The Role of Hormones: Basic (Edexcel IGCSE Science (Double Award))

Revision Note

Did this video help you?

The Role of Hormones: Basic

  • hormone is a chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs

    • They are chemicals that transmit information from one part of the organism to another and bring about a change

  • The following hormones are of great importance in humans:

    • Adrenaline

    • Insulin

    • Testosterone

    • Progesterone

    • Oestrogen

Adrenaline

  • Adrenaline is known as the 'fight or flight' hormone as it is produced in situations where the body may be in danger

  • It causes a range of different things to happen in the body, all designed to prepare it for movement (i.e. fight or flight)

  • These include:

    • An increase in heart rate and breathing rate - ensures glucose and oxygen can be delivered to muscle cells (and carbon dioxide can be taken away from muscles cells) at a faster rate

    • Diverting blood flow towards muscles and away from non-essential parts of the body such as the alimentary canal - ensures an increased supply of the reactants of respiration (glucose and oxygen)

    • Dilation of the blood vessels inside muscles - ensures more blood can circulate through them (again, supplying more glucose and oxygen)

    • Breaking down of stored glycogen to glucose in the liver and muscle cells, with glucose released by the liver being transported to active muscle cells - ensures a higher blood glucose concentration for increased respiration in muscle cells (providing greater energy for movement)

Insulin

  • Blood glucose concentration must be kept within a narrow range, so it’s another example of homeostasis (like the control of core body temperature)

    • Too high a level of glucose in the blood can lead to cells of the body losing water by osmosis, which can be dangerous

    • Too low a level of glucose in the blood can lead to the brain receiving insufficient glucose for respiration, potentially leading to a coma or even death

  • The pancreas and liver work together to control blood glucose levels

  • To carry out this role, the pancreas acts as an endocrine gland (making and secreting hormones into the bloodstream), although it also plays a vital (but separate) role in digestion (making and secreting enzymes into the digestive system)

  • If the blood glucose concentration gets too high:

    • Cells in the pancreas detect the increased blood glucose levels

    • The pancreas produces the hormone insulin, secreting it into the blood

    • Insulin stimulates muscles and the liver to take up glucose from the bloodstream and store it as glycogen (a polymer of glucose)

    • This reduces the concentration of glucose in the blood back to normal levels, at which point the pancreas stops secreting insulin

blood-glucose-insulin

The regulation of blood glucose levels

Testosterone

  • Testosterone is produced in the male testes

  • It is responsible for the development of secondary sexual characteristics in males

Progesterone

  • Progesterone is produced in the female ovaries

  • It is responsible for maintaining the uterine lining during pregnancy

Oestrogen

  • Oestrogen is produced by the female ovaries

  • It is responsible for the development of secondary sexual characteristics in females and regulating the menstrual cycle

Summary of hormones and their functions table

Hormone

Source

Role

Effect

Adrenaline

Adrenal gland

Readies the body for a 'fight or flight' response

Increases heart and breathing rate

Insulin

Pancreas

Lowers blood glucose levels

Causes excess glucose in the blood to be taken up by the muscles and liver and converted into glycogen for storage

Testosterone

Testes

Main sex hormone in males

Development of male reproductive organs and secondary sexual characteristics

Progesterone

Ovaries

Maintains pregnancy

Maintains the uterus lining to cushion the fertilised egg and allow it to develop

Oestrogen

Ovaries

Main sex hormone in females

Development of female secondary sexual characteristics and regulation of the menstrual cycle

Examiner Tips and Tricks

It is worth learning this list of effects of adrenaline on the body as it is a fairly common exam question and can be worth several easy marks.


You've read 0 of your 5 free revision notes this week

Sign up now. It’s free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Lára Marie McIvor

Author: Lára Marie McIvor

Expertise: Biology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

Download notes on The Role of Hormones: Basic