5.1 Communication And Homeostasis Flashcards
What is the definition of homeostasis?
Act of keeping conditions internally stable
What do good communication systems consist of?
-1. Covers whole body
2. Allows cells to communicate
3. Allows specific communication
4. Allows rapid communication
5. Enables short and long term responses
What is the definition of negative feedback?
Change to internal environment is detected so change is signalled to cells and a response occurs
What is the definition of positive feedback?
Increases the original change which destabilises the system
E.g. while in labour
What are ectotherms?
Animals that use their surroundings to warm their bodies so their core temperature is dependent on their environment
What are the advantages of being ectothermic?
- Less energy required
- Less food in respiration
- Can survive longer without food
What are the disadvantages of being ectothermic?
- Not sustainable in cold conditions
- Not capable of activity in winter months
- Metabolic reactions are slower
What point must you include in a question about temperature regulation of ectotherms?
Mention surface area/radiation
What is the definition of an endotherm?
Animals that rely on metabolic processes to warm their bodies and maintain their core temperature
What are the advantages of being endothermic?
- Body temperature is easier to maintain and constant in cooler environments
- Capable of activity throughout the year
- Can inhabit colder parts of the planet
What are the disadvantages of being endothermic?
- More energy to maintain
- Need to eat more
- Less energy used in growth
What part of the brain detects changes in body temperature?
Thermoregulatory centre in Hypothalamus
What are peripheral temperature receptors?
Skin receptors monitor changes in skin temperature
‘Early warning system’
What happens in vasoconstriction?
Arteriole is constricted and less blood to surface
Sphincter is contracted
Shunt vessels in use
What happens in vasodilation?
Arteriole is relaxed and dilated,sphincter is relaxed so shunt vessel is relaxed as well
What is the definition of a exocrine gland?
Do not release hormones into blood but instead via ducts
What is the definition of an endocrine gland?
Ductless glands so hormones are released into blood
What are protein hormones?
Insoluble hormones which do not enter cell
How do protein hormones trigger a response?
- Hormone binds to complimentary receptor on cell surface plasma membrane
- This triggers a protein which activates an enzyme
- ATP becomes cAMP due to enzyme (secondary messenger)
- cAMP activates another enzyme forming enzyme
What are steroid hormones?
Lipid soluble hormones made from cholesterol
How does a steroid hormone bring about a response?
- Hormone passes through plasma membrane
- 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 - MRNA passes through the ribosome
- Protein is synthesised
Where is adrenaline and noradrenaline synthesised?
In the medulla
What does adrenaline do?
Increases heart rate
Increases blood pressure
Increases blood flow to muscles and brain
Glycogenolysis is increased
What is noradrenaline and what does it do?
Protein hormone
Increases heart rate
Increases ventilation by widening air ways
Narrowing blood vessels in digestive system
What is the function of mineralocorticoids?
Steroid hormone
Helps control blood pressure by maintaining correct minerals
Acts on kidneys for selective reabsorption
What are the role of the glucocorticoids?
Cortisol- Regulates metabolism
Corticosterone- regulates immune system and inflammatory response
How is the pancreas both endocrine and exocrine?
Has ducts to release digestive juices but releases insulin into the blood
What tissue in the pancreas is exocrine tissue?
Pancreatic acini
What tissue in the pancreas is endocrine?
Islets of langerhans
What is the difference between alpha and beta cells in the pancreas?
Alpha cells- secrete glucagon
Beta cells- Secrete insulin
Why is it essential to have the correct blood glucose level?
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
What are the sources of blood glucose?
- Food
- Gluconeogenesis (amino acids and fats being metabolised)
- Glycogen being broken down
What is the response if blood glucose is too high?
- Detected by beta cells in islets of langerhans
- Beta cells secrete insulin
- Insulin attaches to insulin receptors on some cells causing protein channels to open to glucose
- Insulin activates enzyme which converts glucose to glycogen
- Enzymes in liver break down excessive insulin
How is insulin secreted?
- High conc blood glucose outside of cell
- Glucose entering cell through glucose transporter
- Mitochondria do higher rate of respiration produce more ATP
- K+ channel closes
- Membrane depolarised
- Ca2+ channel opens and calcium diffuses into cell
- Ca2+ helps form secretory vesicles which then exit containing insulin
What is the cause of type 1 diabetes?
Beta cells in islets of langerhans do not produce insulin
What causes type 2 diabetes?
Either beta cells do not produce enough insulin or body cells no longer respond to insulin
What is the cause of type 2 diabetes?
Excess body wight,physical inactivity and habitual overeating
How can type 1 diabetes be managed?
- Regular insulin injections
- Regular blood glucose readings
How can type 2 diabetes be managed?
- Regulate carbohydrate intake
- Increase exercise level
- Insulin stimulating drugs
What are the advantages and disadvantages of medically produced insulin?
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
What are the advantages and disadvantages in stem cell treatment for diabetes?
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
