470
UNIT 3
Regulation and Integration of the Body
12
Axons of first-order
neurons
Temperature
receptors
Lateral
spinothalamic
tract
(axons of
second-order
neurons)
Pain receptors
Primary
somatosensory
cortex
Axons of third-order
neurons
Thalamus
Cerebrum
Midbrain
Spinocerebellar pathway
Spinothalamic pathway
Cerebellum
Pons
Medulla oblongata
Fasciculus cuneatus
(axon of first-order sensory neuron)
Fasciculus gracilis
(axon of first-order sensory neuron)
Axon of
first-order
neuron
Muscle spindle
(proprioceptor)
Joint stretch
receptor
(proprioceptor)
Cervical spinal cord
Touch
receptor
Medial lemniscus (tract)
(axons of second-order neurons)
Dorsal
spinocerebellar
tract
(axons of
second-order
neurons)
Nucleus gracilis
Nucleus cuneatus
Lumbar spinal cord
(a)
(b)
Dorsal column–medial lemniscal pathway
Figure 12.31
Pathways of selected
ascending spinal cord tracts.
Cross sections
up to the cerebrum, which is shown in frontal
section.
(a)
The spinocerebellar pathway (left)
transmits proprioceptive information only to
the cerebellum, and so is subconscious. The
dorsal column–medial lemniscal pathway
transmits discriminative touch and conscious
proprioception signals to the cerebral cortex.
(b)
The lateral spinothalamic pathway
transmits pain and temperature.
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