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3: Organisation of the nervous system/ bit of development Flashcards

1
Q

Define the brainstem

A

The brainstem is part of the brain exclusive of the cerebellum that lies between cerebrum and the spinal cord.

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2
Q

What are the three major divisions of the brainstem from top to bottom?

A

Midbrain
Pons
Medulla Oblongata

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3
Q

What is the location and function of the pineal gland?

A

The pineal gland is in the midline, superior to both colliculuses and releases melatonin and is important in regulating circadian rhythm (sleep/wake cycles)

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4
Q

Describe the position of the pons relative to 4th ventricle

A

The pons is the floor of the 4th ventricle

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5
Q

Where are the colliculi found and what are their function?

A

They are found at the roof of the midbrain
Sup. colliculus: coordination of eye and head movements at same time.
Inf. colliculus: auditory reflexes e.g. turning your head in a direction of a loud sound.

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6
Q

How many cranial nerves emerge from the back of the brainstem?

A

Only one, being the trochlear nerve, CNIV, which supplies the extrinsic muscles of the eye, superior oblique muscle

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7
Q

What structure defines the medulla in the dorsal aspect (back) of the brain?

A

Dorsal columns, which are involved in two main sensory pathways being touch and proprioception.

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8
Q

Why is the pons very clear?

A

You get the transverse fibres going across it seen in anteroinferior view of the brainstem
Above this is midbrain and below is medulla oblongata.

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9
Q

What three structures can be seen superior to the pons in the anteroinferior view of the brainstem from sup. to inf. ?

A

Optic chiasm
Pituitary stalk (infundibulum)
Mamillary bodies

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10
Q

What are mamillary bodies?

A

Inf. part of hypothalamus, involved in limbic system

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11
Q

Which cranial nerve emerges just superior to the transverse fibres of the pons ?

A

Occulomotor nerve CN III

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12
Q

Which extrinsic muscles of the eye does CNIII innervate?

A 
Sup. rectus
Inf. rectus
medial rectus
inferior oblique
(all except sup. oblique and lateral rectus)
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13
Q

What does the midbrain consist of?

A

Cerebral penducle

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14
Q

What is cerebral penducle?

A

Main motor fibres coming from the cerebral cortex down to the spinal cord.
Descending motor tracts from motor cortex

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15
Q

Function of cerebral penducle?

A

Functional and structural role, holds the cerebrum onto the brainstem

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16
Q

Which cranial nerve emerges from the lateral aspect of the pons?

A

Trigeminal CNV

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17
Q

What is the function of the trigeminal nerve?

A

Touch and sensation head and neck
Small root next to the larger one as it emerges from transverse fibres that provides motor supply to the muscles of mastication

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18
Q

Which 3 nerves emerge at the ponto-medullary level?

A

Abducens CN VI (most medial)
Facial CN VIII (more lateral)
Vestibulocochlear CN VIIII

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19
Q

What is the function of abducens?

A

supplies lateral rectus muscle abduction from the midline

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20
Q

What is the function of the facial nerve?

A

facial muscles involved in expression

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21
Q

What is the function of the vestibulochlear?

A

balance and hearing

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22
Q

What is Bell’s palsy?

A

Loss of facial tone due to dysfunction of the facial nerve

23
Q

What is the distinguishable feature of the medulla oblongata?

A

pyramids on the anterior surface which are the re-emergence of fibres

24
Q

Which 3 nerves originate from the lateral medulla and give general function

A

Glossopharyngeal IX - sensory and motor innervation of tongue and pharynx
Vagus X - parasymp to viscera
Accessory XI - sternocleidomastoid and trapezius

