448
UNIT 3
Regulation and Integration of the Body
12
4.
Ten, via the superior peduncles, the cerebellum dis-
patches to the cerebral motor cortex its “blueprint” for
coordinating movement. Cerebellar fibers also send infor-
mation to brain stem nuclei, which in turn influence mo-
tor neurons of the spinal cord.
Just as an automatic pilot compares a plane’s instrument
readings with the planned course, the cerebellum continually
compares the body’s performance with the higher brain’s inten-
tion and sends out messages to initiate appropriate corrective
measures. Cerebellar injury results in loss of muscle tone and
clumsy, unsure movements.
2.
At the same time, the cerebellum receives information
from proprioceptors throughout the body (regarding ten-
sion in the muscles and tendons, and joint position) and
from visual and equilibrium pathways. Tis information
enables the cerebellum to evaluate body position and
momentum—where the body is and where it is going.
3.
Te cerebellar cortex calculates the best way to coordinate
the force, direction, and extent of muscle contraction to
prevent overshoot, maintain posture, and ensure smooth,
coordinated movements.
Anterior
lobe
Primary
fissure
Posterior
lobe
Vermis
Horizontal
fissure
Vermis
(c)
(d)
(a)
(b)
Medulla
oblongata
Medulla
oblongata
Flocculonodular lobe
Flocculonodular lobe
Choroid
plexus of
fourth
ventricle
Fourth
ventricle
Posterior
lobe
Posterior
lobe
Arbor
vitae
Arbor vitae
Cerebellar cortex
Cerebellar
cortex
Anterior lobe
Anterior lobe
Cerebellar
peduncles
Superior
Middle
Inferior
Choroid plexus
Pons
Figure 12.15
Cerebellum.
(a)
Photo of midsagittal section.
(b)
Drawing of parasagittal
section.
(c)
Photograph of the posterior aspect of the cerebellum.
(d)
Three body maps of the
cerebellar cortex (in the form of homunculi).
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