Diencephalon Flashcards
Where is the Thalamus located?
In the middle of the brain just under the posterior half of the Corpus Callosum
What are the parts of the diencephalon?
Thalamus
Subthalamus
Hypothalamus
What is the structure present within the Thalamus?
The 3rd Ventricle - Divides thalamus in two
What are Neuroanatomical Nuclei?
Clusters of neurones with similar functions and connections
What is contained in the Thalamus?
Collection fo individual nuclei with separate but interconnected functions
They have Ipsilateral connections with the forebrain
(Also 3rd ventricle)
(Note picture is the Left Thalamus)
What is the function of the Thalamus?
Relay Centre between the cerebral cortex and the rest of the CNS
Two-way reciprocal connection
There is Integration and Modification of information that passes through
It contains a nucleus for virtually every functional system within the CNS
(Except Olfaction)
How are Thalamic nuclei classified?
Based on the connection of the nuclei with the cortex: SARI
Specific: Connected to primary cortical areas
Association: Connected to association cortex
Reticular: Not connected to the cortex
Intralaminar: Connected to all cortical areas
What ar ethe Thalamic Nuclei connected to the Motor Cortices?
(Primary, premotor and supplementary Cortices)
Ventral Lateral Nucleus
Ventral Anterior Nucleus
What are the two nuclei that relay Somatosensory information?
Ventral Posterolateral (Body)
Ventral Posteromedial (Head)
What do the Lateral geniculate and Medial Geniculate nuclei connect to?
Lateral Geniculate - Visual cortex
Medial Geniculate - Auditory cortex
Label the Functional Cortical Areas
What is the name given to the non-functional cortical areas?
What is it split into?
Association Cortex
Prefrontal Cortex
Parieto-tempero-occipital Cortex
Cingulate cortex
Where is the cingulate cortex?
It sits posteriorly to the corpus callosum and ‘follows it round’
(Can be viewed when looking at the medial surface of the cerebral hemisphere)
What are the thalamic nuclei connected to the areas of the association cortex?
Cingulate + Prefrontal cortices: Anterior, Lateral Dorsal, Dorsomedial
Parieto-temporo-occipital + Prefrontal Cortices: Lateral Posterior, Pulvinar
What is the Reticular Nucleus?
Where is?
What does?
What Neurotransmitter?
Extends over the whole lateral surface of the Thalamus
Has no cortical connections, but connects to nearly all Thalamic Nuclei
GABAergic neurones (inhibitory) that can modulate thalamic activity via negative feedback
Part of the Reticular activating system
Where do the Intralaminar Nuclei project?
What do these structures do?
Amygdala: emotions, fear, anxiety
Hippocampus: memory
Basal Ganglia: movement
What type of neurones are in the Intralaminar Nuclei?
What is associated with their loss?
Glutamatergic neurones (i.e. excitatory)
Progressive supranuclear palsy
Parkinson’s Disease
What is the reticular formation?
What does it do?
Set of interconnected pathways in the brainstem
Send ascending projections to forebrain nuclei:
- Ascending reticular activating system (ARAS)
Involved in consciousness and arousal
Degrees of wakefulness depend on ARAS activity (increased activity = increased wakefulness)
Both intralaminar and reticular nucleus receive inputs from ARAS
Where is the Hypothalamus?
What is in proximity to it?
What divides it?
Lies below the Thalamus
Optic chiasm and pituitary stalk are seen just anteriorly to it
It is divided by the third ventricle
What are the main functions of the Hypothalamus?
Homeostasis via:
ANS
Endocrine system
Behaviour control
(involved in 4 F’s; Fighting, Fleeing, Feeding, Mating)
Which forebrain structures are associated with the Hypothalamus?
Olfactory System
Limbic System (Hippocampus, Amygdala, Cingulate cortex, Septal Nuclei)
Which behaviours are controlled by the Hypothalamus?
Eating and Drinking
Expression of emotion
Sexual behaviour
Circadian Rhythm
Memory
How does the hypothalamus modulate hunger?
The Arcuate nucleus becomes more active when hungry and communicates with the Paraventricular nucleus to reduce levels of satiety peptides/hormones making you go and eat
On what side do Hypothalamic nuclei connect to other nuclei?
Ipsilateral - unlike most nuclei
What are the two cell types in the Paraventricular nuclei?
What do they do?
Magnocellular - Stimulates release of hormones from the pituitary
Parvocellular - Controls autonomic outflow
Label this diagram of the Hypothalamus:
What is the main function of the Suprachiasmatic Nucleus?
Controlling Circadian rhythm
Receives signals about light levels from the eye and connects to the Pineal gland to regulate the production of Melatonin
