Hormonal Communication

Question 1

Define endocrine gland

Answer 1

Group of specialised cells which secrete hormones

Question 2

Define exocrine gland

Answer 2

Group of specialised cells which secrete chemicals through ducts into organs or to the surface of the body

Question 3

Define hormone

Answer 3

Chemical messengers which travel around the body in the bloodstream

Question 4

Define target tissue

Answer 4

Specific cells that hormones act on to stimulate a response

Question 5

List 8 endocrine glands, the hormone they secrete and the general role of each hormone.

Answer 5

1. Pituitary gland (In brain)- growth hormone, anti-diuretic hormone and gonadotrophins (control development of ovaries and testes.
2. Pineal gland (brain)- melatonin (affects reproductive development and daily cycles)
3. Thyroid gland (neck)- thyroxine (controls rate of metabolism and rate that glucose is used up in respiration and promotes growth)
4. Adrenal gland (above kidney)- adrenaline (increases heart and breathing rate and raises blood-sugar level)
5. Testis- produces testosterone (controls sperm production and secondary sexual characteristics)
6. Thymus (chest)- thymosin (promotes production and maturation of white blood cells)
7. Pancreas (stomach area)- insulin (converts excess glucose into glycogen in the liver) and glucagon (converts glycogen back to glucose in the liver)
8. Ovary- oestrogen (controls ovulation and secondary sexual characteristics),and progesterone, (which controls ovulation and secondary sexual characteristics and prepares the uterus lining for receiving an embryo)

Question 6

Describe how hormonal communication occurs.

Answer 6

1. Hormones are secretes into the blood when a gland is stimulated.
2. Once secreted, the hormones are transported in the blood plasma all over the body.
3. The hormones diffuse out of the blood and bind to specific receptors for the hormone, found on the membranes, or in the cytoplasm of cells in the target organs.- target cells
4. Once bound to their receptors the hormones stimulate the target cells to produce a response

Question 7

State the location of the adrenal glands in the body and describe their structure.

Answer 7

1. Two small glands that are located on top of each kidney and are made up of two distinct parts surrounded by a capsule.
2. The adrenal cortex- the outer region of the glands, produces hormones vital to life e.g. cortisol and aldosterone
3. The adrenal medulla- the inner region of the glands. This produces non-essential hormones, such as adrenaline which helps the body react to stress.

Question 8

Describe the role of the adrenal cortex and the hormones produced by it.

Answer 8

Production of hormones by adrenal cortex is controlled by hormones released from the pituitary gland in the brain. 
3 main types of hormones:
1. Glucocorticoids
2. Mineralocorticoids
3.Androgens

Question 9

Describe the function of glucocorticoids

Answer 9

The release of these hormones from the adrenal cortex is controlled by the hypothalamus

1. Include cortisol which helps regulate metabolism by controlling how the body converts fats, proteins, and carbs to energy.
2. It also helps regulate blood pressure and cardiovascular function in response to stress
3. Another glucocorticoid hormone released is corticosterone. This works with cortisol to regulate the immune response and suppress inflammatory reactions

Question 10

Describe the function of mineralocorticoids

Answer 10

Release from adrenal cortex is mediated by signals triggered by the kidney
1. Main one is aldosterone- helps control blood pressure by maintaining the balance between salt and water concentrations in the blood and body fluids.

Question 11

Describe the function of androgens

Answer 11

1. Small amounts of male and female sex hormones are released
2. Small impact compared to main sex hormones but still important

Question 12

Describe the role of the adrenal medulla and the functions of the hormones produced.

Answer 12

Released when the sympathetic nervous system is stimulated. This occurs when the body is stressed
Two hormones secreted by medulla:
1. Adrenaline
2. Noradrenaline

Question 13

Describe the function of adrenaline

Answer 13

1. This increases the heart rate sending blood quickly to the muscles and brain.
2. It also rapidly raises blood glucose concentration levels by converting glycogen to glucose in the liver

Question 14

Describe the function of noradrenaline

Answer 14

1. Works with adrenaline in response to stress, producing effects such as increased heart rate, widening of pupils, widening of air passages and the narrowing of blood vessels in non-essential organs

Question 15

Define histology

Answer 15

The study of the microscopic structure of tissues.

