Overview of the Central Nervous System (Gross Anatomy of the Brain) Part 4

Clinical Case

The following clinical case is intended to illustrate some of the basic neuroanatomical concepts presented in this topic. You are not expected to diagnose the patient’s condition or suggest any therapy or medical steps to be taken. Rather, we hope that this case and those that follow will demonstrate the very real clinical relevance of basic neuroscience information.


Saul is a 75-year-old man who recently learned from his internist that he had an irregular heartbeat. He was prescribed medication to regulate his heart rate and asked to return in a few days, but he was too frightened to fill the prescription or return for the appointment. One morning, 3 weeks after seeing his physician, he awoke and, upon attempting to get out of bed, was unable to move his left arm and leg. Using his right hand, he dialed 911. When the operator answered, he attempted to explain his problem, but his speech was so slurred that the operator could not understand him.The operator told him to remain on the line so that the call could be traced. An ambulance arrived shortly afterward, and Saul was taken to the nearest emergency room (ER).


The ER staff noted Saul’s irregular heartbeat. A neurologist arrived and confirmed that, although Saul’s speech was quite slurred, much like that of an inebriated person, his sentences were grammatically correct and everything he attempted to say made logical sense. His blood alcohol level was 0.0. He could follow three-step commands and repeat statements, despite his slurred speech. When he tried to smile, his mouth drooped on the left side. But when he wrinkled his eyebrows, his forehead remained symmetric. His left arm was completely paralyzed, but he was able to wiggle his left leg minimally.Saul was admitted to the intensive care unit for treatment.


Saul’s abnormal heartbeat is called atrial fibrillation, a rhythm characterized by irregularity and, typically, rapidity. It can cause strokes by dislodging small dots from the heart and causing them to travel as emboli to the cerebral blood vessels, causing occlusion.

Saul’s condition is an example of a right frontal lobe cortical stroke involving the precentral gyrus or the primary motor cortex.The motor problems, including the slurred speech and arm and leg weakness, occurred because of involvement of these areas. This region is functionally organized as a homunculus, with representation of each region of the body in specific locations.The effects can be attributed mainly to occlusion of the middle cerebral artery (a branch of the internal carotid artery and a common location for emboli) because this artery subserves most of the affected region. However, the superior portion of this region is partially within the territory of the anterior cerebral artery. Clinically, this is demonstrated by the fact that the patient’s leg is somewhat involved but not as extensively as his arm. Although there is weakness of the lower two thirds of the face, the forehead is not involved because of bilateral cortical innervation of this region. Because the majority of people are right-handed with left-sided cerebral dominance (the side where language originates), Saul’s language disturbance is solely motor, and he is able to follow commands and construct sentences. Saul was transferred from the ER to another section of the hospital. After remaining in the hospital for approximately 4 weeks, he was sent to a nearby rehabilitation facility where he was able to regain most of his basic motor functions, including speech.


Overview of the Major Structures of the Brain and Their Functions

Brain Region


General Functions

Associated Disorder(s)

Cerebral Cortex

Frontal lobe

Precentral gyrus

Voluntary movement of muscles of body and head region

Loss of voluntary movement of body and head region

Premotor region

Aids and integrates voluntary movements of body

Apraxia (loss of ability to carry out complex movements of body and head)

Frontal eye fields

Controls voluntary horizontal movement of the eyes

Loss of voluntary control of horizontal eye movement (i.e., eyes cannot deviate to side opposite lesion)

Prefrontal cortex

Intellectual functions;affective processes

Intellectual and emotional impairment

Broca’s motor speech area

Regulates motor aspects of speech

Motor aphasia

Parietal lobe

Postcentral gyrus

Conscious perception of som-esthetic sensation

Loss of somatosensory perception

Wernicke’s area

Receptive integration of speech

Receptive aphasia

Superior parietal lobule

Integration of sensory and motor functions; programming mechanism for motor responses

Posterior parietal syndrome; sensory neglect; apraxia

Temporal lobe

Superior temporal gyrus

Auditory perception

Loss of auditory perception

Middle temporal gyrus

Detection of moving objects

Loss of movement detection

Inferior temporal gyrus

Recognition of faces

Loss of facial recognition

Occipital lobe

Upper and lower banks of calcarine sulcus

Visual perception

Partial or total loss of vision of the contralateral visual fields for both eyes, depending upon the extent of the lesion in the visual cortex

Deep Brain Structures


Ventricles of the brain

Lateral, third, and fourth ventricles and cerebral aqueduct

Flow of CSF throughout the CNS: a source of electrolytes and conduit of neuroactive and metabolic products


Basal ganglia

Caudate nucleus, putamen, globus pallidus, subthalamic nucleus, substantia nigra

Regulation of motor functions associated with cerebral cortex


Brain Region


General Functions

Associated Disorder(s)



Thalamic nuclei

Transmission of signals from other regions of the CNS to the cerebral cortex mediating sensory, motor, cognitive, and affective (emotional) functions

Disruption and possible loss of sensory, motor, and other functions


Hypothalamic nuclei

Visceral (feeding,drinking, autonomic, and endocrine functions and sexual and emotional behavior)

Disruption, loss, or alterations in visceral and affective functions and processes

Limbic structures

Hippocampal formation, amygdala, septal area,cingulate gyrus, prefrontal cortex

Modulation of hypothalamic functions; regulation of emotional behavior; short-term memory

Temporal lobe epilepsy; loss of control of emotions and related affective processes; loss of short-term memory

Cerebellum and Brainstem

Cerebellum: anterior, posterior, and flocc-ulonodular lobes

Integration of motor functions related to all regions of the CNS associated with motor and related processes

Loss of balance; ataxia; hypotonia; loss of coordination; disorders of movement when intentionally attempting to produce a purposeful response


Transmission and regulation of sensory, motor, and autonomic functions (cranial nerves III and IV)

Sensory, motor, and autonomic deficits as well as deficits associated with cranial nerves III and IV


Transmission and regulation of sensory, motor, and autonomic functions (cranial nerves V, VI, and VII)

Sensory, motor, and autonomic deficits as well as deficits associated with cranial nerves V,VI,and VII


Transmission and regulation of sensory, motor, and autonomic functions (cranial nerves VIII, IX, X,XII)

Sensory, motor, and autonomic deficits, including respiration, as well as deficits associated with cranial nerves VIII, IX, X, and XII

CNS = central nervous system; CFS = cerebrospinal fluid.

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