5.4 - Hormonal Communication

Question 1

How does the hormonal system send information?

Answer 1

• As chemical signals

Question 2

What is the hormonal system made up of ?

Answer 2

glands and hormones

Question 3

What are endocrine glands ?

Answer 3

They are groups of cells that are specialised to secrete hormones. For example, pancreas secretes insulin

Question 4

What are hormones?

Answer 4

• Chemical messengers - many hormones are proteins or peptides. Eg insulin some hormones are steriodseg progesterone.

Question 5

How are hormones secreted ?

Answer 5

• By a change in concentration a a specific substance sometimes another hormone - thy can also be stimulated by electrical impulses.

Question 6

Where do hormones diffuse into?

Answer 6

• Directly through the bloodstream.

Question 7

Where do hormones bind to?

Answer 7

• They diffuse into the blood and bind to specific receptors for that hormone found on the membrane of some cells called target cells.
• tissues that contain target cells are called target tissue .
• the hormones trigger a response in the target cells
• the hormones trigger a response in target cells in effectors.

Question 8

An example of this:

Answer 8

_ Stimulus - e.g low blood glucose concentration
- Receptor - on pancreas cells detect the low blood glucose concentration.
- Hormone - The pancreas release the hormone glucagon into the blood
- Effectors- Target cells in the liver detect glucagon and convert glycogen into glucose.
- Response - Glucose is released into the blood, so glucose concentration increases

Question 9

Why is a hormone is called a first messenger ?

Answer 9

• A hormone is called a first messenger because it carries the chemical message the first part of the way, from the endocrine gland to the receptors on the target cells.

Question 10

What happens after hormone binds receptor on target cells ?

Answer 10

• When a hormone binds to its receptor it activates an enzyme in the cell membrane.
• The enzyme catalyses the production of a molecule inside the cell called a signalling molecule.
• This molecule signals to other parts of the cell to change how the cell works.
• The signalling molecule is called a second messenger
• Second messengers activate a cascade inside the cell

Question 11

What is an example of this - using adrenaline ?

Answer 11

• The hormone adrenaline is the first messenger.
• it binds to specific receptors in the cell membranes of many cells liver cells.
• when adrenaline binds it activates an enzyme in the membrane called adenylyl cyclase
• the activated ac catalyses the production os second messenger called cyclic AMP cAMP from ATP.
• cAMP activates a cascades Eg cascade of enzyme reactions make more glucose available to the cell by catalysing the breakdown of glycogen into glucose.

Question 12

What are adrenal glands?

Answer 12

• they are endocrine glands that are found just above your kidneys.
  -Each adrenal gland has an outer part called the cortex and inner part called medulla

Question 13

What is the role of the cortex in response to stress?

Answer 13

The cortex secretes steroid hormones, e.g. it secretes cortisol and aldosterone when you’re stressed.
These hormones have a role in both the short-term and the long-term responses to stress. Their effects include:
• stimulating the breakdown of proteins and fats into glucose. This increases the amount of energy available so the brain and muscles can respond to the situation.
• increasing blood volume and pressure by increasing the uptake of sodium ions and water by the kidneys.
• suppressing the immune system.

Question 14

What is the role of the medulla in response to stress?

Answer 14

The medulla secretes catecholamine hormones (modified amino acids), e.g. it secretes adrenaline and noradrenaline when you’re stressed. These act to make more energy available in the short-term by:
• increasing heart and breathing rate.
• causing cells to break down glycogen into glucose.
• constricting some blood vessels so that blood is diverted to the brain and muscles.

Question 15

What is an example of an endocrine gland and where is it found ?

Answer 15

• The pancreas
• It is found below the stomach

Question 16

What are the areas of the pancreas that contain endocrine tissue called and where are they found ?

Answer 16

-The islet of Langerhans
- They’re found in cluster around the blood capillaries

Question 17

What is the function of the IOL ?

Answer 17

• They secrete hormones directly into the blood.

Question 18

What two types of cells are they made up of ?

Answer 18

• Alpha and Beta cells

Question 19

What hormones do each of these cells secrete ?

Answer 19

Alpha - secrete a hormone called glucagon
Beta - secrete a hormone called insulin

Question 20

What do glucagon and insulin do ?

Answer 20

• It helps to control blood glucose concentration

Question 21

How would you identify endocrine tissue under a light microscope ?

Answer 21

• Purple - beta cells
• pink stained cells - alpha cells
• Islet of langerhans - paler patches

Question 22

How can you control blood glucose ?

Answer 22

• By eating and exercise
• Blood glucose concentration rises after eating food containing carbohydrate
• Blood glucose concentration falls after exercise as more glucose is used in respiration to release energy.

