Anatomy of the cerebral cortex

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Anatomy of the cerebral cortex

USMLE® Step 1 questions

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Figure 1: Lobes of the cerebrum, lateral view, with inset showing insular lobe deep to lateral fissure.
Figure 2: Brodmann areas of the cerebral cortex, A. Lateral view and B. Medial view.
Figure 3: Gyri and sulci of the lateral surface of the cerebrum.
Figure 4:  Gyri and sulci of the medial surface of the cerebrum.
Figure 5:  Anatomy of the cerebrum, superior view, with the corpus callosum dissected out.
Figure 6: Coronal section of the cerebrum at the level of the anterior commissure.


USMLE® Step 1 style questions USMLE

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A 73-year-old woman develops weakness in the right hand following a stroke. Grip strength is 3/5 in the right hand and 5/5 in the left hand. The lower extremities are unremarkable. A coronal cross-section of the brain is shown below:

Which of the following regions of the motor homunculus is most likely affected in this patient?


Now, we know what you are thinking. Don’t worry, here at Osmosis we are not telepathic, but by watching this video on the cerebral cortex, we know you have the brain on your mind, so let’s get to it!

The human central nervous system basically consists of the spinal cord and the brain, which includes the cerebrum, diencephalon, cerebellum, and brainstem.

Taking a closer look at the cerebrum, it consists of two nearly symmetrical halves, called the cerebral hemispheres, and the basal ganglia, also referred to as basal nuclei. Furthermore, each cerebral hemisphere is divided into four main lobes, the frontal, parietal, temporal, and occipital, as well as what has become to be known as the fifth lobe, the insula, or insular cortex.

If we were to cut through the cerebral hemispheres in the coronal plane, which means transecting from left to right and dividing the brain into rostral and caudal divisions, we would see the cerebral cortex. This is the outermost area of the cerebral hemispheres, and is composed of gray matter containing billions of nuclei, or neuronal cell bodies.

A cell body and its dendrites, along with its axon and synaptic terminal, collectively make-up a structure called a neuron. Neurons thus allow for information processing and communication with other neurons within the nervous system. The gray matter gets its name from its dark appearance during gross inspection.

Deep to the gray matter is the subcortical white matter, which is made up of myelinated axons connected to the nuclei of the gray matter. White matter gets its name because the myelination of the axons gives this area a white appearance on gross inspection.

The largest white matter tract is the corpus callosum, which sends signals between the two cerebral hemispheres essentially connecting them together.


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