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Neuroanatomy > 5. Rhinencephalon & the limbic system > Flashcards

5. Rhinencephalon & the limbic system Flashcards

1
Q

2 functional divisions of the rhinencephalon

A
  1. Olfactory (paleopallium)
  2. Limbic (archipallium)
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2
Q

Components of the paleopallium - olfactory rhinencephalon (image slide 8-9)

A
  • OLFACTORY BULB (source of olfactory neurons)
  • OLFACTORY PEDUNCLE (has 2 olfactory tracts)
  • PIRIFORM LOBE (with its lateral olfactory gyrus + parahippocampal gyrus)
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3
Q

Components of the limbic system (archipallium) - limbic rhinencephalon

A

TELENcephalon
* Hippocampus
* Cingulate gyrus
* Septal area

DIencephalon
* Hypothalamus
* Thalamus
* Epithalamus

MESencephalon
* Intercrural nucleus
* Reticular formation

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4
Q

3 histological divisions of the Rhinencephalon

A
  • Molecular layer (I)
  • Pyramidal layer (V)
  • Multiform (VI)
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5
Q

3 roles of the olfactory rhinencephalon

A
  1. Localize FOOD
  2. Reflex secretion of DIGESTIVE ENZYMES
  3. Detect DANGER
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6
Q

What means ‘Macro- vs microsmatic’ species

A
  • MACROsmatic: highly developed olfactory rhinencephalon -> dogs, bears, opossums
  • MICROsmatic: poorly developed olfactory rhinencephalon -> primates
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7
Q

OLFACTORY NEURONS
1. Cell type?
2. Location (cell body + dendrites) ?

(slide 10)

A
  1. Bipolar
  2. Olfactory epithelium`

N.b. dendritic bulbs have little CILIA that project in the mucosal end of the epithelium in the nasal cavity

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8
Q

OLFACTORY NEURON - mechanism of signal trasduction by odorants?

A
  1. Odorant binds GPCR
  2. Activates adenylate cyclase
  3. Converts ATP -> cAMP
  4. cAMP activates Na channel
  5. Depolarization -> AP
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9
Q

2 rules broken by olfactory neurons

A
  1. Regenerate (replaced after 1 month)
  2. cell body elsewhere than DRG or CN ganglion
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10
Q

Are olfactory neurons myelinated?

A

No

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11
Q

In the olfactory bulb, olfactory neurons synapse with which cell types? (slide 10)

A

Brush and mitral cells (in the glomeruli of olfactory bulb)

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12
Q

Role of the olfactory peduncle

A

Contains axons (of the brush and mitral cells) connecting olfactory bulb with piriform lobe + limbic system. Axons are grouped into 2 olfactory tracts (lateral and medial)

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13
Q

Two targets of the LATERAL olfactory tract (slide 16)

A
  1. to olfactory TUBERCLE (nucleus between lateral and medial tracts) -> to PIRIFORM LOBE
  2. to LIMBIC SYSTEM (amygdala, entorhinal cortex, parahippocampal gyrus, hippocampus)
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14
Q

Two targets of the MEDIAL olfactory tract (slide 16)

A
  1. to CONTRALATERAL OLFACTORY BULB via rostral commissure
  2. to LIMBIC SYSTEM (septal nuclei -> medial forebrain bundle-> hypothalamus or reticular formation -> pS nuclei of CNVII, IX, X -> stimulate salivation + gastric secretions)
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15
Q

3 neurons of the olfactory pathways

A
  1. Olfactory neuron
  2. Olfactory bulb
  3. Variable depending on tract (lateral vs medial)
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16
Q

Describe the olfactory pathway

A
  • OLFACTORY NEURON in olfactory epithelium (neuron 1)
  • Joins other olfactory axons to form OLFACTORY NERVE (CNI)
  • crosses cribriform plate
  • Synapse with brush and mitral cells of the OLFACTORY BULB (neuron 2) just on top of cribriform plate
  • Axons project caudally to form the OLFACTORY TRACTS of the olfactory peduncle

SUMMARY:
- Olfactory epithelium
- Olfactory neuron (CNI)
- Olfactory bulb
- Olfactory tracts (peduncle)
- Lateral tract = to olfactory tubercle -> piriform lobe OR limbic system
- Medial tract = to contralateral olfactory bulb OR limbic system

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17
Q

Do olfactory pathways have a thalamic relay?

