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The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS).* The CNS contains the brain and spinal cord, while the PNS involves the spinal and cranial nerves and ganglia, the autonomic nervous system. Understanding neuroanatomy is critical to understanding brain functioning. Figure 3–1 illustrates the gross anatomical divisions of the CNS.


Gross anatomical divisions of the CNS. The cerebral hemispheres are found at the rostral end of the nervous system. The basal ganglia are contained within the cerebrum. The midbrain, pons, and medulla oblongata together are called the brainstem, and caudal to that is the spinal cord. Rostral to the midbrain is the diencephalon, the thalamus, and the hypothalamus, which, together with the cerebrum, is called the forebrain. In this scheme (forebrain, midbrain, and hindbrain), the midbrain is itself, and the hindbrain is the pons, medulla, and cerebellum. (Adapted with permission from Kandel ER, Schwartz JH, Jessell TM, et al. Principles of Neural Science, 5th ed. New York, NY: McGraw Hill; 2013. Box 1–1.)

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High-Yield Terms to Learn
Amyotrophic lateral sclerosis (ALS) A slow, progressive, asymmetric atrophy with muscular weakness and hyperreflexia.
Asthenia Debility; loss of strength and energy; weakness.
Ataxia Failure of muscular coordination; irregular and incoordination of movements.
Athetosis Involuntary repetitive, slow, writhing movements. Graphesthesia Tactile ability to recognize writing on the skin.
Barognosis Conscious perception of weight; able to differentiate the weight of objects.
Brain tumor A mass or growth of abnormal cells in the brain.
Cerebrovascular accident/stroke An interruption of blood flow within brain blood vessels, which can be a narrowing or blockage of the vessel (ischemia) or a rupture of a vessel (hemorrhage).
Clasp-knife rigidity Seen in Parkinson disease; increased tension in the extensor of the joint when passively flexed, giving way suddenly on exertion of further pressure; seen in upper motor neuron disease.
Clinical practice guideline (CPG) Recommendations based on the systematic review and evaluation of research evidence used to guide best practices for a specific condition.
Clonus Involuntary muscular contraction and relaxation in rapid succession, initiated by the spinal cord below an area of spinal cord injury. Set in motion by reflexive movements.
Dysdiadochokinesia Impairment of the ability to perform rapid alternating movements.
Dysmetria An aspect of ataxia, in which the ability to control distance, power, and speed of an act is impaired.
Dystonia Impairment of muscular tonus; abnormal muscle tone.
Fasciculation Visible, small, involuntary muscular contraction under the skin; seen lower motor neuron disease.
Graphesthesia Tactile ability to recognize writing on the skin.
Guillain–Barre syndrome (GBS) A group of neuropathic conditions affecting the peripheral nervous system, causing progressive weakness due to motor neuropathy and diminished or absent reflexes.
Hemiballismus Violent motor restlessness of half of ...

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