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HNNS > HNS05 Thalamus And Cerebral Cortex > Flashcards

HNS05 Thalamus And Cerebral Cortex Flashcards

1
Q

Thalamus

A
  • Large ovoid mass of gray matter —> forms major part of Diencephalon
    —> Anterior end: narrow, rounded
    —> Posterior end: expanded to form the Pulvinar
  • Situated on each side of ***Third ventricle (將Third ventricle夾係中間)
  • 2 halves of thalamus joined by ***interthalamic adhesion
  • very important RELAY station of most sensory systems
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2
Q

Topographic location of thalamus

A

Anterior: Interventricular foramen
Posterior: Pulvinar
Superior: Stratum zonale (White mater) and Stria terminalis
Inferior: Tegmentum of **midbrain
Medial: Lateral wall of **third ventricle
Lateral: Nerve fibres of ***internal capsules

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3
Q

Topological location of Thalamus

A

Dissection from lateral side has to go through Caudate nucleus and Putamens

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4
Q

Dorsal view of Diencephalon and Mesencephalon

A

兩邊Thalamus夾住中間下面Mesencephalon (見到Superior and Inferior colliculi)

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5
Q

Coronal sections for Diencephalon

A

see slides

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6
Q

***4 components of Diencephalon

A
  1. Epithalamus
    - **Pineal gland: secretes **melatonin
    - smallest region of diencephalon
  2. Thalamus
    - relays **ALL sensory input (perception of touch, pressure, temperature) to all parts of cortex
    - **    movement control
  3. Subthalamus
    - connects Subthalamic nuclei + Basal ganglia (Caudate nucleus + Putamen + Globus pallidus)
    —> control body movement and emotion control
  4. Hypothalamus
    - **release hormones to regulate **Pituitary gland
    - controls body ***temperature
    - eating and drinking behaviour
    - emotion
    - circadian rhythms + wake/sleep pattern
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7
Q

***Thalamic nuclei

A

Left/Right connected by interthalamic adhesion
Groups separated by internal / external medullary lamina

Anterior group:

  • part of ***limbic system
  • **memory and **emotion

Medial group:

  • **emotional output to **prefrontal cortex
  • awareness of emotions
  • subgroups: Medial dorsal (MD), Medial group (M), Midline nuclei

Ventral group:

  • **somesthetic output to **postcentral gyrus
  • signals from Cerebellum and Basal nuclei —> ***motor areas of cortex
  • subgroups: VA, VL, VP (VI+VPM+VPL)

Lateral group:

  • **somesthetic output to **association areas of cortex
  • contributes to ***emotional function of limbic system
  • subgroups: LD, LP

Posterior group:

  • relay of **visual signals to occipital lobe (via **lateral geniculate nucleus)
  • relay of **auditory signals to temporal lobe (via **medial geniculate nucleus)
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8
Q

Internal medullary lamina

A

Intralaminar nuclei + Centromedian nuclei

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9
Q

***Anterior, VA, VL, VP, Lateral geniculate, Medial geniculate, MD

(Receives signals FROM, Send signals TO)

A

Learning and Memory:

  1. Anterior (part of Limbic system):
    - from Mammillothalamic tract, Fornix (learning, memory) —> ***Cingulate cortex (posterior part)

Emotion:

  1. MD:
    - from Substantia nigra, Ventral pallidum, Olfactory cortex, Amygdala —> ***Prefrontal cortex

Motor:

  1. ***VA:
    - from Globus pallidus —> Prefrontal cortex (motor)
  2. ***VL:
    - from Globus pallidus —> Supplementary motor area
    - from Cerebellum —> Motor cortex

Sensory:

  1. ***VP (most important):
    - from Spinothalamic tract, Trigeminothalamic tract, Dorsal column-medial lemniscus pathway —> Somatic sensory cortex
  2. ***Lateral geniculate:
    - from Optic tract —> Primary visual cortex
  3. ***Medial geniculate:
    - from Inferior colliculi —> Primary auditory cortex
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10
Q

