CMD 377 Lecture 16: CMD 377 - Lecture 16 - The Diencephalon

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Communicative Disorders
CMD 377
Mikyong Kim

CMD 377 - Lecture 16 - The Diencephalon The Diencephalon ● Divided into 4 parts: ○ Epithalamus ○ Thalamus ○ Subthalamus ○ Hypothalamus The Epithalamus ● The Pineal Gland: ○ Midline structure ■ Only one ○ Endocrine organ involved with reproductive cycles in mammals ■ Unsure about how it works in humans with regards to reproduction though ○ Secretes melatonin ■ Suppresses production of reproductive cells ■ Produced in larger quantities when it’s dark out ● More produced in winter than summer ○ Controls mating cycle in mammals ○ Important in regulation of circadian rhythms ■ Sleep-wake cycle ○ Pineal tumor may cause precocious puberty ■ Puberty comes early The Subthalamus ● Inferior to the thalamus and lateral to the hypothalamus ● Contains part of the: ○ Substantia nigra ○ Red nucleus ● Contains the subthalamic nuclei ○ Interconnected with the basal ganglia ○ Important for motor function The Thalamus ● A large, egg-shaped nuclear mass ● Part of a large number of pathways ○ All sensory pathways relay in the thalamus ■ Except olfaction ○ Anatomical loops comprising of the cerebellar, basal ganglionic, and limbic pathways involve thalamic relay ○ The various systems utilize separate portions of the thalamus ■ Subdivided into a series of nuclei based on location and function Thalamic Nuclei: Examples of Specific Relay Nuclei ● Receive well-defined bundles of fibers and projects to particular functional areas of the cortex ● Sensory relay nuclei include: ○ Ventral posterolateral nucleus (VPL)/ventral posteromedial nucleus (VPM) → output to the somatosensory cortex ■ VPL → somatosensory input from the body (spinothalamic tract, medial lemniscus) ■ VPM → somatosensory input from the head (trigeminal thalamic tract) ○ Geniculate nuclei ■ Lateral geniculate nucleus → visual system ■ Medial geniculate nucleus → auditory system ○ Motor relay nuclei ■ Input from the cerebellum and the basal ganglia ■ Output to the motor and premotor cortex (ventral anterior, ventral lateral) Other Types of Thalamic Nuclei ● Association nuclei ○ Project to association cortices ● Non-specific nuclei ○ Project to extremely widespread areas of the cortex ● Subcortical nuclei ○ No projection to the cerebral cortex Blood Supply of the Thalamus ● Mostly from branches of the posterior cerebral artery (PCA) ● Lesion, especially in the posterior thalamus, can cause thalamic syndrome ○ Thalamic - triggered by sensory stimuli ○ Loss of somatic sensation in the contralateral head and body ■ Hemianesthesia → abolished discriminative tactile sensibility ■ Sensory type ataxia → impaired position sense ● No sensory feedback ● Losing proprioception The Hypothalamus ● Interconnects with various components of the li
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