The Diencephalon Flashcards
What is the diencephalon made up of
Thalamus
Subthalamus
Hypothalamus
Describe the thalamic organisation
Sits ventral to the lateral ventricles
Thalamus is divided in two by the 3rd ventricle
Organised into discrete nuclei
What is the thalamus made up of (?)
Anterior nuclear group Ventral anterior nucleus Lateral dorsal nucleus Ventral lateral nucleus Lateral posterior nucleus Ventral posterior lateral nucleus Ventral posterior medial nucleus Midline thalamic nuclei Medial nuclear group Intralaminar nuclei Internal medullary lamina Pulvinar Medial geniculate nucleus Lateral geniculate nucleus
What are the key functions of the thalamus
Relay site for numerous inputs/outputs
Key relay centre to cortical sensory areas
Involved in almost all sensory systems (except olfactory)
Enhances or restricts signals
Involved in the somatosensory pathway
What are the intralaminar nuclei
Projects to various medial temporal lobe structures (e.g. amygdala, hippocampus and basal ganglia)
Mostly glutamatergic neurons (excitatory)
What are the functions of the amygdala, hippocampus and basal ganglia
Amygdala = emotions, fear, anxiety
Hippocampus = memory
Basal ganglia = movement
What are loss of neurons in the intralaminar nuclei associated with
Progressive supra nuclear palsy and Parkinson’s
PSP = brain disorder causes problems with walking and balance
What is the reticular nucleus
Forms the outer covering of the thalamus
Majority are GABA (inhibitory)
Do not connect with distal regions, do with other thalamic nuclei
Receive inputs from collaterals of their axons from thalamic nuclei
Modulates thalamic activity
What is the reticular formation
Set of interconnected pathways in the brainstem that sends ascending projections to the forebrain nuclei (ascending reticular activating system, ARAS)
Involved in consciousness and arousal
Degrees of wakefulness depend on ARAS activity
What is the relationship between the intralaminar nuclei, reticular nucleus and reticular formation
Both intralaminar and reticular nucleus receive inputs from ARAS
Describe the hypothalamus
Divided into two by the third ventricle
Collection of individual nuclei with distinct functions
Largely ipsilateral connections with other nuclei
What is the hypothalamus involved in
Fighting
Fleeing
Feeding
Mating
What is the function of the hypothalamus
Direct connections with the autonomic nervous system
Neurons in the hypothalamic paraventricular nucleus with direct projections to pre-autonomic neurons in the spinal cord
Connections with the endocrine systems e.g. hypothalamic-pituitary axis
Control of behaviour e.g. feeding
What is the paraventricular nucleus
Cluster of neurons with similar functions and connections
Sends projections to autonomic nervous system and posterior pituitary gland via parvocellular and magnocellular neurons respectively
Involved in feeding behaviour(particularly PVN)
Where is the suprachiasmatic nucleus
Above the pituitary gland
