Lecture 16: Thalamus Flashcards Preview

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Flashcards in Lecture 16: Thalamus Deck (20):
1

Dorsal thalamus (development)

Multiple nuclei that connect bidirectionally with cortex; ends up making up the majority of the thalamus

2

Ventral thalamus (development)

(Reticular nucleus) Connects bidirectionally with dorsal thalamus

3

What fiber divides the thalamus? What groups of nuclei? (3 + 1)

Internal medullary lamina (y shaped); anterior, medial, lateral (and intralaminar)

4

Back end of thalamus is...

Sensory

5

Front end of thalamus is...

Motor

6

Describe ventral thalamus

Sheet of purely GABAergic inhibitory neurons; surrounds anterior, lateral, ventral surfaces of dorsal thalamus; sends axons ONLY to dorsal thalamus

7

What type of neuron is the GABA neuron w/in a dorsal thalamic nucleus.

Interneuron (inhibitory)

8

Ascending thalamic input synapses where? Effect? Name?

On relay neuron AND GABA neuron (relay gets it first); delayed inhibition via GABA; Feedforward inhibition

9

Where does the relay neuron project? Then what?

Input to level IV of the cortex; return projection to the thalamus from level VI

10

Where else does the relay neuron project?

TRN to GABAergic neuron, which projects back to relay (feedback inhibition)

11

Where else do the return projections to the thalamus synapse?

TRN to GABAergic neuron, which projects back to relay (feedforward inhibition)

12

Describe thalamic/cortical EEG

Ensembles of thalamic and cortical neurons discharge synchronously at stereotyped frequencies associated with different conscious states (alert, drowsy, sleep)

13

Awake/alert = what mode and function?

Tonic firing (depolarized), allows information transfer to cortex

14

Drowsy/deep sleep = what mode and function? What wave?

Burst firing (hyperpolarized, so you get a "burst" of APs), blocks transfer to cortex; delta wave

15

How do we get from hyperpolarized to depolarized modes?

Turned on by ACh, 5HT, NA (project to dorsal thalamic nucleus), and histamine (note: histamine also projects TRN)

16

Lesions: Thalamic syndrome

Damage to posterior thalamus (usually vascular, including VPL/VPM); contralateral hemianesthesia with excruciating “central” pain

17

Lesions: Tremor states

Rhythmic bursts in VA/VLa in PD due to frequency abnormalities in pallidothalamic circuits

18

Lesions: Amnesia

Lesions of the anterior and MD nuclei

19

Lesions: Absence seizures

Spike and wave patterns entrained by very long bursts in GABAergic neurons of the TRN

20

Thalamocortical and corticothalamic connections are ipsi/contralateral & inhib/excitatory

Ipsilateral; excitatory

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