Question 16

Describe the roles of the pancreas.

Answer 16

Two main functions:

1. Exocrine gland- to produce enzymes and release them via a duct into the duodenum
2. Endocrine gland- to produce hormones and release them into the blood

Question 17

What is the role of the pancreas as an exocrine gland

Answer 17

1. Most of pancreas is made up of exocrine glandular tissue
2. This tissue is responsible for producing digestive enzymes and an alkaline fluid known as pancreatic juice.
3. The enzymes and juice are secreted into ducts which eventually lead to the pancreatic duct.
4. From here they are released into the duodenum, the top part of the small intestines.
5. The pancreas produces three important types of digestive enzymes: amylases, protesases and lipases

Question 18

Describe the role of the pancreas as an endocrine gland

Answer 18

1. Responsible for producing insulin and glucagon- essential role in controlling blood glucose concentration.
2. Within the exocrine tissue there are small regions of endocrine Islets of Langerhans.
3. The cells of the islets of Langerhans are responsible for producing insulin and glucagon, and secreting these hormones directly into the bloodstream

Question 19

Draw a diagram of a pancreas section, label it and annotate with the functions of the structures labelled.

Answer 19

1. Islets of langerhans-
   a) lightly stained
   b) large and sperical clusters
   c) endocrine pancreas
   d) produce and secrete hormones
2. Pancreatic acini
   a) darker stained
   b) small, berry-like clusters
   c) exocrine pancreas
   d) produce and secrete digestive enzymes

Question 20

Identify the components of the pancreas in a photomicrograph of a stained section.

Answer 20

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1. Dark pink surroundings is the pancreatic acini
2. Light pink big circle in the middle of pancreatic acini is the islet of Langerhan

Question 21

Define α-cell

Answer 21

1. Present in the islet of Langerhan
2. They produce and secrete glucagon
3. stained pink

Question 22

Define β-cell

Answer 22

1. Present in the islet of Langerhan
2. They produce and secrete insulin
3. stained blue

Question 23

Define Islet of Langerhans

Answer 23

Specialised cells within the pancreas responsible for producing insulin and glucagon

Question 24

Define acinus

Answer 24

A small sac-like cavity in a gland, surrounded by secretory cells

Question 25

Define tubule/central duct/pancreatic duct

Answer 25

1. Exit way for enzymes produced by the acini into the small intestine 2. A tube leading from the pancreas to the duodenum

Question 26

Define insulin

Answer 26

1. A globular protein hormone involved in the regulation of blood glucose concentration

Question 27

Define glucagon

Answer 27

1. A hormone formed in the pancreas which promotes the breakdown of glycogen to glucose in the liver.

Question 28

Describe and explain how the ultrastructure of the α- and β-cells in the islets of Langerhans is specialised to manufacture and secrete hormones.

Answer 28

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Question 29

State the “normal” blood glucose concentration.

Answer 29

90mg cm-3

Question 30

Name the two hormones involved in regulating blood glucose concentration

Answer 30

1. Insulin | 2. Glucagon

Question 31

State the condition in which insulin is released and from which cells, and describe how insulin has its effect on cells.

Answer 31

1. Produce by the β-cells of the islets of Langerhans in the pancreas 2. If blood glucose concentration is too high β-cell detect this rise in blood glucose concentration and respond by secreting insulin directly into the blood stream 3. Virtually all body cells have insulin receptors on their cell surface membrane (except rbc) 4. When insulin binds to its glycoprotein receptor, it causes a change in the tertiary structure of the glucose transport protein channels. 5. This causes the channels to open allowing more glucose to enter the cell. 6. Insulin also activates enzymes within some cells to convert glucose to glycogen and fat

Question 32

State the effects insulin has on cells.

