Lecture 31- Thalamus Flashcards
What structure separates the left and right thalami?
3rd ventricle
What is the main function of the thalamus?
to provide a relay station to the cerebral cortex
List the 4 parts of the diencephalon
- Epithalamus
- Subthalamus
- Hypothalamus
- Thalamus
List the 3 major structures that make up the epithalamus.
- Pineal Gland
- Posterior Commissure
- Habenular Nuclei
The pineal gland is considered to be part of which diencephalic structure?
epithalamus
What hormone does the pineal gland (part of the epithalmus) secrete? What is its function?
- Melatonin
- High levels at night-involved in circadian rhythm
What is the function of the posterior commissure?
- fiber tract connecting pretectal and oculomotor nuclei
- controls consensual pupillary response i.e.. light applied to one eye induces constriction of both pupils
What fibers are contained in the stria medullaris thalami?
afferent fibers from the hypothalmus and septal nuclei to the habenula (part of epithalamus)
What diecephalic structure is the habenula a part of?
epithalamus
Where does the habenula receive fibers from?
hypothalamus and septal nuclei (limbic system)
What forms the lateral border of the thalamus?
fibers of the internal capsule
What is the name for the fiber layer that divides the thalamus into 3 parts?
internal medullary lamina
What are the three compartments of the the thalamus?
Anterior, Medial and Lateral
What nucleus is contained in the anterior compartment of the thalamus?
anterior nucleus
What nucleus is contained in the medial compartment of the thalamus?
mediodorsal nucleus
What are the subdivisions of the lateral compartment of the thalamus?
dorsal tier, ventral tier, appended nuclei
List the 9 nuclei present in the lateral compartment?
- Pulvinar
- lateral dorsal (LD)
- ventral lateral (VL)
- lateral posterior (LP)
- Medial Geniculate Body (MGB)
- Lateral Geniculate Body (LGB)
- Anterior
- Ventroposterior medial (VPM)
- Ventroposterior lateral (VPL)
What is the most prominent interlaminar nuclei? What ascending spinal tract does it receive?
Centromedian Nucleus
paleospinothalamic tract
Where does the Centromedian nucleus receive fibers from and project?
- receives fibers from the neurons in the substantia gelatinosa via the paleospinothalamic tract
- sends fibers to the Cingulate Gyrus
What is the Centromedian nucleus involved in?
“suffering” aspect of pain
What are the four functional categories of nuclei in the thalamus?
- Sensory nuclei
- Motor relay nuclei
- Association nuclei
- Limbic nuclei
What type of information is sent to the Lateral geniculate body (LGB)? Where do the fibers come from and where are they sent to?
visual information
- comes from retinal ganglion cells
- sent to the primary visual cortex (BA 17) on the banks of the Calcarine Sulcus
What type of information is sent to the Medial geniculate body (MGB)? Where do the fibers come from and where do efferents project to?
- Audition
- Fibers come from the inferior colliculus and are sent to the Primary Auditory Cortex (BA 41-42)
What type of information is received by the Ventral Posterior Lateral (VPL) and Ventral Posterior Medial (VPM) Nuclei? Where is this information relayed?
- Fine touch, pressure, vibration and position
- sharp pain
- relayed to the Primary Somatosensory Cortex (BA 1-3)- Postcentral gyrus of the parietal lobe
Where does incoming information to the ventral posterior lateral (VPL) nucleus come from?
- Nucleus gracilis and cuneatus via the medial lemniscus
- Neurons in the Substania gelatinosa (lamina II) via the Neospinothalmic tract
Where does incoming information to the ventral posterior medial (VPM) come from?
- Spinal Nucleus of V (face pain)
- Primary Sensory Nucleus of V
- Parabrachial Nucleus
- Nucleus of the Tractus Solitarius
Where do VA/VL relay signals to?
the motor cortices
- Primary motor cortex (BA4)
- Premotor cortex (BA6)
Where do VA/VL receive signals from?
- Dentate nucleus (cerebellum)
- Globus Pallidus internal
- Substantia nigra pars compacta
What fiber tract does information from the basal ganglia to the Ventral anterior nucleus (VA) of the thalamus use?
Ansa lenticularis
What fiber tract does information from the basal ganglia to the Ventral lateral nucleus (VL) of the thalamus use?
Lenticular fasiculus
What fibers are contained in the Ansa lenticularis and the Lenticular fasiculus?
Fibers carrying info from the basal ganglia to the VA/VL of the thalamus
Name 3 thalamic association nuclei that receive input from the cortex.
- Lateral posterior nucleus
- Pulvinar nucleus
- Mediodorsal nucleus
Where does the input to the lateral posterior (LP) and pulvinar nucleus come from? Where do these fibers project to?
- Comes from sensory and association ares and the superior colliculus
- Projects to the Parietal, Temporal and Occipital lobes
What two thalamic nuclei relay info to the cingulate cortex and are therefore considered part of the limbic system?
Anterior Nucleus Lateral dorsal (LD) nucleus
Where does afferent input to the anterior and LD nucleus originate?
Hippocampus
Which sensory signal does NOT travel through the thalamus before reaching the cortex?
olfaction
What layer of the cortex do the neurons of the thalamus project to?
mainly layer 4 (small projections to 1 and 6)
What is the purpose of the thalamic triads?
-Produces excitation quickly followed by inhibition (control mechanism)
Which nucleus of the thalamus provides inhibition?
Reticular Nucleus
What are two mechanisms by which thalamic excitation is controlled.
- GABAergic neurons from the reticular nucleus
- Dendrodendritic triad-excitation followed by inhibition
What is the interthalamic adhesion? What is it also known as?
Massa intermedia
-structure connecting two thalami
What are the 5 parts of the internal capsule?
- Anterior limb
- Genu
- Posterior limb
- Retrolenticular limb
- Sublenticular limb
What 3 types of fibers are found within the anterior limb of the internal capsule?
- Anterior Nuc–>Cingulate gyrus
- MD –>Prefrontal Cortex
- Frontal lobe–>ipsilateral pontine nuclei
What 3 types of fibers are found in the posterior limb of the internal capsule?
- VA/VL–>motor cortices
- Corticospinal/Corticobulbar fibers
- VPM/VPL–> Somatosensory Cortex
Where is the sublenticular limbs of the internal capsule found? What types of fibers does it contain?
- found inferior to the lenticular nuclei (GP and putamen)
1. LGN–(optic radiations)–> Primary Visual Cortex
2. MGB–> primary auditory cortex