Need help on Bio SAC.

[crayolé]

It's open book so we can pretty much write out the whole thing beforehand.

Its only on thermoregulation so any other form of homeostasis isnt needed

What sorts of things should I include to get the full marks?
Is there a website where I could find this sort of information?

Thanks!

[seth_129]

Firstly you need to make sure that you are able to draw a stimulus response diagram for thermoregulation and be able to explain how this model is an example of negative feedback. It is possible that you will need to draw two of these diagrams as the whale will need to lose heat in the equatorial waters and prevent heat lose in the Antarctic waters.

Of course this means that you need to show how negative feedback ties in with the three dot points you are asked to discuss.

Structural Variations: - Whales have a layer of blubber between their skin and muscle that insulates them from the outside environment.

Homeostatic Mechanism: - This is where you outline how negative feedback would assist thermoregulation. You would need to be able to describe how a message is received, transferred and effected. This means that you should discuss the use of a thermoreceptor to detect the change which is then sent to the CNS via a sensory neuron. At this point I would meantion how action potentials are used to send the message along a neuron and then neurotransmitters are used to communicate between neurons. Once the message reaches the CNS the message is then relayed to a motor neuron which takes the message to a muscle (eg muscles in the wall of an artery to constrict the artery to prevent heat loss) to enact a response.

Physiological Changes: - They use countercurrent flow to keep their internal temperature constant. Countercurrent flow involves blood travelling in the arteries towards the extremities, which in the case of a cold environment warms the blood returning to the body in the adjacent veins. The outgoing blood to the extremities is cooled in the process but not enough to affect cell activities. Because the gradient of temperature difference between the foot and the surroundings is reduced, less heat is lost (Please see diagram below). They are also able to alter the flow of blood to their extemities using vascoconstriction and vascodilation.

Artery  --------> (Blood Flow)
30^oC           25^oC          20^oC          15^oC          10^oC          5^oC
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
29^oC           24^oC          19^oC          14^oC          9^oC            4^oC
Vein <----------

Hope this helps