Question 23

What does insulin do ?

Answer 23

insulin lowers blood glucose concentration when it’s too high
1) Insulin binds to specific receptors on the cell membranes of liver cells and muscle cells.
2) It increases the permeability of cell membranes to glucose, so the cells take up more glucose.
3) Insulin also activates enzymes that convert glucose into glycogen.
4) Cells are able to store glycogen in their cytoplasm, as an energy source.
5) The process of forming glycogen from glucose is called glycogenesis.
6) Insulin also increases the rate of respiration of glucose, especially in muscle cells.

Question 24

What is glycogenesis ?

Answer 24

Making glycogen

Question 25

What does glucagon do ?

Answer 25

Glucagon raises blood glucose concentration when it’s too low
1) Glucagon binds to specific receptors on the cell membranes of liver cells.
2) Glucagon activates enzymes that break down glycogen into glucose.
3) The process of breaking down glycogen is called glycogenolysis.
Glucagon also promotes the formation of glucose from glycerol and amino acids.
5) The process of forming glucose from non-carbohydrates is called gluconeogenesis.
6) Glucagon decreases the rate of respiration of glucose in cells.

Question 26

What do beta cells do when they are depolarised ?

Answer 26

• ## Beta cells secrete insulin when they detect high blood glucose concentration1) When blood glucose concentration is high, more glucose enters the ß cells by facilitated diffusion.

2) More glucose in a B cell causes the rate of respiration to increase, making more ATP.

3) The rise in ATP triggers the potassium ion channels in the ß cell plasma membrane to close.

4) This means potassium ions (K*) can’t get through the membrane — so they build up inside the cell.

5) This makes the inside of the ß cell less negative because there are more positively-charged potassium ions inside the cell — so the plasma membrane of the ß cell is depolarised.

6) Depolarisation triggers calcium ion channels in the membrane to open, so calcium ions diffuse into the B cell.

7) This causes the vesicles to fuse with the ß cell plasma membrane, releasing insulin (by exocytosis).

Question 27

Why does diabetes occur ?

Answer 27

• This is when blood glucose concentration is not controlled

Question 28

What is type 1 diabetes ?

Answer 28

• It is an autoimmune disease, which body attacks and destroys B cells in the IOL
• This means they don’t produce any insulin
• After eating their blood glucose concentration stays high.
• The kidneys can’t reabsorb all this glucose , so some of its excreted in the urine.
• Usually develops in children and young adults
• Risk is slightly increased if there’s a close family history of the disease.

Question 29

How to treat type 1 diabetes ?

Answer 29

• Treated with insulin therapy
• Most people with type 1 diabetes need regular insulin injections throughout the day
• Some people use an insulin pump
  -Some people have islet cells transplantation - they receive healthy islet cells from a donor so their pancreas can produce some insulin.
• Diet , activity

Question 30

What is Type 2 diabetes ?

Answer 30

• Occurs when the beta cells don’t produce enough insulin or when body cells don’t respond properly to insulin.
• blood glucose is higher than normal
• acquired later in life
• often linked with obesity
  -increased in certain ethnic groups - African , Asian
• risk with close family history.

Question 31

What is the treatment of type 2 diabetes ?

Answer 31

• It is initially managed through lifestyle changes.
• Eating a balanced healthy diet, getting regular exercise and losing weight if needed can help prevent the onset of type 2 diabetes as well as controlling he effects.
• Medication
• Metformin - first med prescribed acts on liver cells to reduce amount of glucose that they release into the blood. It also acts to increase the sensitivity of insulin so more insulin can be taken up with the same amount of insulin.
• Sulfonylureas - These stimulate the pancreas to produce more insulin.
• Thiazolidinediones - These also make the body cells more sensitive to insulin.
• Insulin therapy

Question 32

How can insulin be produced ?

Answer 32

• Insulin can be produced by genetically modified bacteria.
• Insulin is used to be extracted from animal pancreases (pigs and cattle ) to treat people with type 1 diabetes
• But nowadays, human insulin can be made by genetically modified bacteria
• Producing insulin using GM bacteria is cheaper than extracting it from animal pancreases
• Larger quantities of insulin can be produced using GM bacteria
• This is more effective then pig or cattle insulin as its less likely to trigger an allergic response or be rejected by the immune system
• Some people prefer insulin from GM bacteria for ethical or religious reasons.

Question 33

How can stem cells be used to cure diabetes ?

Answer 33

• Stem cells could be grown into B cells
• the b cells would then be implanted into the pancreas of a person with type1 diabetes
• this means the person would be able to make insulin as normal
• this treatment is still being developed