Question on PNS and CNSWatch
Mark scheme answer:
1. receptor detects stimulus (1 mark)
2. sensory neurones conduct action potentials (1 mark) from receptors to CNS (1 mark)
3. motor neurones conduct action potentials (1 mark) from CNS to effector (1 mark)
4. relay neurones conduct action potentials (1 mark) from sensory to motor neurones (1 mark)
5. CNS/brain, coordinates response (1 mark)
My question for this question is
1) Why is the mark scheme answer only about the CNS and not the PNS when the question is asking for both?
I don't understand how PNS is in the Q when it's nowhere in the answer. If it is in the answer, or implied in the answer, can you please explain where and how?
2) Shouldn't the question be 'outline the roles of NEURONES in responding to a change in environment/stimulus'?
How do we know we should add the role of neurones in answer when the question only asks about CNS and PNS?
Thank you so much!!
The PNS is made up of the pairs of nerves that originate from the brain/spinal cord (so the sensory and motor neurones are part of the PNS). So when the mark scheme states "sensory/motor neurones conduct action potentials" (points 2. and 3.), those are referring to the roles of the PNS in response to a stimulus.
Hope this helps