VP nucleus

A
  1. VPL: receives all somatosensory signals from ***upper + lower extremities (Dorsal column-medial lemniscus pathway + Spinothalamic tract)
  2. VPM: receives all somatosensory signals from ***head + neck region (Trigeminothalamic tract)

(Somatosensory signals: Mechanoreception + Proprioception + Thermoception + Nociception)

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11
Q

***Functions / Roles of Thalamus in neuro-network

A

***ALL sensory signals (from Spinothalamic tract + Dorsal-medial lemniscal pathway) has to go through thalamus, but NOT motor control

Sensation:
Example: Pain sensation:
Sensation —> Dorsal horn —> Spinothalamic tract —> Medulla, Pons, Midbrain —> **Thalamus (form synapse) —>
1. **Learning and memory cortex (avoid pain sensation in the future again)
2. ***Sensory cortex (Parietal lobe) —> Motor cortex —> Corticospinal tract —> Brainstem (Cerebral peduncle, Pyramid) —> Ventral horn

Motor control:
1. Corpus striatum, Diencephalon, Cerebellum
—> ***Thalamus
—> Cerebral cortex
—> go straight back to Corpus striatum, Diencephalon, Cerebellum

2. Brainstem, Spinal cord
—> ***Thalamus
—> Cerebral cortex
—> go straight back to Brainstem, Spinal cord
—> Muscle
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12
Q

Involvement of Thalamus in Basal Ganglion circuit

A

Thalamus: modulate eventual motor output (NOT a part of basal ganglia)

Basal ganglia: Fine tuning of motor movement (finger movement, gait)

Basal ganglia components:

  • Striatum
  • Globus pallidus
  • Subthalamic nucleus
  • Substantia nigra
Direct pathway:
Cortex —(glutamate)—>
Striatum —(more GABA)—>
Globus pallidus (internal segment) —(less GABA)—>
Thalamus (VL) —(more glutamate)—>
Supplementary motor area
Indirect pathway:
Cortex —(glutamate)—>
Striatum —(more GABA)—>
Globus pallidus (external segment) —(less GABA)—>
Subthalamic nucleus —(more glutamate)—>
Globus pallidus (internal segment) —(more GABA)—>
Thalamus (VL) —(less glutamate)—>
Supplementary motor area

***Balance between direct / indirect pathway go to Thalamus eventually
—> control motor area

Substantia nigra:

  • release dopamine (inhibitory/excitatory) —> Striatum
  • fine tuning of direct / indirect pathway

Compacta:
- also fine tuning of direct / indirect pathway

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13
Q

Cerebral cortex / Telencephalon

A

凸起: Gyrus
中間d隙: Sulcus

Components:

  1. Frontal lobe (***motor control + emotion, also receives input from thalamus to tell how good motor control is)
  2. Parietal lobe (ultimate analysis of ALL ***sensory signals from thalamus)
  3. Occipital lobe (***vision centre —> primary visual cortex)
  4. Temporal lobe (**learning, **memory, emotion)

Central sulcus: separate frontal / parietal lobe
—> gyrus in front (Precentral gyrus): Primary motor cortex
—> gyrus behind (Postcentral gyrus): Primary somatosensory cortex

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14
Q

Frontal lobe

A
  1. Primary motor cortex (Area 4)
  2. Motor association area (Area 6: Premotor area + SMA)
  3. Pre-frontal cortex
  4. ***Broca’s area (language area)
    (5. Olfactory association area)
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15
Q

Occipital lobe

A
  1. Primary visual cortex

2. Visual association area

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16
Q

Temporal lobe

A
  1. Primary auditory cortex
  2. Auditory association area
  3. Primary olfactory cortex
17
Q

Parietal lobe

A
  1. Primary somatosensory cortex
  2. Somatosensory association area
  3. Primary gustatory cortex (taste)
  4. ***Wernicke’s area (comprehension of language)
18
Q

Grey matter

A

Collection of Cell bodies

  1. Insula (physio, psychological pain, olfactory sensation) (enclosed within other gyrus)
  2. Caudate nucleus + Putamen —> Striatum
  3. Basal ganglia (Globus pallidus, Substantia nigra)
19
Q

