Thalamus Flashcards
(32 cards)
What does the thalamus stand for?
inner chamber, room
Where is the thalamus derived from?
derived from the embryonic diencephalon.
Where si the thalamus located?
Comprising two halves, the thalamus is positioned
symmetrically on both sides of the third ventricle
Whta do myelinated fibers within th ethalamus do?
form a system that separates clusters of neurons, defining thalamic
subparts.
sensory system within th ebrain is connected where?
Every sensory system, excluding the olfactory
system, is connected to a thalamic nucleus,
responsible for receiving and transmitting sensory
signals to the corresponding primary cortical area
major sensory relay station?
the thalamus
which other inputs dies the thalamus convey?
- motor inputs from the cerebellum and basal ganglia
- limbic inputs
- modulatory inputs involved in behavioral arousal and sleep–wake
cycle
What is the internal medullary lamina?
part of thalamus Divided into a medial , lateral, and anterior nuclear group by a Y-shaped white matter structure
Nuclei within the internal medullary lamina itself are
called the:
intralaminar nuclei
describe the midline thalamic nuclei
lie adjacent to the third
ventricle, several of which are continuous with and
functionally very similar to the intralaminar nuclei
what is thalamic reticular nucleus?
forms a sheet
enveloping the lateral aspect of the thalamus
WEach side of th ethalamus can be divided as? and by what is the thalamus covered?
a lateral nuclear group, a medial nuclear
group, and an anterior nuclear group by the internal medullary lamina. The thalamus is covered on its superior surface by a thin layer of white matter, called the stratum zonale, and on its lateral surface by another layer, the external medullary lamina
where are smaller nuclear groups situated?
within the internal medullary lamina, and on the medial and lateral surfaces of the thalamus.
explain the anterior neuroanatomical subdivision of the thalamus
The anterior part of the thalamus contains the
anterior thalamic nuclei.
They receive the mammillothalamic tract
from the mammillary nuclei. This is part of an important circuit called the Papez Circuit (functions primarily in the cortical control of emotion and memory storage and contains centers that regulate aversion and gratification).
These anterior thalamic nuclei also receive
reciprocal connections with the cingulate
gyrus and hypothalamus.
The function of the anterior thalamic nuclei is
closely associated with that of the limbic
system and is concerned with emotional
tone and the mechanisms of recent memory.
explain the medial neuroanatomical division of the thalamus
- The medial part of the thalamus contains
the large dorsomedial nucleus and smaller
nuclei (centromedian and ventral
posteromedial). - The dorsomedial nucleus has afferent and
efferent connections with the nuclei of the
hypothalamus, as well as with the prefrontal
cortex. The dorsomedial nucleus is the main relay center for information traveling to the frontal lobe’s prefrontal cortex. - The medial part of the thalamus is
interconnected with all other groups of
thalamic nuclei. - The medial part of the thalamus is
responsible for the integration of a large
variety of sensory information, and the
relation of the information to one’s
emotional feelings and subjective state.
Habenular nuclei-These lie on the medial surface of the dorsal medial nucleus of the thalamus. The lateral HN has been hypothesized to play a role during aversive learning.
Paraventricular thalamic nucleus- This is one of the midline thalamic nuclei and lies in the most medial aspect of the thalamus. It regulates arousal, as well as emotional and motivated behaviors
the lateral subdivison is divided inti:
dorsal and ventral tier
explain the contents of th edorsal tier of the latwral subdivision
- Lateral dorsal nucleus- processes somatosensory
information - Lateral posterior nucleus- determining visual saliency,
visually guided behaviors - Pulvinar nucleus- visual information processing,
integrating visual and motor signals
These nuclei are known to have interconnections with
other thalamic nuclei and with the parietal lobe,
cingulate gyrus, and occipital and temporal lobes
desfribe the intralaminar nuclei
located within the internal medullary lamina.
They receive input from the reticular formation, spinothalamic, and trigeminothalamic tracts, and send efferent output to other thalamic nuclei and the corpus striatum. These nuclei are involved in various
functions including awareness, consciousness, arousal, sleep, vigilance, cognition, sensation, and sexual processing.
explain midline nuclei
located adjacent to the third ventricle and within
the interthalamic connection, include the paraventricular, paratenial, reuniens, and rhomboid nuclei. They receive input from the reticular formation and are termed “nonspecific” due to their
widespread projections to the cortex and limbic structures. These nuclei regulate arousal, cognitive function, basal ganglia circuits, nociceptive input to the cerebral cortex, activity levels in target structures, and awareness.
explain reticular nucleus
is a thin layer of GABAergic neurons positioned
between the external medullary lamina and the posterior limb of the internal capsule. This nucleus receives input from various sources including other thalamic nuclei, the globus pallidus, reticular formation, and cerebral cortex. Additionally, it provides significant inhibition to thalamocortical neurons. It regulates thalamic activity, influencing sensory processing, arousal, cognition, movement initiation, alertness, and attention. Notably,
it lacks outgoing projections to the cerebral cortex.
explain medial geniculate body
forms part of the auditory pathway and
is a swelling on the posterior surface of the thalamus beneath
the pulvinar. Its main afferent is the inferior colliculus. Its major
efferent projection is to the primary auditory cortex on the
superior temporal convolution. This region plays a critical role in the
complex auditory processing necessary for robust speech
perception
explain geniculate body
forms part of the visual pathway,
appearing as a bulge beneath the pulvinar of the thalamus. It serves as the endpoint for most optic tract fibers. These fibers originate from the ganglion cell layer of the retina and convey visual
data. Each lateral geniculate body receives visual input from the contralateral visual field. Efferent fibers exit the lateral geniculate body to form the visual radiation, projecting to the visual cortex in
the occipital lobe. Thus, it provides a relay station for all the axons of the retinal ganglion cells subserving vision.
The thalamus is an important relay station for two sensory motor axonal loops involving the cerebellum and the basal nuclei:
(i) the cerebellar-rubro-thalamic·corticalponto-cerebellar loop
(ii) the cortical-striatal-pallidal-thalamic-cortical loop- The cortico-striatal-thalamo-cortical (CSTC) pathway is a brain circuit that controls movement, habit formation, and reward. The CSTC includes the orbitofrontal cortex (OFC), the anterior cingulate cortex (ACC), the basal ganglia, and the thalamus.
both loops are necessary for normal voluntary movement
explain the functional classification of specific thalamin nuclei
receive information (e.g. visual, acoustic, primary somatosensory, motor input) that is very specific and well-defined, and project this information to very specific, functionally discrete cortical areas. These nuclei include the ventral anterior (VA), ventral lateral (VL), ventral posterior (VP), medial geniculate and lateral geniculate nuclei.
