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18 Cards in this Set

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Describe the thalamus and lists its 3 borders?
The thalamus forms the bulk of the diencephalon, which can be thought of as the most rostral extension of the brainstem. Sometimes referred to as the “gateway to the cerebrum”. The thalamus receives and integrates important afferent projections from all of the major subcortical sensory nuclei, the cerebellum, the basal ganglia, and parts of the limbic system. Its major efferent projections are the cerebral cortex, from which it also receives extensive reciprocal connections.

BORDERS:

The thalamus (literally “inner chamber”) appears as a mass of gray matter deep within the cerebrum. Its borders include the:

A. Third ventricle (medial)
B. Internal capsule (lateral)
C. Lateral ventricle and fornix (superior)
What is the internal medullary lamina?
On cut surface, the gray matter of the thalamus is traversed by a number of myelin-rich (i.e. white matter) fiber tracts, including the internal medullary laminas, which divide it into various nuclear groups. A thin Y-shaped sheet of myelinated fibers, the internal medullary lamina, delimits the anterior, medial, and lateral groups of nuclei of the thalamus.
What is the external medullary lamina and how is it related to the reticular nucleus of the thalamus?
The lateral groups of nuclei are covered by the external medullary lamina, another sheet of myelinated fibers. Interposed between those fibers and the internal capsule is a thin group of neurons forming the reticular nucleus of the thalamus
1. Level of consciousness
changes as a function of what?

2. The focus of consciousness changes as a function of what?

3. The form Of consciousness changes as a function of what?
1. Level of consciousness
changes as a function of activation.

2. The focus of consciousness changes as a function of input/output.

3. The form Of consciousness changes as a function of modulatory neurotransmitter ratio.
Describe the 3 Functional Categorization of the Thalamic Nuclei?
1. Specific (relay) Nuclei: relay stations in pathways conducting specific sensory or motor information to specific cortical areas.

2. Association Nuclei: reciprocal connection with association area of the cerebral cortex and receive projection from other thalamic Nuclei

3. Subcortical nuclei (diffuse projection): do not have reciprocal connections with the cerebral cortex


NOTES:

Thalamic nuclei can also be classified into several groups based on the pattern and information content of their connections (Table I). For Example Specific relay nuclei project to and receive input from specific regions of cerebral cortex. Those reciprocal connections apparently allow the cerebral cortex to modulate the thalamic input it receives. Specific relay nuclei process input either from a single sensory modality or from distinct parts of the motor system. For example the lateral geniculate receives visual input from the optic tract and projects to the primary visual area of the occipital cortex. The association relay nuclei receive highly processed input from more than one source and project to larger area of the association cortex. For example the medial dorsal thalamic nucleus receives input from the hypothalamus and amygdala and is reciprocally interconnected with prefrontal cortex and certain premotor a temporal cortical regions. In contrast to relay nuclei, diffuse-projection nuclei receive input from diverse sources and project to widespread areas of cerebral cortex and to the thalamus. Finally, the reticular nucleus is somewhat unique in that it receives input from collaterals of the axons that reciprocally connect to other thalamic nuclei and cerebral cortex.
What are the 2 types of synaptic receptors used by the thalamus?
1. Ionotropic receptor: The binding causes a conformational change that opens the ion channel which forms the central core of the receptor complex.

2. Metabotropic receptor: The conformation change in the receptor ends in activation of G-protein,which intern leads to a cascade of biochemical reactions in the membrane and cytoplasm of relay cells.
Name 6 neurotransmitters in the thalamus?
1. Glutamate
2. GABA (y-aminobutyric acid)
3. Acetylcholine
4. Noradreneline
5. Serotonin
6. histamine
Girl's Got yANSH
Describe thalamocortical axons?
local cortical lesions produce thalamic degenerative changes.
Describe the thalamic reticular nucleus?
A thin neuronal shell which surrounds the lateral, superior and rostroinferior aspect of the dorsal thalamus. It projects to
principal thalamic nuclei, not the cortex, and receives input from the MD. It serves as “gate” activity of the thalamus.
1. What are the 6 Specific (relay) Nuclei?

2. What are the 4 association nuclei?

3. What is the 1 subcortical nuclei with diffuse projection?
SEE CHART
1.
2. Asshole = Late and LiMP
Name 5 major functions of the thalamus?
1. Sensory integration and relay:- All forms of sensory input (except olfactory).

2. Motor integration and relay:- the corpus striatum, SN and cerebellum exert their influence on corticospinal and corticobulbar motor pathway via the thalamus.

3. Awareness of nociceptive stimuli:- occur in non-discriminative form at thalamic level.

4. Emotional and subjective responses to sensation:- connections with prefrontal cortex influence mood and personality.

5. Memory and instinctive behavior:-
Torture = MASE Men!
What are the functions of these nuclei of the thalamus:

1. Anterior
2. Medial dorsal
3. Pulvinar
4. Ventral anterior
5. Ventral lateral
6. Ventral posterior
7. Lateral geniculate
8. Medial geniculate
9. Centromedian
see table
Describe thalamic syndrome?
Patients who sustain injury to the ventral posterior regions of the thalamus may develop thalamic syndrome, characterized by impairment of proprioception, touch, pain, and temperature on the contralateral side of the body.
Describe suprathalamic syndrome?
Lesions above the thalamus leading to loss of cortical sensory functions contralateral to the lesion.
Lesions in the medical dorsal thalamic nucleus have been associated with what?
Lesions in the medical dorsal thalamic nucleus have been associated with Korsakoff’s
syndrome, an interesting constellation that includes an inability to form new memories, problems with retrieving old memories, and a bizarre “fabrication” of memories, termed confabulation. Chronic alcoholism could cause this.
MDs Kill and fabricate
Degeneration of anterior thalamic nuclei is associated with what?
The central role played by the thalamus in cognition and arousal is dramatically illustrated in patients with an unusual disease termed fatal familial insomnia, a prion-associated disorder characterized by degeneration of the anterior thalamic nuclei.
Neuronal losses in the anterior and dorsal medial nucleus have been associated with what?
Recently, neuronal losses in the anterior and dorsal medial nucleus have been associated with neuropsychiatric disorders (such as Alzheimer’s disease and schizophrenia).
1. What is Narcolepsy?

2. What is cataplexy?
1. Narcolepsy is a neurological condition characterized by severe fatigue, irresistible episodes of sleep and general sleep disorder. The main characteristic of narcolepsy is overwhelming excessive daytime sleepiness (EDS), even after adequate nighttime sleep. A person with narcolepsy is likely to become drowsy or to fall asleep, often at inappropriate times and places.

2. Cataplexy: A debilitating medical condition in which a person suddenly feels weak and collapses at moments of strong emotion such as laughter, anger, fear or surprise. In so collapsing, people with cataplexy may injure themselves. There are high levels of hypocretin or orexin in the lateral thalamus so this is a neuropeptide disorder.