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Let’s start our USMLE Review with Anatomy from the Gold Standard USMLE Step 1 Audio Review program.
Play USMLE Audio MP3 25 02 Intro to Neuroanatomy Below
Begin 25 02 Intro to Neuroanatomy Transcription
Neuroanatomy is a very high yield topic in the anatomy section in the USMLE Step I questions. On every step I exam there are questions on the functions of the various regions of the brain as well as of the clinical features of various brain, cranial nerve, or spinal cord lesion.
I. Embryologic development of the nervous system.
The nervous system begins development during which week of embryonic development?
- During the third week.
Student doctor, what embryonic structure develops into the central nervous system beginning its development in the third week?
- The neural tube.
The neural tube gives rise to the central nervous system, which is composed of which two main parts?
- The brain and the spinal cord.
Now, the neural tube divides into three main divisions during which week?
- During the fourth week of embryonic development.
And during the fourth week the neural tube divides into three main divisions due to what two flexures?
- Due to the midbrain and cervical flexures.
Now the three main divisions of the neural tube that arise during the fourth week due to the midbrain and cervical flexures are called the three primary brain vesicles. Please refer to figure 1.1.
What are the names of these three primary brain vesicles?
- The prosencephalon, the mesencephalon, and the rhombencephalon.
Now once the three primary brain vesicles are formed, the prosencephalon, the mesencephalon, and the rhombencephalon, during what week are the five secondary brain vesicles formed in the neural tube?
- During the fifth week.
Student doctor, please name the two secondary brain vesicles that are derived from the prosencephalon. Refer to figure 1.2. These are the telencephalon and the diencephalon.
During the fifth week of development, which of the primary brain vesicles remains itself?
- Mesencephalon. It remains as the mesencephalon.
However, the rhombencephalon gives rise to two secondary brain vesicles. Student doctor, name the two secondary brain vesicles derived from the rhombencephalon. Refer to figure 1.3. The metencephalon and the myelencephalon.
Now the secondary brain vesicles give rise to various adult derivatives. Student doctor, what are the adult structures derived from the walls and what of the cavity of the telencephalon?
- The walls of the telencephalon give rise to the cerebral hemispheres while the cavity of the telencephalon gives rise to the lateral ventricles.
Now we take a look at the diencephalon to refresh our memory. Where does the diencephalon come from?
- The diencephalon is one of the two secondary brain vesicles derived from the prosencephalon.
What are the adult structures derived from the walls of the diencephalon andfrom the cavity of the diencephalon?
- The walls of the diencephalon gives rise to four structures: the thalamus, the hypothalamus, the epithalamus, and the subthalamus, while the cavity of the diencephalon gives rise to the third ventricle, keeping in mind that the mesencephalon does not give rise to secondary vesicles but remains itself during the fifth week of embryonic development.
Student doctor, what is the adult brain structure derived from the walls of the walls of the mesencephalon and of the cavity of the mesencephalon?
- The walls of the mesencephalon give rise to the midbrain, while the cavity of the mesencephalon gives rise to the cerebral aqueduct.
Student doctor, what are the adult structures derived from the walls of the metencephalon and the cavity of the metencephalon?
- The walls of the metencephalon give rise to the pons and the cerebellum, while the cavity of the metencephalon gives rise to the superior part of the fourth ventricles.
And what are the adult structures derived from the walls of the myelencephalon and the cavity of the myelencephalon?
- The walls of the myelencephalon give rise to the medulla oblongata, while the cavity of the myelencephalon gives rise to the inferior part of the fourth ventricles.
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