-releasing hormone and arginine vasopressin.
  3. These 2 hormones stimulate the pituitary gland which responds by releasing the hormone adrenocorticotrophic hormone into the blood.
  4. When the cells of the adrenal glands take up this hormone, they release cortisol
• ANS + heart rate in exercise:

  • cardio-acceleratory centre is stimulated
  • nervous impulses travel along sympathetic nerve fibres to the sino-atrial node
  • the neurotransmitter noradrenaline is released
  • noradrenaline binds to cell membrane receptors on SAN cells
  • The SAN's electrical discharge increases in frequency
  • Heart rate increases
• ANS + heart rate in sleep:

  • cardio-inhibitory centre is stimulated
  • nervous impulses travel along parasympathetic nerve fibres to the SAN
  • the neurotransmitter acetylcholine is released
  • acetylcholine binds to cell membrane receptors on SAN cells
  • The SAN's electrical discharge decreases in frequency
  • heart rate decreases