Module 5 Hormonal communication essential note

Question 1

Describe the key features of endocrine communication

Answer 1

1. Chemical messengers called hormones are produced by the cells of endocrine glands
2. These are secreted into tissue fluid and diffuse into blood
3. The hormone is transported throughout the body in the blood circulation
4. Hormones diffuse out of the blood to all organs
5. Target cells/organs detect the hormone, which causes the cells to respond

Question 2

Describe how endocrine organs c an be stimulated

Answer 2

1. By effector neurones of the nervous system
2. By other hormones (from other endocrine glands)
3. Direct detection of a stimulus (eg chemicals)

Question 3

Explain why only some organs may respond to a hormone

Answer 3

1. Hormones are detected by cells when they bind to
2. complementary receptor proteins
3. Because cells/organs are differentiated, they can have different receptor proteins
4. Therefore, only specific cells/organs that have the complementary receptor are able to respond to a particular hormone
5. These are called target cells/organs

Question 4

State how target cells generally respond to a hormone signal

Answer 4

1. The hormone binds to a complementary receptor protein on the cell
2. This results in intracellular signalling events
3. The nucleus may transcribe new genes (new proteins produced)
4. Some proteins in the cell may be activated
5. New proteins, or newly activated proteins change the behaviour of the cell
6. This results in a response to the hormonal signal

Question 5

Describe the types and properties of hormones

Answer 5

1. There are two types of hormone, peptide hormones and steroid hormones
2. Peptide hormones are composed of amino acids
3. Peptide hormones are hydrophilic and water-soluble
4. Steroid hormones are lipid (cholesterol-like) molecules
5. Steroid hormones are hydrophobic and transported by plasma proteins

Question 6

Describe how steroid hormones induce responses in target cells

Answer 6

1. Steroid hormones are lipid soluble
2. They can diffuse through the cell membrane
3. They bind to a complementary cytoplasmic receptor protein
4. This complex enters the nucleus and acts as a transcription factor
5. Activating the expression of specific genes, and causing the synthesis of specific proteins
6. This will change the function of the cell

Question 7

Describe how peptide hormones induce responses in target cells

Answer 7

1. The peptide hormone is hydrophilic and cannot enter cells It binds to a complementary receptor on the cell surface membrane
2. This causes the production of a second messenger
3. chemical inside the cell (eg cyclic AMP)
4. The second messenger binds to and activates enzymes in the cytoplasm
5. This is associated with changes in the function and behaviour of the cell

Question 8

State the differences between neuronal and hormonal communication

Answer 8

1. The endocrine system uses hormones to communicate, the nervous system uses nerve impulses
2. Transport of the signal occurs via the circulatory system in the endocrine system, but the neurones in the nervous system
3. Communication via hormones is slower than nerve impulse
4. The effects of endocrine signalling can be longer-lasting than those of the nervous system
5. Hormones travel to all parts of the body, but the nervous system has specific connections
6. Hormones can have a wider range of effectors/targets

Question 9

Describe the structure of the adrenal glands

Answer 9

1. The adrenal glands are located at the top of each kidney
2. They have two main functional areas
3. The lighter outer region is the adrenal cortex
4. The darker central region is the adrenal medulla

Question 10

State the types of hormone produced t he adrenal cortex and t heir functions

Answer 10

Question 11

State the types of hormone produced t he adrenal medulla and their functions

Answer 11

Question 12

Describe the histology of the pancreas

Answer 12

1. Pancreatic acinar cells secrete digestive enzymes into spaces that converge to form the pancreatic duct that leads to the digestive system (exocrine function)
2. Islets of Langerhans can be seen as lighter staining
3. but alpha and beta cells cannot be visually discriminated with standard staining
4. Islets contain specialized alpha and beta cells that secrete hormones (endocrine function)
5. Special differential stains show there are m ore beta cells than alpha cells
6. Beta cells secrete insulin
7. Alpha cells secrete glucagon

Question 13

Summarise how glucose homeostasis is carried using negative feedback

Answer 13

1. Blood glucose levels are detected by the pancreatic alpha and beta cells when blood glucose levels rise above the setpoint norm beta cells release insulin
2. insulin causes effectors to decrease blood glucose levels
3. when blood glucose levels fall alpha cells release glucagon
4. glucagon causes effectors to increase in blood glucose levels

