Diencephalon & Telencephalon Flashcards
Forebrain
Diencephalon & Telencephalon
Diencephalon
thalamus & hypothalamus (80% - master of control of nervous and endocrine system)
- retina is an extension of diencephalon
3rd ventricle
Telencephalon
cerebral hemispheres
• cerebral cortex (outer covering of grey matter)
• basal nuclei
• limbic structures (hippocampus & amygdala)
• white matter
lateral ventricle
hypothalamic sulcus
separates thalamus from the hypothalamus
subthalamus
•inferior to the thalamus
•Superior to tegmentum of mesencephalon (cranial ends of red nucleus & substantia nigra)
Function:
Related to the basal nuclei & motor pathway
Location / structures that border the Diencephalon:
Medial: Lateral: Superior: Inferior: Rostral:
3rd ventricle
posterior limb of the internal capsule
bodyofthelateralventricles
mesencephalon, subarachnoid space rostral interventricular foramen, anterior commissure, lamina terminalis & optic chiasm
Thalamus
= 80% of the diencephalon
= paired structure!
“the gatekeeper” - prevents or enhances the passage of information to the cerebral cortex
all sensory info. except smell goes through thalamus first before cortex
- has numerous nuclei with different functions
•The basal nuclei & cerebellum (motor) communicate with the cortex via the thalamus
•Regulates flow of information between different areas of the cortex
•Bidirectional communication with cortex
The Y-shaped internal medullary lamina (white matter) divides the thalamus into:
- Anterior nuclei = anterior nucleus
- Medial nuclei = dorsomedial nucleus
- Lateral nuclei
- Posterior nuclei = medial & lateral geniculate nuclei (MGN & LGN)
- Intralaminar nuclei = {centromedian (CM) & parafascicular nuclei}
- Thalamic reticular nucleus (TRN) - neurons come in and out through TRN
Lateral nuclei - dorsal tier
- lateral dorsal (LD)
- lateral posterior (LP)
- Pulvinar (PUL)
Lateral nuclei - ventral tier
ventral anterior (VA)
• Ventral lateral (VL)
• Ventral posterior (VP) – VP lateral (VPL) & VP medial (VPM)
Thalamic RELAY Nuclei:
relay input (sensory, motor or limbic) from periphery to a specific area of the cortex Receive specific input fibres & project to specific cortical areas
motor: VA, VL
sensory: VPM - head
VPL - somatosensory from body
MGN - relay nucleus from auditory
LGN- visual
limbic: Ant, LD, DM (motions, memory/learning)
Thalamic ASSOCIATION Nuclei:
regulates the interaction between cortical areas
receive most of their input from cortical areas
Dorsomedial - prefrontal cortex
Pulvinar / LP - parietal-occipital-temporal association cortex
Thalamic nuclei
ALL thalamic nuclei (except reticular nucleus)
Possess reciprocal connections with the ipsilateral cerebral cortex
Thalamic reticular nucleus (TRN)
Unlike all other thalamic nuclei, the TRN does not project to the cerebral cortex! - monitors thalamic activity to cortex
* Axons travelling from thalamus to cortex OR from cortex to thalamus have collaterals to the TRN Regulates thalamic activity
Thalamus pathway
driver info to thalamus > thalamus relays info to cortex > cortex sends feedback on this info to the TRN > TRN can inhibit the area of thalamus from which the initial info came ; this can block flow from the thalamus to cortex
