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Neuroanatomy > Special senses > Flashcards

Special senses Flashcards

1
Q

Where does the vestibulocochlear nerve [VIII] enter the brainstem?

A

Cerebellopontine angle

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2
Q

What is the structure of the auditory pathway?

A
  1. Fibres of the vestibulocochlear nerve [VIII] begin at the cochlea (from the hair cells) and travel to the brainstem via the internal acoustic meatus.
  2. Once the fibres reach the brainstem, they enter at the cerebellopontine angle and bifurcate, giving branches to the ventral and dorsal cochlear nuclei (on dorsolateral surface of medulla).
  3. Fibres from these nuclei (mainly ventral cochlear nuclei) then project to bilateral superior olivary complexes(SOC) next to medial lemniscus in pons.
  4. Fibres from the SOC and cochlear nuclei (that bypass the SOC) form the lateral lemniscus and ascend through the pons to terminate in the inferior colliculus (in tectum of midbrain).
  5. From IC, fibres project into the medial geniculate body of the thalamus.
  6. The thalamus then sends multiple fibres to the auditory cortex (in temporal lobe) in the auditory radiation through the internal capsule.
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3
Q

What are the vestibular nuclei?

A
  1. Superior
  2. Inferior
  3. Medial
  4. Lateral
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4
Q

Where do fibres from the superior vestibular nuclei project?

A

Thalamus

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5
Q

Where do fibres from the lateral vestibular nuclei project?

A

Vestibulospinal tract

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6
Q

What is the location of the primary auditory cortex?

A
  • Lateral temporal lobe
  • Brodmann’s area 41, 42
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7
Q

What are the components of cortex involved in olfactions?

A
  1. Anterior olfactory nucleus → Anterior commissure → Contralateral olfactory bulb: Takes part in inhibition of contralateral bulb.
  2. Olfactory tubercle → Medial dorsal nucleus of the thalamus → Orbitofrontal cortex: Conscious perception of smell.
  3. Pyriform cortex: Projects into other olfactory cortical regions.
  4. Amygdala → Reticular formation: Mediates arousal.
  5. Amygdala → Hypothalamus: Mediates autonomic responses.
  6. Entorhinal cortex → Hippocampus: Mediates motivation.
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8
Q

What is the structure of the visual pathway?

A
  1. The optic nerve (containing fibres from ganglion cells) enters the skull through the optic canal.
  2. Fibres from the nasal retina decussate at the optic chiasm to form the optic tract.
  3. Optic tract fibres project into a number of different structures, but mainly the lateral geniculate nucleus (LGN) in the thalamus.
  4. From the LGN, fibres project into layer IV of the primary visual cortex (V1) via the optic radiation.
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9
Q

Aside from the LGN, what other areas of the brain do fibres of the optic tract project into?

A
  1. Pretectal region in rostral midbrain: Involved in pupillary reflex.
  2. Suprachiasmatic nucleus in hypothalamus: Involved in regulating circadian rhythms.
  3. Superior colliculus in midbrain: Involved in controlling movements of the eyes.
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10
Q

What is the stria of Gennari?

A

White strip running through grey matter of V1 representing dense axonal input into layer IV.

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11
Q

What is the medial longitudinal fasciculus (MLF)?

A

Bundle of fibres running in the midline of the brainstem from the various motor nuclei of the eyes to cervical spinal cord.

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12
Q

What is the function of the MLF?

A

Controls tracking movements of the eyes and head, allowing moving objects to be followed witout retinal slip by:

  1. Connecting vestibular nuclei to motor nuclei of eyes (mediates vestibulo-ocular reflex)
  2. Connecting superior colliculus with muscles of neck to control eye movement
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13
Q

What are the location of the eye motor nuclei?

A
  1. Oculomotor nucleus: In midbrain at level of superior colliculus
  2. Trochlear nucleus: In midbrain inferior to the cerebral aqueduct
  3. Abducent nerve: In pons at level of floor of 4th ventricle
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14
Q

How are eye movements made?

A
  1. Eye movements are initiated in eye-fields of the frontal and parietal cortices.
  2. Fibres from the cerebral cortex project into the superior colliculus.
  3. Fibres from the SC then project into gaze centres of the reticular formation of the pons. These translate the position of the object into the appropriate eye movements required to bring the object into the centre of the retina.
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15
Q

What is the location of the primary visual cortex?

