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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 26 02 Thalamus Below
Begin 26 02 Thalamus Transcription
Ok, let’s move on to section five. The thalamus.
The thalamus is the largest division of what structure?
- The diencephalon.
The thalamus receives its largest input from what part of the brain?
- From the cerebral cortex.
And the thalamus projects to three main areas.
What are the three main areas of the brain that the thalamus projects to?
- To the cerebral cortex, to the basal ganglia, and to the hypothalamus.
The pathway between the thalamus and these three areas, the cerebral cortex, basal ganglia, and the hypothalamus runs through what two areas or structures?
- Through the internal capsule and the thalamic radiation.
Now the thalamus is divided into three main regions, by what structure?
- By the internal medullary lamina.
Student doctor, please list these three main regions of the thalamus. The anterior, medial, and lateral thalamus.
First we’re going to look at the organization of the thalamus. Please refer to figure 5.1 for the following questions.
In which part of the thalamus are there afferent connections with the amygdala and the prefrontal cortex?
- In the medial thalamus.
And where in the thalamus are there afferent connections from the pulvinar and output to cortex?
- The lateral dorsal and lateral posterior thalamus.
And where in the thalamus are the afferent connections from the basal ganglia located?
- In the ventral anterior nuclei.
Let’s look at the medial lemniscus, which involves touch, proprioception, and so on, where are its afferent connections to the thalamus?
- Ventral posterolateral.
Where in the thalamus does cranial nerve V for taste sensation have afferent connections?
- Ventral postero medial.
And where in the thalamus are the afferent connections from the cerebellum located?
- Ventral lateral
And where in the thalamus are there afferent connections from the auditory apparatus?
- Medial geniculate body.
And where in the thalamus are there afferent connections from the retina?
- Lateral geniculate body.
By the way the medial and lateral geniculate bodies in terms of location are what type of thalamic nuclei?
- Both are posterior nuclei.
And where in the thalamus are there afferent connections from the limbic system?
- In the anterior thalamus.
And input into the limbic system in the anterior thalamus is via what structure?
- The mammillary bodies.
And output from the limbic sysem from the anterior thalamus is via what structure?
- The cingula.
Now let’s take a look at a few clinical correlations. An occlusion to the lenticulostriate branches of the middle cerebral artery can result in an infarction of the internal capsule. Student doctor, please pause if you wish and list five results of such a lesion. Contralateral anesthesia, tactile hyperesthesia, hemiparesis, lower facial weakness, and homonymus hemianopia.
Again, an occlusion of which branch of the middle cerebral artery can result in an infarction of the internal capsule?
- An occlusion of the lenticulostriate branches of the middle cerebral artery.
An occlusion of the posterior thalamoperforating artery results in the thalamic syndrome. Student doctor, what are the three primary clinical features of the thalamic syndrome?
- First, contralateral hemiparesis. Second, contralateral hemianesthesia. And third, both elevated pain threshold and spontaneous pain.
To review the mechanism of injury, an occlusion of which artery results in the thalamic syndrome?
- The posterior thalamoperforating artery.
****END OF TRANSCRIPTION****
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