Broca’s area + Wernicke’s area

A

joined by ***Arcuate Fasciculus (several axons grouped together)
—> from Wernicke’s area (Parietal lobe) to Broca’s area (Frontal lobe)

20
Q

Fibres of white matter of Cerebrum

A
  1. Arcuate fibres (最短)
    - interconnect gyri within a lobe
  2. Association fibres
    - interconnect cortical areas within same hemisphere / linking several gyri together
  3. Longitudinal fasciculi (前後)
    - interconnect frontal lobe with other cerebral lobes
  4. Corona radiata (上下)
21
Q

6 layers of cortex

A
  1. Molecular layer
  2. External granular layer
  3. External pyramidal layer
  4. Internal granular layer
  5. Internal pyramidal layer
  6. Multiform layer

Differ in distribution of neurons

22
Q

Different staining methods

A
  1. Golgi stain: cell bodies + axons
  2. Nissl stain: cell bodies only
  3. Weigert stain: axons only
23
Q

Corpus callosum

A

Connect left + right hemisphere

24
Q

Learning and memory

A
  1. Limbic system
  2. Basal nucleus of Meynert
  3. Septal nucleus (headquarter of cholinergic neuron to pre-frontal cortex)
25
Q

***Limbic system

A

Learning + Memory + Emotion

Diencephalon components:

  1. ***Anterior group of thalamic nuclei
  2. ***Hypothalamus
  3. Mamillary body

Cerebrum components:

  1. ***Cingulate gyrus
  2. ***Hippocampal formation (Hippocampus + Dentate gyrus + Subicular complex)
  3. Parahippocampal gyrus
  4. Entorhinal cortex

Other components:

  1. Fornix + Fimbria
  2. ***Amygdala (negative emotion)
26
Q

***Learning loop (Papez circuit)

A

Repeated stimulation of Hippocampus:

Cingulate gyrus
—> Parahippocampal gyrus
—> Entorhinal cortex
—> Hippocampus (Dentate gyrus)
—> Fimbria
—> Fornix
—> Mamillary body (of Hypothalamus)
—> Mammillothalamic tract
—> ***Anterior nucleus of Thalamus
—> Cingulate gyrus (posterior)
—> Parahippocampal gyrus
—> Hippocampus

(—> Cingulate gyrus (anterior) —> Basal nuclei —> Occipitofrontal nucleus —> Subcallosal area of cortex)

27
Q

Amygdaloid complex

A

Amygdala + Stria terminalis

Anterior to Hippocampus

Functions:

  1. Involve in defence and attack, fear, rage (***negative emotions)
  2. Influence ***endocrine function of hypothalamus
28
Q

Hippocampal formation

A 
Entorhinal cortex (within Parahippocampus gyrus)
—> sends signals to Dentate gyrus (within Hippocampus)

Functions:

  1. ***Learning, recent memory
  2. ***Emotion
29
Q

***Summary of memory

A

Long term memory

  • Explicit memory (declarative): **Hippocampus, **Nucleus Basalis, Medial temporal lobe
    —> Remembering events (episodic memory)
    —> Remembering facts (semantic memory)
  • Implicit memory (non-declarative)
    —> Skills and habits: **Striatum, Motor areas of cortex, Cerebellum (muscle memory)
    —> Emotional associations: **    Amygdala, Insula
    —> Conditioned reflex: ***Cerebellum

Working memory: ***Prefrontal cortex (PFC)
—> Non-spatial (colour, shape): Ventrolateral PFC
—> Spatial memory: Dorsolateral PFC

30
Q

Clinical relevance of cerebral cortex

A
  1. Alzheimer’s disease
    - shrinkage / atrophy of whole brain, enlarged lateral ventricle
    - start with Hippocampus —> temporal lobe: affect memory, language
  2. Frontotemporal lobe dementia
    - atrophy of frontal lobe
  3. Creutzfeldt-Jakob disease
    - prion change brain protein to beta-sheet —> neuron die
    - vacuoles / holes formed in the cortex
    - affect mental acuity + memory (limbic system)

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