A
  • Occipital lobe
  • Calcerine sulcus
  • Brodmann’s area 17
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16
Q

What are the groups of nuclei present in the thalamus?

A
  1. Anterior group
  2. Medial group
  3. Ventral group
  4. Geniculate nuclei
17
Q

What are the components of the ventral group of the thalamus?

A
  1. Ventro-anterior nucleus
  2. Ventro-lateral nucleus
  3. Ventro-posterior nucleus
18
Q

What is the function of the ventro-posterior nucleus of the thalamus?

A

Relay for ascending somatosensory fibres destined for S1

19
Q

What is the function of the ventro-lateral nucleus of the thalamus?

A

Relay for fibres from cerebellum and basal ganglia to M1

20
Q

What is the function of the ventro-anterior nucleus of the thalamus?

A

Relay for fibres from from the cerebellum and basal ganglia to the secondary motor areas (premotor + supplementary motor)

21
Q

What are the functions of the anterior nuclei of the thalamus?

A

Possibly mediates perception of emotional states (relay for fibres from the mammillary bodies to the cingulate cortex, part of Papez’s circuit)

22
Q

What are the components of medial group of the thalamus?

A
  1. Medial nuclei
  2. Pulvinar
23
Q

What are the functions of the medial group of the thalamus?

A
  • Receives fibres from wide range of different sources in cerebral cortex and projects into various assoication cortices
  • Medial nuclei → Pre-frontal cortex
  • Pulvinar → Temporo-parietal-occipital association areas
24
Q

What is the anterior perforated substance?

A
  • Area anterior to optic chiasm consisting of a mix of grey and white matter
  • Contains many perforations that represent blood vessels
  • It is the point of entry into cortex for triate arteries supplying the striatum and internal capsule
25
Q

What are the functions of the different layers of neocortex?

A
  • Layer I: Few nerve fibres
  • Layer II & III: Projections into other cortical areas
  • Layer IV: Projections from the thalamus
  • Layer V: Projections into subcortical areas (e.g. spinal cord)
  • Layer VI: Projections into the thalamus
26
Q

What is the histological structure of neocortex?

A
  1. Molecular layer (layer I): Contains mainly axons and very few cell bodies
  2. Outer granular layer (layer II): Contains small rounded neurones
  3. Outer pyramidal layer (layer III): Contains large pyramidal neurones that project to other cortical areas
  4. Inner granular layer (layer IV): Contains cells that receive inputs from thalamus
  5. Inner pyramidal layer (layer V): Contains pyramidal neurones that project to subcortical areas
  6. Multiform layer (layer VI): Conains a few scattered cells projecting into the thalamus
27
Q

What are the distinct histological characterstics of primary sensory cortex?

A
  • Layer IV is thick and well developed as a lot of inputs are received
  • Output layers (layer V, VI) are thin and poorly developed
28
Q

What are the distinct histological characterstics of primary motor cortex?

A
  • Thick and well developed output layers (esp. layer V) due to large number of output cells
  • Thin and poorly developed input layers (layer IV)
29
Q

What are the different type of cortex?

A
  • Neocortex (6 layers): Sensory, motor and association cortices
  • Paeleocrotex (3 layers): Hippocampus, olfactory cortex
  • Juxtallocortex (4-5 layers): Parahippocampal, cingulate gyri
30
Q

What are the types of olfactory defects?

A
  1. Anosmia: Inability to detect odours
  2. Hyposmia: Decreased ability to detect odours
  3. Dysosmia: Poor identification of odours
31
Q

What are the types of dysosmia?

A
  1. Phantosmia: Perception of smell when odourants are absent
  2. Olfactory agnosia: Ability to detect odourants but inability to identify them
32
Q

What condition commonly affects the MLF?

A

Multiple sclerosis

33
Q

What are the oculomotor defects experienced in MS?

A
  1. Nystagmus
  2. Diplopia
  3. Gaze control defects
34
Q

What is retrosigmoid craniostomy?

A

Removal of bone of skull posterior to sigmoid sinus and inferior to transverse sinus to access the lateral cerebellum and cerebellopontine angle.

35
Q

What condition is commonly treated with retrosigmoidal craniotomy?

A

Ependymoma

Neuroanatomy (7 decks)

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