Communications and Homeostasis

Question 1

Signalling between adjacent and distant cells

Answer 1

Signal molecule attached to csm

Requires signal molecule to be able to move between cells

Question 2

Hydrophilic + hydrophobic signal molecule

Answer 2

Hydrophilic = need cell surface receptor

Hydrophobic = pass through plasma membrane
To intracellular receptor

Question 3

Positive feedback
Example

Answer 3

Change away from optimum
Leads to increase in original change
Amplifies change

Stimulus = small influx of Na+ into neurones
Results in Na channels to open
= more Na+ enter

Question 4

Negative feedback

Answer 4

Change away from optimum causing a return to original value

Question 5

Difference between ectotherm + endotherm

Answer 5

Endotherms can regulate their own body temp
Independent of external sources