Question 14

Explain how high blood glucose levels cause insulin secretion

Answer 14

1. increased blood glucose results in more diffusion of glucose into beta cells the rate of respiration increases, and increases the ATP:ADP ratio
2. this causes surface potassium channels to close
3. positive ions build up inside the cell, causing depolarisation
4. voltage-gated calcium channels open
5. Calcium ions cause exocytosis of insulin-containing vesicles

Question 15

Describe how the effects of insulin on target tissues lowers blood glucose

Answer 15

1. The main targets of insulin are the liver and muscle Increase glucose uptake by facilitated diffusion (especially skeletal muscle)
2. Increased rate of glycogenesis (condensation of glucose
3. into glycogen), liver and muscle cells
4. Increasing rate of glucose to fat conversion
5. Inhibiting the release of glucagon from the pancreatic alpha cells

Question 16

Describe how the effects of glucagon on target tissues increases blood glucose levels

Answer 16

1. The main target of glucagon is the liver
2. Increase glycogenolysis
3. Reducing glucose transport into cells
4. Increase gluconeogenesis (converting amino acids into glucose)
5. Reduced respiration

Question 17

Describe type 1 diabetes

Answer 17

1. Beta cells stop producing insulin
2. Or loss of beta cells due to autoimmunity
3. normally develops in childhood (genetic predisposition)
4. Untreated, the blood glucose concentration is too high
5. Resulting in damage to nerves and blood vessels

Question 18

Describe type 2 diabetes

Answer 18

1. Reduced insulin production
2. Or reduced responsiveness in target tissues (muscles, fat tissue, liver)
3. Causes blood glucose levels to be too high
4. degenerative / environmental nature, for example, over-eating

Question 19

List the symptoms of diabetes

Answer 19

1. high blood glucose concentration
2. glucose present in urine
3. excessive need to urinate (polyuria)
4. Excessive thirst (polydipsia)
5. constant hunger
6. weight loss
7. tiredness
8. blurred vision

Question 20

Describe how type 1 diabetes can be treated

Answer 20

1. treated with insulin injections directly into the blood
2. blood glucose levels must be measured first
3. to determine the dose of insulin required
4. the insulin causes blood glucose levels to drop to the response by target cells, eg, glycogenesis

Question 21

Describe how type 2 diabetes can be treated

Answer 21

1. the symptoms of type 2 diabetes can be milder so initially can be treated by managing diet (regulated carbohydrate intake) and regular exercise (use up blood glucose)
2. if the condition is more serious, drugs can be used:
3. drugs that stimulate insulin production
4. drugs that slow down glucose absorption after digestion
5. eventually insulin injections may be required

Question 22

Describe the disadvantages of using insulin from animals to treat humans

Answer 22

1. insulin can be isolated from the pancreas of animals and used to treat diabetics however, the primary structure is slightly different in different species
2. it can cause allergic reactions
3. quantity extracted is limited
4. It is expensive
5. people can have ethical and religious objections

Question 23

Summarise how insulin can be medically produced, and

state its advantages

Answer 23

1. gene sequencing technology allowed the human gene for insulin to be identified the gene could inserted into plasmids and added to bacterial cells these recombinant bacteria could be grown on large scale in fermenters
2. the human insulin the produced could be purified
3. avoiding allergic reaction and ethical or religious objection

Question 24

State the issues relating to use of pancreatic transplants to treat diabetes

Answer 24

1. Pancreatic transplants are very successful in restoring glucose homeostasis to normal in some cases the islets of Langerhans alone can be transplanted
2. But availability of donors is much lower than demand
3. There is also the risk of rejection
4. And immunosuppressant drugs can cause an increased chance of infection

Question 25

Describe how stem cells can be used to treat diabetes

Answer 25

1. totipotent cells can differentiate into any body cell Given the right chemical stimulus and signals donor stem cells can be directed in vitro to differentiate into pancreatic beta cells
2. which can then be transplanted into the recipient
3. restoring their ability to produce insulin

Question 26

Describe the ethical issues relating to the use of stem cells to treat diabetes

Answer 26

1. totipotent cells can only be derived from developing embryos obtaining totipotent cells means loss of potential human life however, many embryos do get discarded in in vitro fertilisation procedures or pregnancy terminations a few cells can be used to treat many, due to their unlimited replicative potential
2. there is still an issue of tissue rejection
3. transplanted stem cells may be tumorigenic