Dermatomes overlap substantially, so that injury to a spinal nerve does not lead to the complete loss of sensation in the relevant skin region. 

Muscle spindles are composed of intrafusal fibers called nuclear bag fibers and nuclear chain fibers. What is the difference between these fiber types, what type of information do they provide, and what type of sensory afferents innervate each of the different fibers?

Which of these afferent fibers have the fastest conduction velocity? Which ones are the slowest? Explain WHY?

In the dark calcium ions flow into photoreceptor cells.   How does calcium lead to a decrease in dark current and prevent the cell from depolarizing too much? What is this process called?

For distant objects, the lens has a shape, and this shape is produced by a of the ciliary muscles.

EXTRA CREDIT 🙂 3. Which type of photoreceptor would produce the following type of current?  How do you know?  It says inward current – what type of ions might be responsible for this current? Why? (2 pts)   

When viewed with an ophthalmoscope, there are several different structures that can be observed on the surface of the retina, including the optic disk and macula lutea.  How would you identify these two structures on an image of the retina and what functions and characteristics would you use to describe these regions? 

Compare the cutaneous mechanosensory and discriminative pain pathways from the lower body with respect to anatomy and sensory modality. For each pathway, where are the cell bodies and axon terminals of the first-, second-, and third-order neurons? Where does each pathway decussate?  Be as detailed as possible! (8 pts) 

The touch sensitivity of a given area can be measured by the two-point discrimination protocol.  Larger receptive field areas will have a innervation density and would produce a  two-point discrimination.

Match the function with the appropriate structure of the eye (each will only be used once):