5.1 Communication And Homeostasis

Question 1

What is the definition of homeostasis?

Answer 1

Act of keeping conditions internally stable

Question 2

What do good communication systems consist of?

Answer 2

-1. Covers whole body
2. Allows cells to communicate
3. Allows specific communication
4. Allows rapid communication
5. Enables short and long term responses

Question 3

What is the definition of negative feedback?

Answer 3

Change to internal environment is detected so change is signalled to cells and a response occurs

Question 4

What is the definition of positive feedback?

Answer 4

Increases the original change which destabilises the system
E.g. while in labour

Question 5

What are ectotherms?

Answer 5

Animals that use their surroundings to warm their bodies so their core temperature is dependent on their environment

Question 6

What are the advantages of being ectothermic?

Answer 6

• Less energy required
• Less food in respiration
• Can survive longer without food

Question 7

What are the disadvantages of being ectothermic?

Answer 7

• Not sustainable in cold conditions
• Not capable of activity in winter months
• Metabolic reactions are slower

Question 8

What point must you include in a question about temperature regulation of ectotherms?

Answer 8

Mention surface area/radiation

Question 9

What is the definition of an endotherm?

Answer 9

Animals that rely on metabolic processes to warm their bodies and maintain their core temperature

Question 10

What are the advantages of being endothermic?

Answer 10

• Body temperature is easier to maintain and constant in cooler environments
• Capable of activity throughout the year
• Can inhabit colder parts of the planet

Question 11

What are the disadvantages of being endothermic?

Answer 11

• More energy to maintain
• Need to eat more
• Less energy used in growth

Question 12

What part of the brain detects changes in body temperature?

Answer 12

Thermoregulatory centre in Hypothalamus

Question 13

What are peripheral temperature receptors?

Answer 13

Skin receptors monitor changes in skin temperature
‘Early warning system’

Question 14

What happens in vasoconstriction?

Answer 14

Arteriole is constricted and less blood to surface
Sphincter is contracted
Shunt vessels in use

Question 15

What happens in vasodilation?

Answer 15

Arteriole is relaxed and dilated,sphincter is relaxed so shunt vessel is relaxed as well

Question 16

What is the definition of a exocrine gland?

Answer 16

Do not release hormones into blood but instead via ducts

Question 17

What is the definition of an endocrine gland?

Answer 17

Ductless glands so hormones are released into blood

Question 18

What are protein hormones?

Answer 18

Insoluble hormones which do not enter cell

Question 19

How do protein hormones trigger a response?

Answer 19

1. Hormone binds to complimentary receptor on cell surface plasma membrane
2. This triggers a protein which activates an enzyme
3. ATP becomes cAMP due to enzyme (secondary messenger)
4. cAMP activates another enzyme forming enzyme

Question 20

What are steroid hormones?

Answer 20

Lipid soluble hormones made from cholesterol

Question 21

How does a steroid hormone bring about a response?

Answer 21

1. Hormone passes through plasma membrane
2. Hormone binds to complimentary shaped receptor in cytoplasm then passes through nuclear pore in nucleus
   - Hormone receptor complex binds with DNA which transcribes corresponding mRNA
3. MRNA passes through the ribosome
4. Protein is synthesised

Question 22

Where is adrenaline and noradrenaline synthesised?

Answer 22

In the medulla

Question 23

What does adrenaline do?

Answer 23

Increases heart rate
Increases blood pressure
Increases blood flow to muscles and brain
Glycogenolysis is increased

Question 24

What is noradrenaline and what does it do?

Answer 24

Protein hormone
Increases heart rate
Increases ventilation by widening air ways
Narrowing blood vessels in digestive system

Question 25

What is the function of mineralocorticoids?

Answer 25

Steroid hormone Helps control blood pressure by maintaining correct minerals Acts on kidneys for selective reabsorption

Question 26

What are the role of the glucocorticoids?

Answer 26

Cortisol- Regulates metabolism Corticosterone- regulates immune system and inflammatory response

Question 27

How is the pancreas both endocrine and exocrine?

Answer 27

Has ducts to release digestive juices but releases insulin into the blood

Question 28

What tissue in the pancreas is exocrine tissue?

Answer 28

Pancreatic acini

Question 29

What tissue in the pancreas is endocrine?

Answer 29

Islets of langerhans

Question 30

What is the difference between alpha and beta cells in the pancreas?

Answer 30

Alpha cells- secrete glucagon Beta cells- Secrete insulin

Question 31

Why is it essential to have the correct blood glucose level?

Answer 31

If blood glucose is too low cells will restore less meaning less energy and if blood glucose is too high osmosis will cause blood cells to shrivel and less oxygen can be carried

Question 32

What are the sources of blood glucose?

Answer 32

- Food - Gluconeogenesis (amino acids and fats being metabolised) - Glycogen being broken down

Question 33

What is the response if blood glucose is too high?

Answer 33

1. Detected by beta cells in islets of langerhans 2. Beta cells secrete insulin 3. Insulin attaches to insulin receptors on some cells causing protein channels to open to glucose 4. Insulin activates enzyme which converts glucose to glycogen 5. Enzymes in liver break down excessive insulin

Question 34

How is insulin secreted?

Answer 34

1. High conc blood glucose outside of cell 2. Glucose entering cell through glucose transporter 3. Mitochondria do higher rate of respiration produce more ATP 4. K+ channel closes 5. Membrane depolarised 6. Ca2+ channel opens and calcium diffuses into cell 7. Ca2+ helps form secretory vesicles which then exit containing insulin

Question 35

What is the cause of type 1 diabetes?

Answer 35

Beta cells in islets of langerhans do not produce insulin

Question 36

What causes type 2 diabetes?

Answer 36

Either beta cells do not produce enough insulin or body cells no longer respond to insulin

Question 37

What is the cause of type 2 diabetes?

Answer 37

Excess body wight,physical inactivity and habitual overeating

Question 38

How can type 1 diabetes be managed?

Answer 38

- Regular insulin injections - Regular blood glucose readings

Question 39

How can type 2 diabetes be managed?

Answer 39

- Regulate carbohydrate intake - Increase exercise level - Insulin stimulating drugs

Question 40

What are the advantages and disadvantages of medically produced insulin?

Answer 40

Less allergic reactions as is pure insulin Produced fast enough to meet demand Cheaper Less concerns over ethics Not a permanent solution,have to permanently inject

Question 41

What are the advantages and disadvantages in stem cell treatment for diabetes?

Answer 41

Positives: Donor availability is not an issue Reduced likelihood of rejection Permanent solution Negative May induce unnatural growth Immune responses may occur Need a lot of beta cells to be equivalent of a pancreas