CENTRAL NERVOUS SYSTEM DRUGS
Section I. THE CENTRAL NERVOUS SYSTEM
PARTS OF THE CENTRAL NERVOUS SYSTEM
The central nervous system (CNS) includes the brain and spinal cord. It is
divided into the following levels based on anatomical position and function.
a. Cerebrum. The cerebrum consists of two hemispheres and contains the
cerebral cortex, which is the site of consciousness, memory, sensation, some
conditioned reflexes, and inhibition of certain reflexes. Nerve fibers extend to the lower
portion of the brain and spinal cord. Transverse fibers connect the two hemispheres.
b. Midbrain (Mesencephalon). The midbrain carries pathways that connect
the cerebrum and lower parts of the brain and the spinal cord. It also contains the
thalamus and hypothalamus portion of the brain. Visual and audio reflexes are
received here. Movement of the head and eyes in response to retinal stimuli originates
c. Pons. The pons is that part of the brain stem that is behind the midbrain and
above the medulla oblongata. It carries various nerve pathways. The pons is
connected with all portions of the brain.
d. Medulla Oblongata. The medulla is an oblongated portion at the base of the
brain, which can be considered an upward continuation of the spinal cord. It contains
the "vital centers"--the cardiac, vasomotor, and respiratory control centers--as well as
controls for swallowing, vomiting, and coughing.
e. Cerebellum. The cerebellum, situated behind the brain stem (midbrain,
pons, and medulla), is concerned with voluntary movements, although it plays no part in
initiating them. Removal of the cerebellum would cause lack of muscular control, with
f. Spinal Cord. The spinal cord contains a central mass of gray matter
surrounded by columns of white matter, which are bundles of nerve fibers. The cord
serves as a reflex center and provides a series of ascending and descending pathways
to and from the brain.
(1) Ascending. The ascending pathways carry stimuli of conscious muscle
sense, pain, heat, and cold.