Diencephalon Flashcards
What is the largest portion of the diecephalon?
Thalamus
What makes up the thalamus?
complex group of nuclei
Where is the thalamus located?
interposed between the cortex and lower centers of the brainstem
What three major systems is the thalamus involved with?
Sensory, motor, and reticular formation.
Where sensory information does the thalamus receive and what does it do with this information?
Receives ascending sensory information form sensory pathways, processes this information and relays it to the cortex.
With what systems does thalamus interact with for motor information?
Intimately associated with the motor systems - in particular with the basal ganglia, cerebellum, and motor cortex.
How is the thalamus involved with the reticular formation?
It is a part of the reticular activating system.
What shape are the thalami, how many are there, and where are they located?
Two thalami which are egg shaped nuclear masses, one on each side of the third ventricle.
With with cortex do the thalami function with?
Function with respect to reciprocal connections with the ipsilateral cortex.
What are the fiber layers of the thalamus?
Internal and external medullary lamina
What are the nuclear subdivisions of the thalamus? (6)
- Anterior Group
- Medial Group
- Lateral Group
- Metathalamic Group
- Intralaminar Group
- Reticular Coat
What is the function of the Anterior Group nuclear subdivision of the thalamus?
related to the limbic system
What is the function of the Medial Group nuclear subdivision of the thalamus?
related to a number of systems, but primary access to prefrontal cortex.
Medial Group
-limbic, association cortex, basal ganglia
Dorsomedial Nuc.
-major one
What is the function of the Lateral Group nuclear subdivision of the thalamus?
relay nuclei for somatosensory and motor cortical areas
Dorsal Tier
-Pulivar
Ventral Tier
-VPM, VPL, VL, VA (nuclei for relaying sensory and motor information
What is the function of the Metathalamic Group nuclear subdivision of the thalamus?
Lateral and Medial Geniculate Nucleus
What is the function of the Intralaminar Group nuclear subdivision of the thalamus?
Centromedian nucleus that is related to the reticular formation.
What is the function of the Reticular Coat nuclear subdivision of the thalamus?
Outermost shell of the thalamus (not a part of the reticular formation), acts as gating efferent thalamic information
What are subcotical afferents to thalamic nuclei?
sensory pathways, basal ganglia, cerebellum, reticular formation.
What are the 4 main functions of the thalamus?
- Gates relay for transmission of all sensations (except olfaction) for conscious perception.
- Chief integrating center of all sensory information.
- Plays dominant role in maintenance and regulation of the state of consciousness, alertness and attention = awareness; area of affect-deals with emotion, pain, agreeablness; highly subjective.
- Integrative center for motor activity - basal ganglia and cerebellum
What are the 3 functional groupings of thalamic nuclei?
- Cortical Relay Nuclei
- Assocation Nuclei
- Nonspecific Nuclei
What is the function of Cortical Relay Nuclei? What do they receive and where do they project? What are they?
Receive highly ordered sensory and motor information
and then relay it in an accurate manner (maintaining topographic, tonotopic, visuotopic organization) to specific sensory and motor cortices.
VPM, VPL, VA, VL, LGN, MGN
What is the function of Association Nuclei? What do they receive and where do they project? What are they?
Receive little or no direct afferent from sensory/motor pathways, but have extensive interthalamic connections and receive afferents from other subcortical nuclei (limbic, etc.)
Project back to association cortices (mostly frontal, parietal and temporal lobes)
includes pulvinar, dorsomedial
What is the function of nonspecific nuclei?
intralaminar nuclei (centeromedian) associated with behavioral arousal and sensory/motor integration, sleep.
Reticular thalamic nucleus functions as inhibitory feedback regulator of thalamic neuronal activity-gating of sensory information.
Thalamic pain syndrome origin?
usually vascular in origin; thalamogeniculate artery.