A

No (thalamus evolved after)

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18
Q

Term for loss of smell

A

Anosmia

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19
Q

Effect of a lesion to
1. one olfactory bulb
2. two olfactory bulbs
3. Limbic sytem

A
  1. Unilateral anosmia
  2. Complete anosmia
  3. No effect on smell (but effect on emotional responses)
20
Q

Most common causes of anosmia

A
  • Severe rhinitis
  • Head trauma
  • Distemper
  • Metronidazole
21
Q

What are the constituents of the two cortical rings at the diencephalon-telencephalon junction (slide 23)

A

INNER RING:
- Amygdala
- Hippocampus

OUTER RING
- Cingulate gyrus
- Septal area

22
Q

AMYGDALOID BODY
- Location

A

Rostral portion of piriform lobe

23
Q

AMYGDALOID BODY
- Targets

A
  • Septal area
  • Hypothalamus
  • Periaqueductal gray (mesencephalon)

via 2 projection pathways:
- Stria terminalis
- Diagonal band

24
Q

AMYGDALOID BODY
- Function

A

Autonomic, endocrine, somatic responses associated with EMOTIONS

E.g. Respiration, circulation, dilation of the iris, gastric motility, micturition, piloerection, and the somatic expressions of fear, rage and aggression.

25
Q

HIPPOCAMPAL FORMATION
- Location

A
  • Deep in the PARAHIPPOCAMPAL GYRUS
  • Forms the medial wall of the temporal horn of the lateral ventricle
26
Q

HIPPOCAMPAL FORMATION
- 3 continuous components (slide 26)

A
  • HIPPOCAMPUS (seahorse shape, connects cingulate gyrus to hypothalamus)
  • DENTATE GYRUS
  • SUBICULUM
27
Q

HIPPOCAMPAL FORMATION
- Where is the hippocampus?

A
  • Caudal to piriform lobe
  • Dorsal to caudal thalamus (adjacent to LGN)
  • Covered by parahippocampal gyrus
28
Q

HIPPOCAMPAL FORMATION
- What is the fornix? (slide 28)

A
  • Fibers from hippocampus + subiculum, coursing below the corpus callosum.
  • Has a fimbria + crus
  • 2 cruras meet at the hippocampal commissure
  • Most fibers project ventrally to mammillary bodies, some to septum
29
Q

HIPPOCAMPAL FORMATION
- Functions

A
  • Learning & memory (short term memory)
  • Spatial orientation
  • Emotions (aggressive behaviors)
30
Q

CINGULATE GYRUS
- Location

A
  • Dorsal to corpus callosum
  • Conuous with septal area (rostrally) and parahippocampal gyrus (caudally)
31
Q

CINGULATE GYRUS
- What is the cingulum?

A
  • White matter (corona radiata) of the cingulate gyrus

made of longitudinal association fibers

32
Q

CINGUALTE GYRUS
- Function

A
  • Suppressive effect on visceral functions regulated by hippocampus
  • Key role in aggressive behavior
33
Q

SEPTAL AREA
- 2 constituents
- Location

A
  • Septal nuclei
  • Subcallosal area

Ventral to genu of corpus callosum

34
Q

SEPTAL AREA
- Afferents & efferents

A

A: medial olfactory tract

E: various limbic system structure
(hippocampus, amygdala, habenular nucleus, hypothalamus)

35
Q

HABENULAR NUCLEUS
- Location

A
  • Rostral to pineal body (lunettes)
  • Dorsal to 3rd ventricle

Part of epithalamus

36
Q

HABENULAR NUCLEUS
- Afferents & efferents

A

A: SEPTAL AREA (via habenularis thalamus) - septum des lunettes
E: INTERCRURAL NUCLEUS (via habenulointercrural tract)

37
Q

ROSTRAL THALAMIC NUCLEUS
- Afferents & efferents

A

A: MAMMILARY BODY (via mammilothalamic tract)
E: adjacent CINGULATE GYRUS + neopallium

38
Q

MAMILLARY BODIES
- Location (paired)

A
  • Ventral surface of hypothalamus
  • Caudal to infundibulum
39
Q

MAMMILARY BODIES
- Connections?

A
  • HIPPOCAMPUS (via fornix)
  • ROSTRAL THALAMIC NUCLEUS (mamillothalamic tract)
  • TEGMENTUM (midbrain) + visceral motor nuclei (medulla) via mamillotegmental tract
  • INTERCRURAL nucleus (via mammillary peduncle)
40
Q

INTERCRURAL NUCLEUS
- Location

A
  • Ventral surface of midbrain
  • Between two crus
41
Q

INTERCRURAL NUCLEUS
- Afferents & efferents

A

A:
- Habenular nucleus (habenulointercrural tract)
- Mammillary body (mammillary peduncle)

E: Brainstem reticular formation

42
Q

Rabies virion will cause Negri bodies (cytoplasmic inclusion) especially in which neurons?

A

Hippocampal neurons

43
Q

4 components of the PAPEZ CIRCUIT

A
  • Hippocampal formation
  • Mammillary body
  • Thalamus
  • Cingulate gyrus
44
Q

Role of the PAPEZ CIRCUIT

A

Regulates emotions and behaviors, via connections with amygdala and septa nuclei

45
Q

Clinical correlations - slides 37…

A

Neuroanatomy (20 decks)

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