- 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
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.
- Describe adrenaline as the hormone secreted in ‘fight or flight’ situations and its effects, limited to increased breathing and pulse rate and widened pupils
Adrenaline is produced in a ‘fight or flight’ situation – when you are scared or excited, your body produces adrenaline. Adrenaline is secreted from 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 muscles that control your breathing to increase your breathing rate. This allows your blood to absorb more oxygen and helps the body expel more carbon dioxide. Both of these outcomes are useful because it means our body tissues are provided with more oxygen and can respire faster, giving us more energy to deal with whatever situation put us in ‘fight or flight’ mode.
- 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, public speaking, being left alone in a horror house, riding a roller coaster, or being the last person left in the family version of the game bulldog. The horror.
Even better, if you’re desi, or really, from any 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. 😉
- Discuss the role of the hormone adrenaline in the chemical control of metabolic activity, including increasing the blood glucose concentration and pulse rate
As previously explained, 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 deal with whatever put you in ‘fight or flight’ mode.
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.
- Compare nervous and hormonal control system in terms of speed and longevity of action
While we tackle this learning objective, I figured I might as well make a table that compares the nervous and endocrine system as a whole:
Notes submitted by Sarah
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