Thalamus and Hypothalamus Flashcards
Describe the organisation of the thalamus
The thalamus is part of the diencephalon (thalamus, hypothalamus and the sub-thalamic nucleus).
It is divided into left and right thalamus by the third ventricle, each being a collection of individual nuclei with separate functions and connections with ipsilateral (same side or no crossing over) forebrain structures.
The thalamus is separated from the caudate nucleus by the internal capsule
What is the function of the thalamus?
Relay centre between the cerebral cortex and other parts of the CNS.
Integrates/modulates information en route.
Involved in ALL functions except olfaction (smell).
Some nuclei form PART of the Reticular Activating System
What are the classes of nuclei in the thalamus?
Specific – connected to primary cortical areas.
Association – connected to association cortex.
Intralaminar – connected to ALL cortical areas.
Reticular – not connected to the cortex
What areas do the different nuclei in the thalamus connect to?
ventral lateral, ventral anterior -> motor cortices (primary, supplementary, premotor)
ventral posterolateral -> somatosensory (body)
ventral posteromedial -> somatorsensory (head)
lateral geniculate -> visual
medial geniculate -> auditory
What does the intralaminar nuclei project to?
various medial temporal lobe structures e.g. amygdala (emotion, fear anxiety) , hippocampus (memory) and basal ganglia (movement)
mostly glutamatergic neurons
*loss of neurones in region associated with supranuclear palsy and Parkison’s disease
What does the reticular nucleus do?
forms outer covering of thalamus
majority of neurons aar GABAnergic (inhibitory)
don’t connect to with distal regions, but with other thalamic nuclei - modulates thalamic activity (negative feedback)
What is the reticular formation?
set of interconnected pathways in the brainstem - send ascending projections to forebrain nuclei (ascending reticular activating system)
involved in consciousness and arousal - degree of wakefulness depends on ARAS activity
both intralaminar and reticular necleus receive inputs from ARAS
Describe the organisation of the hypothalamus
Located in the diencephalon below the thalamus.
Divided into the left and right hypothalamus by the third ventricle.
Each side is largely a collection of individual nuclei with separate actions and ipsilateral connections with forebrain structures.
Mammillary bodies lie directly below the hypothalamus
What is the function of the hypothalamus?
Co-ordinates homeostatic mechanisms by:
Regulating ANS via connections with the spinal cord.
Acting as an endocrine organ via the pituitary gland.
Controlling behaviour via connections with forebrain structures
What structures is the hypothalamus associated with?
olfactory system
limbic system - hippocampus, amygdala, cingulate cortex and septal nuclei.
behaviour directed towards well-being triggers the reward system in the hypothalamic-limbic circuitry, leading to reinforcement of that behaviour
What behavioural features dos the hypothalamus influence?
- Eating and drinking
- Expression of emotion
- Sexual behaviour
- Circadian rhythm
- Memory
What is the paraventricular nucleus?
in hypothalamus
One of the areas where the axons go from the infundibular nuclei – again involved in feeding (ties closely with oxytocin).
sends projections to ANS and posterior pituitary gland - parvocellular -> synapse in spinal cord -> blood vessels, heart, kidneys/ magnocellular -> posterior pituitary
also involved in feeding behaviour
MC4R mutations and hyperphagia are effects of PVN damage.
SIM1 is involved in development of the hypothalamus and particularly the PVN.
SIM1 deficiency causes syndromic obesity
What is the suprachiasmatic nucleus?
sits above the optic chiasm
oscillatory activity - controlled by blue light - activated retinal ganglion cells
What would a lesion in the SCN cause?
Why is is significant?
lesion in SCN -> fragmented sleep pattern
symptoms of schitzophrenia :
halluciantions, delusions, confused thoughts, loss of motivation, sleep disturbances, lack of concentration
no direct link but there’s evidence (sleep disturv=bances)
