The Endocrine System

1. 1 State [1 mark]

   State what is meant by a hormone.

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   Model answer

   A chemical messenger that is made in a gland and carried in the blood to a target organ.

   Mark scheme

   • Chemical messenger made in a gland, carried in the blood — 1 mark
2. 2 Name [3 marks]

   Name the gland that releases each of these hormones: insulin, thyroxine and testosterone.

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   Model answer

   Insulin is released by the pancreas. Thyroxine is released by the thyroid gland. Testosterone is released by the testes.

   Mark scheme

   • Pancreas — 1 mark
   • Thyroid gland — 1 mark
   • Testes — 1 mark
3. 3 Explain [3 marks]

   Explain why a hormone that is released into the blood only affects its target organs.

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   Model answer

   The hormone is carried to every part of the body. Only cells in the target organs have the receptors that the hormone can bind to, so only those cells respond to it.

   Mark scheme

   • Carried everywhere in the blood — 1 mark
   • Only target cells have receptors — 1 mark
   • Only those cells respond — 1 mark
4. 4 Describe [3 marks]

   Describe three differences between the endocrine system and the nervous system.

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   Model answer

   The endocrine system uses chemicals carried in the blood, but the nervous system uses electrical impulses along neurones. Hormones act more slowly than nerve impulses. The effects of hormones last longer than the effects of nerve impulses.

   Mark scheme

   • Chemicals and electrical impulses — 1 mark
   • Slower and faster — 1 mark
   • Longer lasting and short-lived — 1 mark
5. 5 Explain [4 marks]

   A person's blood glucose level is too high after a meal. Describe how the endocrine system could respond to this, naming the gland and the hormone.

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   Model answer

   The pancreas detects the high glucose, and releases the hormone insulin into the blood. The insulin is carried to the liver and muscles, which are the target organs, and makes them take up glucose, so the blood glucose falls.

   Mark scheme

   • Pancreas releases insulin — 1 mark
   • Carried in the blood — 1 mark
   • Target organs are the liver and muscles — 1 mark
   • Glucose falls — 1 mark
6. 6 Evaluate [6 marks]

   Explain why the pituitary gland is sometimes called the master gland, and discuss why it is useful to have both a nervous system and an endocrine system.

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   Model answer

   The pituitary gland releases hormones that control other endocrine glands. For example, it releases TSH, which makes the thyroid gland release thyroxine, and FSH and LH, which act on the ovaries. So it controls the activity of many other glands. Having both systems is useful because the nervous system gives fast responses, such as pulling a hand away from a hot object, which protects the body quickly, and the response is short-lived. The endocrine system gives slower responses, which last for longer, such as growth, the control of blood glucose and reproduction, which need to be controlled over minutes, hours or years. The two systems work together, and the body needs both kinds of response.

   Mark scheme

   • Pituitary releases hormones that control other glands — 1 mark
   • Example such as TSH or FSH — 1 mark
   • Nervous system is fast and short-lived — 1 mark
   • Example of a nervous response — 1 mark
   • Endocrine system is slower and longer lasting — 1 mark
   • Example of a hormonal response, and a conclusion — 1 mark

Quick check

1. 1

   Which gland is called the master gland?

   1. AThyroid
   2. BPancreas
   3. CPituitary
   4. DAdrenal
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   C: Pituitary

   The pituitary gland controls other glands.

2. 2

   How do hormones travel around the body?

   1. AIn the nerves
   2. BIn the blood
   3. CIn the air
   4. DIn the bones
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   B: In the blood

   In the blood.

3. 3

   Which gland releases insulin?

   1. APancreas
   2. BThyroid
   3. CPituitary
   4. DOvary
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   A: Pancreas

   The pancreas.

4. 4

   Which hormone is released by the ovaries?

   1. AInsulin
   2. BThyroxine
   3. CAdrenaline
   4. DOestrogen
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   D: Oestrogen

   Oestrogen.

5. 5

   What is a target organ?

   1. AThe gland that makes the hormone
   2. BAn organ that responds to a hormone
   3. CA tube that carries the hormone
   4. DA cell that makes hormones
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   B: An organ that responds to a hormone

   An organ that has receptors for the hormone and responds to it.

6. 6

   Which gland is on top of each kidney?

   1. AThyroid glands
   2. BPituitary glands
   3. CAdrenal glands
   4. DSalivary glands
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   C: Adrenal glands

   The adrenal glands.

7. 7

   Which statement about the endocrine system is correct?

   1. AIts effects are slower and longer lasting than those of nerves
   2. BIt uses electrical impulses
   3. CIt only works on one cell
   4. DIt is faster than the nervous system
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   A: Its effects are slower and longer lasting than those of nerves

   The effects are slower and longer lasting than those of nerves.

8. 8

   Which hormone controls the metabolic rate?

   1. AInsulin
   2. BAdrenaline
   3. CTestosterone
   4. DThyroxine
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   D: Thyroxine

   Thyroxine, from the thyroid gland.

9. 9

   A hormone reaches all parts of the body, but only the liver responds. What explains this?

   1. AOnly the liver is connected to the blood
   2. BOnly liver cells have receptors for it
   3. CThe hormone is made in the liver
   4. DThe hormone is destroyed in other organs
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   B: Only liver cells have receptors for it

   Only liver cells have the receptors for the hormone.