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Med Neuro Block 4 > 1 - Diencephalon Structure and Function > Flashcards

1 - Diencephalon Structure and Function Flashcards

1
Q

Where is the diencephalon located?

A

Embryologically between the telencephalon and mesencephalon.

Between the cerebral cortex and brainstem, medial to the internal capsule, divided in the midline by the 3rd ventricle.

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2
Q

What are the 5 subdivisions of the diencephalon?

A
  1. Epithalamus
  2. Dorsal thalamus or thalamus
  3. Ventral thalamus
  4. Subthalamus
  5. Hypothalamus
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3
Q

What makes up the epithalamus and what is its function?

A

Habenular nuclear complex, pineal gland, and posterior commisure.

Habenula: involved in limbic pathway

Pnieal gland: synthesizes serotonin and converts it to melatonin

Posterior commisure: lings pretectal and other nuclei of the two sides

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4
Q

What are the components of the dorsal thalamus or thalamus and what is the function of each?

A

Thalamic nuclei: provide strong link to the cerebral cortex.

External medullary lamina: narrow band of myelinated fibers lateral to thalamic nuclei

Internal medullary lamina: band of myelinated fibers that subdivide thalamic nuclei into anterior, lateral, and medial nuclear groups.

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5
Q

What are the components of the ventral thalamus and what is the function of each?

A

Reticular nucleus of the thalamis: between the external medullar lamina and the internal capsule

Ventral lateral geniculate nucleus (vLGN)

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6
Q

Where is the subthalamus located?

A

Between the hypothalamus and the dorsal thalamus

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7
Q

What are the components of the subthalamus and their function?

A

Zona incerta: rostral extension of the brainstem reticular formation

Subthalamic nucleus (of Luys)

Involved with basal ganglia and extrapyramidal activity.

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8
Q

What is the funciton of the hypothalamus?

A

Controlling center of the autonomic nervous system.

It has neurobehavioral functions and regulates hormones released by the hypophysis.

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9
Q

What are the components of the hypothalamus?

A

Hypothalamuc nuclei

Infundibulum

Hypophysis (pituitary gland)

Hypophyseal portal system: vascular connection between the hypothalamus and the anterior pituitary

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10
Q

What is the blood supper to the thalamus?

A

Branches of:

  • Anterior communicating artery
  • Posterior communicating artery
  • Anterior cerebral artery (ACA)
  • Posterior cerebral artery (PCA)
  • Internal carotid artery
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11
Q

What is the location of the dorsal thalamus proper or simply the thalamus?

A

Medial to the posterior limb of the internal capsule

Surrounds the third ventricle

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12
Q

What is the embryonic derivation of the thalamus?

A

Part of the diencephalon

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13
Q

What are the major functions of the thalamus?

A

“Gateway to cortex:

  1. Relays all sensory info to cortex (olfactory input to thalamus is from the piriform cortex)
  2. Relays info about motor activities to cortex
  3. Integrates sensory info from different modalities and projects to associated cortex
  4. Relays emotional and affective info to cortex
  5. Part of “papex circuit” of Limbic systen and projects to limbic cortex
  6. Intimately invovled in control of alertness, arousal, and sleep
  7. Uner direct cortical feedback and control: receiprocal connections between thalamus and cortex
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14
Q

The subdivisions of the thalamus are delineated by what? What are the major subdivisions?

A

By internal and external medullary laminae.

  1. Anterior nuclear group
  2. Lateral-ventral tier
  3. Lateral-dorsal tier
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15
Q

What is the afferent input, the efferent output, and functions of the anterior nuclear group of the thalamus?

A

Afferent input: mammillary body

Efferent output: Cingulate gyrus

Functions: Limbic

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16
Q

What is the afferent input, the efferent output, and functions of the Ventral anterior (VA) and Venteral lateral (VL) subdivisons of the Lateral Ventral tier of the thalamus?

A

Ventral anterior (VA)

  • Afferent: globus pallidus
  • Efferent: premotor cortex (6)
  • Function: motor

Venteral lateral (VL)

  • Afferent: dentate nucleus
  • Efferent: Motor and premotor (4 and 6)
  • Function: Motor
17
Q

What is the afferent input, the efferent output, and functions of the Ventral posterior lateral (VPL) and Ventral posterior medial (VPM) subdivisons of the Lateral Ventral tier of the thalamus?

A

Ventral posterior lateral (VPL)

  • Afferent: DC/ML and spinothalammic
  • Efferent: Somatosensory cortex (3, 2, 1)
  • function: somatic sensation (body)

Ventral posterior medial (VPM)

  • Afferent: Sensory nuclei of trigeminal nerve
  • Efferent: somatosensory cortex (3 ,2, 1)
  • Function: somatic sensation (face)
18
Q

What is the afferent input, the efferent output, and functions of the Lateral geniculate (LGN) and Medial geniculate (MGN) subdivisons of the Lateral Ventral tier of the thalamus?