Answer 32

Lowers blood glucose concentration by: 1. Increasing the rate of absorption of glucose by cells, in particular skeletal muscle cells 2. Increasing the respiratory rate of cells- this increases their need for glucose and causes a higher uptake of glucose from the blood 3. Increasing the rate of glycogenesis- insulin stimulates the liver to remove glucose from the blood by turning the glucose into glycogen and storing it in the liver and muscle cells 4. Increasing the rate of glucose to fat conversion 5. Inhibiting the release of glucagon from the α-cells of the islets of Langerhans

Question 33

Define glycogenesis

Answer 33

1. Production of glycogen from glucose- decreases blood-sugar concentration

Question 34

Define glycogenolysis

Answer 34

1. Process in which glycogen stored in the liver and muscle cells is broken down into glucose which is released into the bloodstream

Question 35

Define gluconeogenesis

Answer 35

1. Production of glucose from non-carbohydrate sources which is released into the blood stream

Question 36

Describe 3 other factors that affect blood glucose concentration.

Answer 36

1. Respiration- some of the glucose in blood is used by cells to release energy. This is required to perform normal body functions. 2. Diet- When you eat carbohydrate-rich foods such as pasta and rice etc, the carbohydrates the contain are broken down in the digestive system to release glucose 3. Stress- increases blood-sugar levels

Question 37

Explain why insulin must be constantly secreted in order to maintain its effect

Answer 37

1. Insulin is broken down by enzymes in the cells of the liver. 2. Therefore to maintain its effect it has to be constantly secreted

Question 38

Explain why it is important that insulin is constantly being broken down by enzymes

Answer 38

1. As your blood-glucose concentration returns to the normal, you do not want to maintain a higher level of glycogenesis 2. So it needs to be constantly broken down to ensure you don't have too low a blood-glucose concentration

Question 39

State the condition in which glucagon is released and from which cells, and describe how glucagon has its effect on cells.

Answer 39

1. Produced by the α-cells of the islets of Langerhans in the pancreas 2. If blood glucose concentration is too the low, the α-cells detect this fall in blood glucose concentration and respond by secreting glucagon directly into the bloodstream 3. Only cells in the body which have glucagon receptors are the liver cells and fat cells - theses are the only cells that can respond 4. As blood-glucose returns to normal, this is detected by α-cells, when it rises above a set level, the α-cells reduce their secretion of glucagon- negative feedback

Question 40

State the effect glucagon has on cells.

Answer 40

1. Glycogenolysis- the liver breaks down its glycogen store into glucose and releases it backs into bloodstream 2. Reducing the amount of glucose absorbed by the liver cells 3. Increasing gluconeogenesis- increasing the conversion of amino acids and glycerol into glucose in the liver

Question 41

Draw a flow chart showing the negative feedback system that controls blood sugar level.

Answer 41

1. Insulin and glucagon are antagonistic hormones, that is, they work against each other 2. The system of maintaining blood glucose concentration is said to be self-regulating, as it is the level of glucose in the blood that determines the quantity of insulin and glucagon that is released. 3. Blood glucose concentration is not constant, but fluctuates around a set point as the result of negative feedback. 4. In times of stress adrenaline is released by the body, which raises the blood glucose concentration to allow more respiration to occur

Question 42

Describe how insulin is secreted by beta cells in response to a high blood glucose concentration.

