How sensations climb from the spinal cord to the cortex along chains of three neurons, which of them travel in the dorsal column pathway and which in the anterolateral system, and what goes wrong when these pathways are damaged. Examiners ask most for the two pathways, traced with a labelled diagram, and for dissociated anesthesia.
Topics, in the book’s order
- Ascending tracts: dorsal column and anterolateral system · pp. 1007–1010 · asked 7 times
- Pathways for specific sensations · pp. 1010–1011 · asked once
- Abnormalities of dorsal column sensations · pp. 1011–1012
When you’ve read them: Quiz 119 · Ascending Pathways, 15 questions.
After this chapter you should be able to
- describe how the neurons of an ascending pathway are arranged, from first order to third
- list the sensations carried in the dorsal column pathway and in the anterolateral system
- draw and label the dorsal column pathway and the anterolateral system
- explain how the main ascending pathways work
- define the common abnormalities of sensation and give their causes
Going further: the connections and functions of the ascending pathways and of the dorsal column nuclei, the physiology of each sensation, and the physiological basis of each abnormality of dorsal column sensation.
Viva checklist
- The first-, second- and third-order neurons of a sensory pathway, and which of them crosses
- The six sensations of the dorsal column pathway
- The two tracts of the anterolateral system and what each carries
- Gracile versus cuneate fasciculus: position and territory
- Where the dorsal column pathway crosses, and where the spinothalamic tracts cross
- The cluster and non-cluster regions of the dorsal column nuclei
- The thalamic nuclei each pathway relays in
- Why a lesion in one half of the cord takes touch on one side and pain on the other
- The touch receptors, rapidly versus slowly adapting
- Two-point discrimination on the fingertip and on the back
- The cortical sensations, and why stereognosis fails early in cortical disease
- Anesthesia, hyperesthesia, alloesthesia, paresthesia, agraphesthesia: definitions and causes
- Dissociated anesthesia: its causes and its basis
- The Romberg sign and what it tests