B5.3

• What are hormones?

  Chemical messengers secreted from glands
• How do hormones transport messages in the body?

  Via the blood to target organs
• What is the role of cell surface receptors in hormone action?

  They bind hormones to initiate responses
• Which hormone controls body metabolism?

  Thyroxine
• Where is thyroxine produced?

  In the thyroid gland
• What physiological response does adrenaline initiate?

  The fight or flight response
• What effects does adrenaline have on the heart and breathing rate?

  It increases both heart and breathing rate
• How does adrenaline affect blood flow in the body?

  It increases blood flow to muscles and decreases blood flow to the digestive system
• What process occurs in the liver when adrenaline is released?

  The breakdown of glycogen into glucose
• Why is the breakdown of glycogen into glucose important during a stress response?

  It allows for more ATP production and muscle contraction
• What is negative feedback in the context of homeostasis?

  A response that restores conditions when they change from their normal point
• What is an example of a negative feedback system in the body?

  The secretion of TSH by the pituitary gland
• What happens when elevated thyroxine is detected in the hypothalamus?

  It signals the pituitary gland to stop secreting TSH
• What is the role of TSH in relation to thyroxine production?

  It stimulates the thyroid gland to secrete thyroxine
• How does negative feedback help maintain homeostasis in the body?

  By restoring conditions to their normal point when changes occur