A

Lateral geniculate (LGN)

  • Afferent: Retinal ganglion cells
  • Efferent: primary visual cortex (17)
  • Function: vision

Medial geniculate (MGN)

  • Afferent: Inferior colliculus
  • Efferent: Primary auditory cortex (41, 42)
  • Function: Audition
19
Q

What is the afferent input, the efferent output, and functions of the Lateral Dorsal (LD) and Lateral Posterior (LP) subdivisons of the Lateral Dorsal tier of the thalamus?

A

Lateral Dorsal (LD)

  • Afferent: cingulate gyrus
  • Efferent: Cingulate gyrus
  • Function: emotional expression

Lateral Posterior (LP)

  • Afferent: Parietal cortex
  • Efferent: Parietal cortex
  • Function: Sensory integration
20
Q

What is the afferent input, the efferent output, and function of the Pulvinar (Pul) subdivison of the Lateral Dorsal tier of the thalamus?

A

Pulvinar (Pul)

  • Afferent: Superior colliculus, parietal, occipital, and temporal lobes
  • Efferent: parietal, occipital, and temporal lobes (POT)
  • Functions: Ingetration of sensory info
21
Q

What is the afferent input, the efferent output, and function of the Medial Dorsal (MD) subdivison of the Medial group of the thalamus?

A

Medial Dorsal (MD)

  • Afferent: Amygdaloid nuclear complex, olfactory, and hypothalamus
  • Efferent: prefrontal cortex
  • Functions: limbic
22
Q

What are the afferent inputs, the efferent outputs, and the functions of the midline nuclei?

A

It’s a diffuse-projection nuclei.

Afferent: Reticular formation and hypothalamus

Efferent: Basal forebrain

Function: limbic

23
Q

WWhat are the three subdivisions of the intralaminar nuclei of the thalamus? What type of nuclei are these?

A

These are diffuse-projection nuclei

Centro-median (CM)

Centro-lateral (CL)

Parafascicularis (PF)

24
Q

What are the afferent inputs, the efferent outputs, and the functions of the Centro-medial (CM), Centro-lateral (CL), and Parafascicularis (PF) subdivisions of the intralaminar diffuse-projection nuclei?

A

Afferent: reticular formation, spinothalamus tract, globus pallidus, and cortical areas.

Efferent: basal ganglia and wide areas of the cortex

Function: role in pain, sleep, and wakefulness

25
Q

What are the afferent inputs, the efferent outputs, and the functions of the reticular nucleus?

A

This is a diffuse-projection nucleus

Afferent: cortex, thalamus, and brainstem reticular formation

Efferent: Thalamic nuclei

-Function: modulation of thalamic activity

26
Q

What is the thalamic neuronal circuit?

A

Afferent input projects to thalamic interneuons and to thalamic relay neurons.

Thalamic relay neurons project to the cerebral cortex, which projects back to the thalamic relay neurons.

27
Q

What is the sinlge cell response from the VPL of human during therapeutic surgery?

A

Bursts of discharge in specific sensory relay nucleus of the VPL when a speficic sensory periphery on the contralateral body is stimulated.

28
Q

How common is thalamic syndrome and what can it be caused by?

A

Relatively rare.

Usually caused by a vascular lesion or tumor and involves damage to the lateral group of thalamic nuclei (VPL).

29
Q

What are symptoms of thalamic syndrome?

A

Initially: transient CONTRA hemianalgesia

Soon: painful sensations appear with noxious stimuli

Later: pain is provoked by pressure, touch, and vibration.

In time, state of spontaneous, constant or paroxysomal pain is evoked on the affected side (contralateral to the lesion) without an external stimulus - called Dysesthesia

30
Q

With thalamic syndrome, describe the threshold for pain, temp, and tactile sensation on the affected side (contra to the lesion)?

A

The threshold for pain, temp, and tactile sensation is usually raised.

But, once the threshold is reached, pain has a strong emotional overtone to it.

31
Q

What activates the non-specific Reticular Activating System (RAS)? What is it interconnected with?

A

Repetitive, low-frequency stimulation.

Interconnected with each other and reciprocally with specific thalamic nuclei.

32
Q

What occurs with repetitive stimulation of the non-specific Reticular Activating System (RAS)? What is its function?

A

Repetitive stimulation of the non-specific thalamuc nuclei evokes cortical recruitment responses that waxes and wanes.

Controls the level of excitability of neurons over wide areas of cortex.

Med Neuro Block 4 (10 decks)

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