Question

Compare and contrast the Dorsal Column-Medial Lemniscal System and the Anterolateral System (in terms of both FUNCTION and ANATOMICAL distribution).

Answer 1

Comparison based on structure/anatomy:

	PCML Pathway	AL Pathway
SENSORY PATHWAY SOURCE	Skin and Joints	Skin
PATHWAY DECUSSATION AT THE LEVEL OF	Brain (Sensory decussation)	Spinal cord
PARTS BASED ON FUNCTIONS	No parts	Lateral spinothalamic tract, anterior spinothalamic tract
SECONDARY NEURONS	Absent	Present. They are called tract cells

Both pathways end at postcentral gyrus in the cerebral cortex. Both have three neurons to convey sensory signals.

Comparison based of functions:

	PCML Pathway	AL Pathway
AFFECTIVE SENSATION	Absent	Present, sensation is accompanied by a compulsion to act
DUAL ACTION	Absent, only sensation to touch	Present, sensation to touch and pressure as well as temperature and pain
AXONS OF SECOND NEURON	Cross over to the otherside of the medulla to form medial lemniscus, Axons from legs become ventral and those from arms and head become lateral here.	Cross at every segment in the spinal cord, thus allowing detection if lesion is in brain or spinal cord