5.9 Endocrine System

Question 1

What does the endocrine system consist of?

Answer 1

A series of glands which all secrete hormones that are found within the body. Hormones are small chemical molecules that are passed into the blood and then spread throughout the body in the blood stream. This allows the hormones to come into contact with a wide range of tissues. Some of these tissues will have receptors that are specific to the hormones and so the hormone molecules act as signals and trigger certain changes within the cells.

Question 2

What does the pituitary gland do?

Answer 2

It produces multiple different hormones; some of which directly tell the body what to do and some, which tell other glands to release their hormones.

Question 3

What gland is found in the neck?

Answer 3

Thyroid gland

Question 4

What does the thyroid gland do?

Answer 4

Produces the hormone thyroxine. This regulates the rate of metabolism and also plays an important role in growth and development.

Question 5

What hormone does the pituitary gland release that effects the thyroid gland and why?

Answer 5

Thyroid stimulating hormone or TSH. If the pituitary gland detects low levels of thyroxine, it will release TSH which stimulates the thyroid to produce more thyroxine. This will bring the level of thyroxine back up to normal.

Question 6

Describe how the negative feedback system keeps the amount of thyroxine in the blood at the right level

Answer 6

When the level of thyroxine in the blood is higher than normal, the secretion of TSH from the pituitary gland is inhibited. This reduces the amount of thyroxine released from the thyroid gland so the level in the blood falls back towards normal. When the level of thyroxine is lower than usual, the pituitary gland is stimulated to release TSH. This increases the amount of thyroxine released from the thyroid gland so the level of thyroxine is back to normal.

Question 7

What are the glands that sit on top of the kidneys?

Answer 7

Adrenal glands

Question 8

What hormone do the adrenal glands release?

Answer 8

Adrenaline

Question 9

Describe how adrenaline prepares you ‘Fight or Flight’

Answer 9

Adrenaline prepares the body for ‘flight or fight’ - it does this by activating processes that increase the supply of oxygen and glucose to cells. For example:
1) Adrenaline binds to specific receptors in the heart. This causes the heart muscle (the effector) to contract more frequently and with more force, so heart rate and blood pressure increase.
2) This increases blood flow to the muscles, so the cells receive more oxygen and glucose for increased respiration.
3) Adrenaline also binds to receptors in the liver. This causes the liver to break down its glycogen stores to release glucose.
4) This increases the blood glucose level, so there’s more glucose in the blood to be transported to the cells.

Question 10

What happens in the endocrine system when your brain detects a stressful situation?

Answer 10

When your brain detects a stressful situation, it sends nervous impulses to the adrenal glands, which respond by secreting adrenaline. This gets the body ready for action.

Question 11

What hormone does the pancreas produce?

Answer 11

Insulin

Question 12

What does insulin do?

Answer 12

It helps us to regulate our blood glucose concentrations

Question 13

What hormone do the testes produce?

Answer 13

Testosterone

Question 14

What are the two main jobs of the testes?

Answer 14

1) Producing the hormone testosterone, which controls puberty.
2) Producing the male gametes, sperm, for reproduction.

Question 15

What hormone do the ovaries release?

Answer 15

Oestrogen

Question 16

What are the two main jobs of the ovaries?

Answer 16

1) Producing oestrogen, which influences puberty and the menstrual cycle
2) They hold the female gametes, egg cells

Question 17

How does the endocrine system differ from the nervous system?

Answer 17

• The endocrine system relies on hormones, which are small molecules secreted by glands and transported in the blood. This means that hormones spread more slowly and the effects last longer.
• The nervous system relies mainly on electrical impulses which are transported along nerve cells. This means that nerve impulses are very fast and the effects don’t last very long.
• Hormones act more generally. They spread throughout the entire body which means they interact with a lot of different cells.
• Nerve impulses are sent to one specific area, such as the particular muscle that we need to move our arm. We often describe the nervous system as being ‘precise’