L2.2.3: Stimuli for Control of Hormone Release

• STIMULI FOR CONTROL OF HORMONE RELEASE

  ● Hormone levels in the blood are maintained mostly by negative feedback mechanisms

  ○ A stimulus/low hormone levels in the blood trigger the release of more hormone

  ○ Hormone release stops once an appropriate level in the blood is reached
• 3 major categories of stimuli that activate endocrine glands

  • Hormonal
  • Humoral
  • Neural
• HORMONAL

  ● Most common

  ● Endocrine organs are activated by other hormones

  ● Example : Hormones of the hypothalamus stimulate the anterior pituitary to secrete its hormones
• HUMORAL

  ● Changing blood levels of certain ions and nutrients stimulate hormone release

  ● Humoral indicates various body fluids such as blood and bile

  ● Examples : Parathyroid hormone and calcitonin are produced in response to changing levels of blood calcium levels . Insulin is produced in response to changing levels of blood glucose
• NEURAL

  ● Nerve fibers stimulate hormone release

  ● Most are under the control of the sympathetic NS

  ● Example : Sympathetic stimulation of the adrenal medulla to release epinephrine and norepinephrine