Answer 42

1. At normal blood glucose concentration levels, potassium channels in the plasma membrane of β cells are open and potassium ions diffuses out of the cell. 2. When blood glucose concentration rises, glucose enters the cell by a glucose transporter. 3. The glucose is metabolised inside the mitochondria, resulting in the production of ATP 4. The ATP binds to potassium channels and causes them to close. They are known as ATP-sensitive potassium channel. 5. As potassium ions can no longer diffuse out of the cell, the potential difference reduces and depolarisation occurs. 6. Depolarisation causes the voltage-gated calcium channels to open 7. Calcium ions enter the cell and cause secretory vesicles to release the insulin they contain by exocytosis

Question 43

Define diabetes mellitus

Answer 43

1. Medical condition which affects a person's ability to control their blood-glucose concentration

Question 44

Define Type 1 diabetes

Answer 44

1. Patients with type 1 diabetes are unable to produce insulin. 2. The β-cells in the islets of Langerhans do not produce insulin. 3. The cause of type 1 diabetes is not known, so at the moment, the disease cannot be prevented or cured, but it is possible to treat the symptoms 4. Evidence suggests that it arises as a result of an autoimmune response where the body's own immune system attacks the β-cells.

Question 45

Define type 2 diabetes

Answer 45

1. Patients with type 2 diabetes cannot effectively use insulin and control their blood-sugar levels. 2. This is either because the person's β cells do not produce enough insulin or the person's body cells do not respond properly to insulin 3. This is often because the glycoprotein insulin receptor on the cell membrane does not work properly 4. The cells lose their responsiveness to insulin and therefore do not take up enough glucose leaving it in the bloodstream.

Question 46

Define hyperglycaemia

Answer 46

An excess of glucose in the bloodstream, it is a common effect of uncontrolled diabetes.

Question 47

Define hypoglycaemia

Answer 47

Deficiency of glucose in the bloodstream

Question 48

How is type 1 diabetes treated

Answer 48

1. Type 1 diabetes is controlled by regular injections of insulin and is therefore said to be insulin dependent 2. People regularly test their blood glucose concentration. 3. Based on the concentration the person can work out the dose of insulin they need to inject. 4. The insulin administered increases the amount of glucose absorbed by cells and causes glycogenesis to occur resulting in a reduction of blood glucose concentration. 5. Too little or too much results in hyper/hypoglycaemia

Question 49

How is type 2 diabetes treated

Answer 49

1. Regulate persons carbohydrate intake through their diet and matching this to their exercise 2. Some cases this is not enough so drugs also have to be used. 3. These drugs can be ones that stimulate insulin production, drugs that slow down the rate at which the body absorbs glucose from the intestine and ultimately even insulin injections

Question 50

List 4 benefits of using insulin produced from genetically engineered bacteria rather than from pigs to treat diabetes. For each benefit explain why the benefit exists.

Answer 50

1. Human insulin is produced in a pure form- means it is less likely to cause allergic reactions 2. Insulin can be produced in much higher quantities 3. Production costs are must cheaper 4. People's concern over using animal products in humans, which may be religious or ethical, are overcome

Question 51

Describe how stem cells could be used to treat diabetes

Answer 51

1. Diabetes researchers have been searching for ways to replace the faulty β cells in the pancreatic islets of diabetic sufferers 2. As type 1 diabetes results from the loss of a single cell type and there is evidence that a relatively small number of islet cells can restore the insulin production, 3. It is likely that the stem cells used in diabetes would be taken from embryos. 4. Totipotent stem cells have the potential stem cells have the potential to grow into any body's cell types.

Question 52

Describe the potential benefits of stem cell treatment for Type 1 diabetes over insulin injection or whole pancreas transplantation.

Answer 52

1. Donor availability would not be an issue- stem cells could produce an unlimited source of new β cells 2. Reduced likelihood of rejection problems as embryonic stem cells are generally not rejected by the body. Stem cells can also e made by somatic cell nuclear transfer. 3. People no longer have to inject themselves with insulin

Question 53

Describe one risk of using stem cells to treat Type 1 diabetes.

Answer 53

1. Slight risk of rejection 2. Risk that stem cells transplanted into the body might induce the formation of tumours as a result of unlimited cell growth.

Question 54

Explain why stem cell treatment is not likely to be suitable for treating Type 2 diabetes.

Answer 54

1. All body cells faulty in type 2, not possible to replace all. 2. In type 1 it is only one type of cell so it may be possible to replace that cell type using stem cells that are programmed to differentiate into the β cells in the pancreas.