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ANAT 321 > Thalamus > Flashcards

Thalamus Flashcards

1
Q

Convergence

A

Neuron in brainstem is receiving sensory input from e.g skin, the neuron is getting input from many sensory neurons, they are all converging on this neuron
Neuron is getting complex input

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2
Q

Divergence

A

One sensory neuron is sending an axon that splits and communicates with multiple neurons. Multiple 2nd order neurons are innervated by one sensory neuron
Seems like we are losing precision

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3
Q

Retina example of divergence

A

Millions of pixels coming up from retina, as we move up through visual pathway info gets combined
Lines make shapes, shapes make more complex shapes

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4
Q

Explain Lateral Inhibition

A

Strong central signal passes through and filters out weak surrounding signals
Inhibits neurons that are lateral to middle neuron
Inhibitory interneurons release GABA on side neurons so they are inhibited so center neuron fires a lot of AP but lateral neurons don’t fire
Lateral inhibition is found everywhere in sensory systems

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5
Q

2 types of neurons in the brain

A

Excitatory - Glutamate
Inhibitory - GABA

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6
Q

GABA vs Glutamate axon length

A

Glutamate - long
GABA - short, localized

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7
Q

Gateway to cerebral cortex almost always…

A

Thalamus

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8
Q

3 planes of cutting brain

A

Coronal
Horizontal
Sagittal

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9
Q

Thalamus

A

Organized as numerous discrete nuclei

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10
Q

3 functional distinct groups of thalamic nuclei

A

specific relay
association
intralaminar

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11
Q

Specific relay nuclei

A

Converge in VPL and VPM (ventral posterior lateral/medial)

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12
Q

VPL

A

SomatoSensory from body

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13
Q

VPM

A

Somatoensory info from head

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14
Q

Where in thalamus do specific relay nuclei convey visual information?

A

Lateral Geniculate Nucleus

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15
Q

Where in thalamus do specific relay nuclei convey auditory information?

A

Medial Geniculate Nucleus

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16
Q

Regions that control movement

A

Cerebellum
Basal ganglia

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17
Q

Ventral anterior and ventral lateral nuclei

A

Specific relay nuclei that connect the cerebellum and basal ganglia with the motor cortex

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17
Q

2 main association nuclei

A

Medial Dorsal Nucleus
Pulvinar Nucleus

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18
Q

How do we ignore everything that we see except what we focus on?

A

Blocking some stuff

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19
Q

What might association nuclei be doing?

A

Gatin info flow between different regions of the cerebral cortex (thalamus can act as a gate)
POSSIBLE NOT FOR SURE

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20
Q

Medial Dorsal Nucleus (MD)

A

Inputs: Prefrontal cortex, olfactory and limbic structures
Cortical outputs: Prefrontal cortex

20
Q

Pulvinar Nucleus

A

Inputs: Parietal, Occipital and temporal lobes
Outputs: Parietal, occipital and temporal lobes, superior colliculus

21
Q

Intralaminar Nuclei

A

Internal medullary lamina has clusters of neurons embedded in it, probably part of the arousal system but this is hypothesized
Project diffusely to many region so cortex as well as subcortical structures such as basal ganglia

22
Q

What’s up with that stray neural synapse in the brainstem on the anterolateral pathway?

A

Activates the arousal system. That’s why pain causes arousal.

23
Q

MEMORIZE SPCIFIC RELAY NUCLEI OF THALAMUS TABLE

A

GO TO SLIDE NAMED SPECIFIC RELAY NUCLEI OF THE THALAMUS

24
Q

Pulvinar

A

Posterior/Caudal (Back parts of brain)

25
Q

Medial Dorsal

A

Medial Dorsal

26
Q
A

Every single thalamic nucleus is getting input from the cerebral cortex

27
Q

Feedforward projections

A

Projections going UP the pathway
E.g brainstem to VPL nucleus

28
Q

Feedback projections

A

Projections going down to thalamus

29
Q

Feedforward and feedback vision example

A

Retina -> LGN -> Cerebral cortex = feedforward
Cerebral cortex -> LGN = feedback

30
Q

Cerebral Cortex

A

Thin sheet of tissue 2-4mm
Divided into 6 layers
1 - outermost
6 - deepest

31
Q

Where do feedforward projections from the relay nuclei project?

A

Layer 4

32
Q

Example of C.C layer projections

A

Optic tract, Brainstem and Thalamic reticular Nucleus (GABA) feedforwarding to the Lateral Geniculate which then feedforwards to Layer 4 which then shows a feedback signal going back to the Lateral Geniculate from LAYER 6

33
Q

Driver inputs

A

Come from retina

33
Q

Modulator inputs

A

Feedback inputs coming from Layer 6 of cortex going back to Lateral Geniculate
Come from brainstem (NE neurons) - tweak and modulate basic physiologic properties of the thalamic neurons
Neuromodulators modulate behavioral of thalamus
Thalamic reticular nucleus (GABA) projects into thalamus and modulate

34
Q

For Association nuclei…

A

Driver inputs are coming from the cerebral cortex AND modulator inputs are coming from the cerebral cortex
Driver inputs come from layer 5
Modulator come from layer 6

35
Q

Feedback projections to the thalamus come from which Layer of CC?

A

Layer 6

36
Q

Hypothesis for what thalamus is doing - gatekeeper regulating info flow to the cortex

A

Modulatory inputs could be playing a role in altering the physiological properties with specific thalamic neurons so that the different neurons are either relaying the info to the cortex in different ways or maybe some of the neurons are relaying the info up and other neurons the info is getting filtered out
Maybe helps you pay attention

37
Q

AP firing methods for thalamic neurons

A

Transmission mode
Bursting Mode

38
Q

Transmission Mode

A

Output mirrors input
If sensory inputs increase their firing rates then thalamic neurons will increase their firing rates

39
Q

Bursting Mode

A

Fire bursts of 3-8 action potentials separated by quiet periods lasting 100s of milliseconds
Sleep wave cycles

40
Q

2 diff firing modes of thalamic neurons

A

Bursting
Transmission

41
Q

Bursting mode and Sleep wave cycles

A

Neurons in cerebral cortex start firing in rhythmic bursts similarly to thalamic neurons
Complicated interaction between C.Cortex and thalamus

42
Q

How are thalamic neurons shifted from burst firing mode to tonic (transmission) firing mode?

A

Neuromodulators (Acetylcholine, NE and Histamine) which are released during wakefulness depolarize thalamic neurons

43
Q

Reading 3

A

Association Nuclei of the Thalamus

44
Q

Internal Capsule

A

Axons follow the internal capsule which is a massive fiber tract to get to and from the cerebral cortex

45
Q

Where is the internal capsule?

A

Thin sheet of white matter surrounding the thalamus

46
Q

Horizontal view of internal capsule vs Coronal view

A

Look at slides

47
Q
A

ANAT 321 (17 decks)

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