How sensory signals get from the skin into the spinal cord: the fiber types in a peripheral nerve and what damages them, the dorsal root and its dermatomes, and where each afferent ends in the cord’s laminae. Your book expects no long or short questions here, yet the Bell–Magendie law has been set as a short answer, fiber types turn up in MCQs, and the laminae are a viva favourite.
Topics, in the book’s order
- Afferent fibers, dorsal root and spinal laminae · pp. 1002–1005 · asked 3 times
When you’ve read them: Quiz 118 · Sensory Communication to Spinal Cord, 14 questions.
After this chapter you should be able to
- name the afferent fibers in a peripheral nerve and say what each carries
- explain how axotomy, demyelination, ischemia and compression affect a nerve
- describe how afferent and efferent neurons are arranged in the spinal cord
- explain why the spinal cord laminae matter
Viva checklist
- The Bell–Magendie law, and its exception
- The fiber types in a skin nerve and what each carries
- Where a sensory neuron’s cell body lies, and where its two axons go
- What a dermatome is, and how it helps localize a lesion
- What happens to a neuron after axotomy, on each side of the cut
- Which sensation survives ischemia or compression, and why
- Why a local anesthetic removes pain before touch
- Irritation versus damage of a compressed dorsal root
- The possible destinations of a primary afferent inside the cord
- The Rexed laminae: which are sensory, which motor, and which one is the substantia gelatinosa
- What laminae I, II and III–VI receive and respond to
- Why descending tracts end on the sensory laminae