Thalamus Flashcards
Components of the diencephalon
Third ventricle, thalamus, sub thalamus, epithalamus, hypothalamus
Boundaries of diencephalon
posterior commissure dorsally to the interventricular foramina ventrally; dorsally bordered by roof of third ventricle, ventrally bordered by optic chasm, infundibulum, and mammillary bodies
What is the only sensory pathway that does not relay through the hypothalamus?
Olfaction
Reticular nucleus receives collaterals from…
both afferent and efferent thalamic axons and projects in turn to the other nuclei of the thalamus
What is the stratum zonale?
Rostral thin white matter layer covering the thalamus
Lateral white matter layer covering the thalamus
external medullary lamina
Y-shaped white matter that divides thalamus into 3 parts
internal medullary lamina
Components of the lateral part of the thalamus
- Dorsal tier
- lateral dorsal nucleus
- lateral posterior nucleus
- pulvinar - ventral tier
- ventral anterior nucleus
- ventral lateral nucleus
- ventral posterior nucleus
- medial and lateral geniculate bodies
reticular nucleus
located on the lateral surface of the thalamus between the external medullary lamina and the internal capsule
Input and output and function anterior nucleus of thalamus
input: hypothalamus (mammillary bodies and mammillothalamic tract)
output: to cingulate gyrus (anterior limb of IC)
function: emotional states and memory, alertness and attention
input, output and function of ventral anterior and lateral nuclei
input: basal ganglia and the cerebellum
output: motor and premotor cortices
function: provide the motor cortex with information received from the cerebellum and basal ganglia
subdivisions of ventral posterior nucleus
- ventroposterolateral nucleus -> somatosensory input related to body from medial leminscal and spinothalamic tract
- ventroposteromedial nucleus -> somatosensory input from the face from sensory nuclei of trigeminal nerve
-both project to primary somatosensory cortex
input, output centromedian nucleus
input: cerebral cortex, globus pallidus
output: projects to caudate and putamen
input, output and function of reticular nucleus
input: collateral branches of thalamocortical and corticothalamic fibers
output: thalamic nuclei
function: modulates influence that thalamus exerts on cortex
name the association thalamic nuclei
medial nucleus (dorsomedial nucleus), lateral dorsal nucleus, lateral posterior nucleus, pulvinar
what cortices do the association thalamic nuclei project to?
1 of 3: parietal-temporal-occipital association cortex, prefrontal association cortex, limbic association cortex
input, output and function of dorsomedial nucleus
input: olfactory cortex, amygdaloid nucleus and hypothalamus
output: prefrontal association cortex
function: affective behavior, mood influences
name the condition that results from dorsomedial nucleus damage
Korsakoffs syndrome -> confabulation, memory loss
input, output and function of lateral dorsal nucleus
input: hippocampal formation
output: cingulate gyrus
function: emotional behavior
input, output of lateral posterior nucleus
input: unknown
output: somatosensory association cortex
input, output and function of pulvinar
input: superior colliculus of midbrain, sensory association areas of parietal, temporal and occipital areas
output: parietal, temporal and occipital association cortices
blood supply thalamus
mostly from the posterior cerebral artery, as well as the posterior communicating artery; additional from anterior and posterior choroidal arteries
specific branches of the posterior cerebral artery that supply the thalamus
thalamopeforate artery and thalamogeniculate artery
thalamoperforating arteries
origin: P1 segment
supply: medial thalamus (mediodorsal and intralaminar nuclei)
thalamogeniculate arteries
origin: P2 segment
supply: lateral thalamus (VL, VPL, VPM, MGB, LGB), and pulvinar
what part of the thalamus does the medial posterior choroidal artery supply?
choroid plexus of 3rd ventricle, pineal gland, superior medial aspect of the thalamus
what part of the thalamus does the lateral posterior choroidal artery supply?
choroid plexus of the lateral ventricles and the lateral nuclear group of thalamus
what part of the thalamus does the anterior choroidal artery supply?
part of the LGB, ventrolateral nuclei and reticular nucleus
what part of the thalamus does the PCOM supply?
perforators to the inferior thalamus
Paramedian Artery of Percheron
single large P1 perforator that perfuses the medial aspect of thalamus (MD nucleus) bilaterally
What sensation characteristic will differentiate a lesion fo the thalamus vs somatosensory cortex?
vibration sense spared in somatosensory lesion; lost in thalamic lesions
ventral anterior nucleus inputs and outputs
input: medial segment of Globus pallidus and substantia pars reticulata
output: frontal eye fields (area 8), premotor cortex, and SMA (area 6)
Thalamic radiations
4 distinct fiber peduncles that communicate the thalamus with the cerebral cortex
thalamic radiation projections
anterior-> frontal lobe
inferior -> temporal lobe
superior -> parietal lobe
posterior -> occipital lobe
where do the thalamic radiations travel?
anterior -> anterior limb of IC
superior -> posterior limb of IC
inferior -> sublenticular region of IC
posterior -> retrolenticular portion of IC
lesions of posterior limb of internal capsule can cause…
- hemiparesis (corticospinal tract)
- hemianesthesia (thalamocortical fibers)
- hemianopsia (optic radiation)
- hemihypacusis (auditory radiation)
neurotransmitters of thalamic projections
glutamate and aspartate
what thalamic nucleus is the only one to use inhibitory NT?
reticular nucleus (GABA)
components of the epithalamus
pineal body, stria medullaris thalami, habenular trigone and the roof (tela choroidea) of the 4th ventricle
Stria medullaris thalami
fibers originate in the septal nuclei, preoptic region of the hypothalamus and the anterior thalamic nuclei -> PROJECTS to habenular nuclei ->project to midbrain via fasciculus retroflexus
what does the pineal gland secrete
melatonin, serotonin, norepinephrine
the suprachiasmatic nucleus of the hypothalamus relays light cycle indirectly to the pineal gland through….
superior cervical ganglion
