- Define hormone as a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver.
A hormone is a chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver
- State the role of the hormone adrenaline in the chemical control of metabolic activity, including increasing the blood glucose concentration and pulse rate.
Adrenaline is produced in a ‘fight or flight’ situation – when you are scared or excited, your body produces adrenaline. Adrenaline is secreted by the adrenal glands (there is one above each kidney) and is released into the blood so that it can travel to the appropriate target organs.
Adrenaline stimulates the heart to beat faster – the pulse rate increases. This means more blood (and thus, more oxygen) can be pumped around the body. It also stimulates the contraction of blood vessels in the skin and digestive system, so more blood is pumped to the muscles and the brain. This means they can respire faster, providing more energy to run or fight.
The liver is signalled to begin ‘gluconeogenesis’ too. This is the process of the production of glucose – either by breaking down glycogen (which is a storage polymer, made of many glucose molecules) or breaking down the lactic acid produced by muscles in exercise. This increases the blood glucose concentration. Because the body respires glucose to give energy, more glucose means more energy.
- Give examples of situations in which adrenaline secretion increases.
As previously mentioned, adrenaline is secreted in ‘fight or flight’ situations. Examples include writing an exam, being left alone in a horror house, riding a roller coaster, or realising that you wore your trousers backwards halfway through the school day. Not that I’m speaking from experience or anything.
Even better, if you’re desi, or really, from an Asian family, the true fear lies in being left alone with all your overly curious and nosy aunties and uncles. I’m sure you can think of your own fight or flight situations, though. 😉
- Compare nervous and hormonal control systems.
Notes submitted by Sarah.
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