As the spinal cord enters the skull, it enlarges into the bottommost structure
of the brain, the medulla (or medulla oblongata). The medulla controls
many of the most basic physiological functions for survival, particularly
breathing and the beating of the heart. Reflexes such as vomiting, coughing,
sneezing, and salivating are also controlled by the medulla. The medulla
is sensitive to opiate and amphetamine drugs, and overdoses of these
drugs can impair its normal functioning. Severe impairment can lead to a
fatal shutdown of the respiratory and cardiovascular systems.
Just above the medulla lie the pons, parts of the reticular formation, the
raphe system, and the locus coeruleus. All these structures play a role in
arousal and sleep. The pons plays a major role in initiating rapid eye move
ment (REM) sleep. REM sleep is characterized by repeated horizontal eye
movements, increased brain activity, and frequent dreaming. The reticular
system (sometimes called the reticular activating system, or RAS) stretches
from the pons through the midbrain to projections into the cerebral cortex.
Activation of the reticular system, by sensory stimulation or thinking, causes
increases in arousal and alertness in diverse areas of the brain. For the brain
to pay attention to something, there must be activation from the reticular
formation. The raphe system, like the reticular system, can increase the
brain’s readiness to respond to stimuli. However, unlike the reticular formation,
the raphe system can decrease alertness to stimulation, decrease sensitivity
to pain, and initiate sleep. Raphe system activity is modulated somewhat
by an adjacent structure called the locus coeruleus. Abnormal
functioning of this structure has been linked with depression and anxiety.
The largest structure in the metencephalon is the cerebellum, which
branches off from the base of the brain and occupies a considerable space in
the back of the head. The cerebellum’s primary function is the learning and
control of coordinated perceptual-motor activities. Learning to walk, run,
jump, throw a ball, ride a bike, or performany other complex motor activity
causes chemical changes to occur in the cerebellum that result in the construction
of a sort of program for controlling the muscles involved in the
particular motor skills. Activation of specific programs enables the performance
of particular motor activities. The cerebellum is also involved in
other types of learning and performance. Learning language, reading, shifting
attention from auditory to visual stimuli, and timing (such as in music or
the tapping of fingers) are just a few tasks for which normal cerebellar functioning
is essential. People diagnosed with learning disabilities often are
found to have abnormalities in the cerebellum.
causes chemical changes to occur in the cerebellum that result in the construction
of a sort of program for controlling the muscles involved in the
particular motor skills. Activation of specific programs enables the performance
of particular motor activities. The cerebellum is also involved in
other types of learning and performance. Learning language, reading, shifting
attention from auditory to visual stimuli, and timing (such as in music or
the tapping of fingers) are just a few tasks for which normal cerebellar functioning
is essential. People diagnosed with learning disabilities often are
found to have abnormalities in the cerebellum.
ment (REM) sleep. REM sleep is characterized by repeated horizontal eye
movements, increased brain activity, and frequent dreaming. The reticular
system (sometimes called the reticular activating system, or RAS) stretches
from the pons through the midbrain to projections into the cerebral cortex.
Activation of the reticular system, by sensory stimulation or thinking, causes
increases in arousal and alertness in diverse areas of the brain. For the brain
to pay attention to something, there must be activation from the reticular
formation. The raphe system, like the reticular system, can increase the
brain’s readiness to respond to stimuli. However, unlike the reticular formation,
the raphe system can decrease alertness to stimulation, decrease sensitivity
to pain, and initiate sleep. Raphe system activity is modulated somewhat
by an adjacent structure called the locus coeruleus. Abnormal
functioning of this structure has been linked with depression and anxiety.
The largest structure in the metencephalon is the cerebellum, which
branches off from the base of the brain and occupies a considerable space in
the back of the head. The cerebellum’s primary function is the learning and
control of coordinated perceptual-motor activities. Learning to walk, run,
jump, throw a ball, ride a bike, or performany other complex motor activity
causes chemical changes to occur in the cerebellum that result in the construction
of a sort of program for controlling the muscles involved in the
particular motor skills. Activation of specific programs enables the performance
of particular motor activities. The cerebellum is also involved in
other types of learning and performance. Learning language, reading, shifting
attention from auditory to visual stimuli, and timing (such as in music or
the tapping of fingers) are just a few tasks for which normal cerebellar functioning
is essential. People diagnosed with learning disabilities often are
found to have abnormalities in the cerebellum.
causes chemical changes to occur in the cerebellum that result in the construction
of a sort of program for controlling the muscles involved in the
particular motor skills. Activation of specific programs enables the performance
of particular motor activities. The cerebellum is also involved in
other types of learning and performance. Learning language, reading, shifting
attention from auditory to visual stimuli, and timing (such as in music or
the tapping of fingers) are just a few tasks for which normal cerebellar functioning
is essential. People diagnosed with learning disabilities often are
found to have abnormalities in the cerebellum.
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