I am required to ” write an essay in which you describe examples of descending

I am required to ” write an essay in which you describe examples of descending control in the senses of pain, hearing and proprioception, explaining how these descending pathways influence sensory input to the brain. ”
The essay must not be more than 1100 words or there will be a penalty of 10%. The essay needs to be very specific and concise. 
All information required for the essay should only be from the module materials ONLY. 
References example: Robinson, D., Greville-Harris, M., Roberts, D., Parvin, E., Meek, K., Bowmaker, J., Westland, S., Derrington, A. and Hurlbert, A. (2015) “Block 5 Vision: From the retina to the cortex”, SD329 Book 3: Vision and the Chemical Senses, Milton Keynes, The Open University, p.113.
All refefences need to be labelled a, b ,c and so on.