B5 Adrenaline and Thyroxine (page 67) Flashcards
What is Adrenaline?
It is a hormone released by the adrenal glands, which are just above the kidneys (see page 62).
When is Adrenaline released
Adrenaline is released in response to stressful or scary situations - your brain detects fear or stress and sends nervous impulses to the adrenal glands, which respond by secreting adrenaline.
What do Adrenaline get the body ready for?
it gets the body ready for ‘fight or flight’ by triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscle.
For example, adrenaline increases heart rate.
What is Negative Feedback System?
Its is where your body can control the levels of hormones (and other substances) in the blood using negative feedback system.
When your body detects that the level of a substance has gone above or below the normal level, it triggers a response to bring the level back to normal again. (example - thyroxine).
What is Thyroxine?
It is a hormone released by the thyroid gland.
Where is the Thyroid Gland in the human body?
in the neck (see page 62).
What do the Thyroxine hormone do?
it plays an important role in regulating the basal metabolic rate - the speed at which chemical reactions in the body occur while the body is at rest.
Thyroxine is also important for loads of processes in the body, such as stiulating protein synthesis for growth and development.
When is Thyroxine released?
it is released in response to Thyroid Stimulating Hormone (TSH), which is released from the Pituitary Gland.
What system keeps the amount of Thyroxine in the blood at the right level?
A negative feedback System. - when the level of thyroxine in the blood is higher than normal, the secretion of TSH from the pituitary gland is inhibited (stopped). This reduces the amount of thyroxine released from the thyroid gland, so the level in the blood falls back towards normal.
Look at diagram on page 67.
(tip - you can think about negative feedback working like a thermostat - if the temperature gets too low, the thermostat will turn the heating on, then if the temperature gets too high, it’ll turn the heating off again).
Name the gland that releases thyroxine? (1 mark)?
Thyroid Gland (1 mark)
Describe the response if the level of thyroxine in the blood gets too high? (3 marks)
When the high level of thyroxine is detected the secretion of TSH from the pituitary gland is inhibited (1 mark). This reduces the amount of thyroxine released from the thyroid gland (1 mark), so the level in the blood falls back towards normal (1 mark)
