Diencephalon Flashcards
What makes up the diencephalon?
Thalamus
Subthalamus (sub-thalamic nucleus)
Hypothalamus
What divides the thalamus and into what?
3rd ventricle
Into L and R thalamus
Where is the thalamus situated?
Sits ventral to the lateral ventricles (basal ganglia seen dorsally)
How is the thalamus organised?
Organised into a collection of discrete/individual nuclei
Each nuclei has a separate function & connection w ipsilateral forebrain structures
Internal capsule?
Separates thalamus from the caudate nucleus
Function of the thalamus?
Relay centre between cerebral cortex & other parts of the CNS
Integrates/modulates info. en route
What is an exception to thalamic function?
Involved in ALL sensory systems (except olfactory [smell])
Key relay centre to cortical sensory areas - enhances OR restricts signals
Where is the primary somatosensory cortex found?
Postcentral gyrus (just behind central sulcus) in the parietal lobe
E.g. specific thalamic nuclei involved in the somatosensory pathway?
Ventral posterior lateral nucleus
What can the thalamus nuclei be classed as?
SAIR
Specific - connected to 1o cortical areas
Association - connected to association cortex
Intralaminar - connected to ALL cortical areas
Reticular - NOT connected to the cortex
Structures associated with intralaminar nuclei?
Project to various medial temporal lobe structues
x Amygdala (inferior part of temporal lobe) - emotions, fear, anxiety x Hippocampus (behind amygdala, lying on floor) - memory x Basal ganglis (subcortical area) - movement
Type of neurones associated with intralaminar nuclei?
Glutamatergic neurones
i.e. excitatory!
What can a loss of neurones in the intralaminar nuclei cause?
Associated with
x PSP (progessive supranuclear pasly) - problems w. walking & balance
x Parkinsons disease
What is the reticular nucleus?
Forms the outer covering of the thalamus
Type of neurones associated with reticular nucleus?
GABAergic i.e. inhibitory
What is different about the reticular nucleus compared to other thalamic nuclei?
They do NOT connect w distal regions BUT with OTHER thalamic nuclei
What is the function of the reticular nucleus?
Receives input from thalamic nuclei axons
SO
acts to modulate thalamic activity (-ve feedback)
What is the reticular formation?
Set of interconnected pathways in the brainstem - sends ascending projections to the forebrain nuclei
What is the reticular formation invovled in?
Consciousness and arousal
Degree of wakefulness depends on ARAS activity
What is ARAS?
Ascending reticular activating system
What makes up ARAS?
Reticular formation
Intralaminar nuclei
Reticular nucleus
What divides the hypothalamus?
3rd ventricle - divided into L and R
What is the hypothalamus?
Each side is a collection of individual nuclei with distinct functions
Largerly ipsilateral connection with other nuclei
What are the hypothalamus involved in?
Fighting
Fleeing
Feeding
Mating
3 functions of the hypothalamus?
Coordinates homeostatic mechanisms by:
x regulating ANS via connections w. spinal cord
x connections w endocrine systems e.g. pg
x controlling behaviours via connections w. forebrain structures
Paraventricular nuclei?
Involved in feeding behaviours - recieves input from the arcuate (infundibular) nuclei in the hypothalamus
Sends projections to ANS and posterior P.G
What can PVN lesions cause?
Hyperphagia - abnormal increased desire for food
Weight gain
Suprachiasmatic nucleus?
Directly above the optic chiasm
Responsible for controlling circadian rhythm
Pineal gland?
Said to be invovled in the secretion of melatonin which helps regulate sleep patterns
