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Lobes of the Brain
The manifestations
of stroke depend on which region and the extent of brain affected.
The three main components of the
brain -- the cerebrum, the cerebellum, and the brain stem -- have
distinct functions. The cerebrum is the largest and most developmentally
advanced part of the human brain. It is responsible for several higher
functions, including higher intellectual function, speech, emotion,
integration of sensory stimuli of all types, initiation of the final
common pathways for movement, and fine control of movement.
The cerebellum, the second largest
area, is responsible for maintaining balance and further control of
movement and coordination.
The brain stem is the final
pathway between cerebral structures and the spinal cord. It is
responsible for a variety of automatic functions, such as control of
respiration, heart rate, and blood pressure, wake-fullness, arousal and
attention.
The cerebrum is divided into a
right and a left hemisphere and is composed of pairs of frontal,
parietal, temporal, and occipital lobes.
The left hemisphere controls the
majority of functions on the right side of the body, while the right
hemisphere controls most of functions on the left side of the body The
crossing of nerve fibers takes place in the brain stem. Thus, injury to
the left cerebral hemisphere produces sensory and motor deficits on the
right side, and vice versa.
One hemisphere has a slightly more
developed, or dominant, area in which written and spoken language
is organized. Over 95% of right handed people and even
the majority of left handed people have dominance for speech
and language in the left hemisphere [Mohr JP, et al: In: Barnett
HJM, et al (eds). Stroke. Pathophysiology, Diagnosis, and
Management. New York, Churchill Livingstone, 1992:331] Thus,
a left hemisphere stroke will be more likely to produce aphasia
and other language deficits.
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Stroke Education
