472
UNIT 3
Regulation and Integration of the Body
12
Primary motor cortex
Internal capsule
Cerebral
peduncle
Midbrain
Cerebellum
Cerebrum
Medulla oblongata
Cervical spinal cord
Skeletal
muscle
Pyramids
Decussation
of pyramids
Lateral
corticospinal
tract
Ventral
corticospinal
tract
Lumbar spinal cord
Somatic motor neurons
(lower motor neurons)
Red nucleus
Pons
Rubrospinal tract
(a)
(b)
Pyramidal cells
(upper motor neurons)
Rubrospinal tract
Pyramidal (lateral and ventral corticospinal) pathways
Figure 12.32
Three descending pathways by which the brain influences movement.
Cross sections up to the cerebrum, which is shown in frontal section.
(a)
Pyramidal (lateral and
ventral corticospinal pathways) are direct pathways that control skilled voluntary movements.
(b)
The rubrospinal tract, one of the indirect pathways, helps regulate muscle tone.
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