25
Which other nerve emerges seperately?
Hypoglossal (XII), innervates the musculature of the tongue
26
What is the pyramidal decussation?
90-95% of fibres cross over at the base of the medulla
27
What are the four functional sub-types of cranial nerves?
``` General somatic afferent (GSA) sensation from skin/mucous membranes General visceral afferent (GVA) sensation from GI, heart, vessels, lungs General somatic efferent (GSE) muscles for eye and tongue movements General visceral efferent (GVE) preganglionic parasympathetic ```
28
Describe the special subtypes of cranial nerves and what are their actions
Special SA: vision, hearing and equilibrium Special VA: smell(cn1), taste (3 cranial nerves that all go back to the nucleus solitarius) Special VE: chewing, facial expression, swallowing, vocal sounds, turning head
29
What does CNS develop from?
neuroepithelium (wall of the neural tube)
30
What does PNS develop from?
Neural crest
31
Describe differentiation of neuroepithelium
neuroblasts(all neurons with cell bodies in CNS) glioblasts(astrocytes, oligodendrocytes) ependymal cells - lining ventricles and central canal
32
Describe the differentiation of neural crest cells
Sensory neurons of dorsal root ganglia postganglionic autonomic neurons schwann cells non-neuronal derivatives e.g. melanocytes
33
Describe the initial formation of the nervous system
The ectoderm over the trilaminar embryonic disc thickens to form neural plate The sides of the neural plate fold dorsally to form neural folds which fuse to form neural tube Neural crest forms along either side of the neural tube
34
Which neurons are found in the alar plate of embryonic spinal cord?
Interneurons
35
What structure separates the sensory nuclei from the motor nuclei in the spinal cord and brainstem?
Sulcus limitans,
36
What happens in the formation of the rhombencephalon and how does this affect the arrangement of the nuclei?
The alar plate opens up and a ventricle forms This opening of the alar plate results in the motor nuclei being medial in the brainstem and the sensory nuclei are lateral
37
Describe the arrangement of the different groups in columns within the brainstem.
Motor – Medial Sensory – Lateral Motor – arranged in columns from medial to lateral in this order: GSE, SVE, GVE Sensory – arranged in columns from medial to lateral in this order: GVA/SVA, GSA, SSA
38
26. State the nuclei that are in the general somatic efferent group and describe their location within the brainstem.
* Oculomotor = midbrain * Trochlear = midbrain * Abducens = pons (though it emerges at the ponto-medullary junction) * Hypoglossus = medulla
39
27. State the nuclei that are in the special visceral efferent group and describe their location within the brainstem.
* Trigeminal = pons * Facial = pons * Ambiguus = medulla * Accessory = cervical spinal cord * NOTE: ambiguus is a group of large motor neurons situated deep in the medullary reticular formation. It contains cell bodies of nerves that innervate muscles of the soft palate, pharynx and larynx – strongly associated with speech and swallowing
40
28. State the nuclei that are in the general visceral efferent group and describe their location within the brainstem.
* Edinger Westphal = midbrain * Salivatory = ponto-medullary border (there are THREE sets of salivatory nuclei) * Vagus = pons
41
29. State the nuclei that are in the special somatic AFFERENT group and describe their location within the brainstem.
Vestibulocochlear = pons and medulla
42
30. State the nuclei that are in the general somatic AFFERENT group and describe their location within the brainstem.
Trigeminal = in all three parts and in the cervical spinal cord
43
31. State the nuclei that are in the general visceral AFFERENT and special visceral AFFERENT groups and describe their location within the brainstem.
Solitarius – mainly in the medulla (but a little bit in the pons)
44
32. Describe the appearance of a cross-section of the midbrain. What are the key features seen?
It has a distinctive ‘mickey mouse’ appearance Ears of Mickey Mouse are the cerebral peduncles At the point where the cerebral peduncles meet the rest of the midbrain you find the substantia nigra You will see the cerebral aqueduct in the middle (small diamond shape) The two rounded protrusion on the opposite side of the cerebral peduncles are the inferior colliculi
45
33. What is the substantia nigra? Describe its clinical significance.
The substantia nigra is a group of dopaminergic neurons In their normal metabolism they produce neuromelanin, which gives the black colour of the substantia nigra Parkinson’s disease is caused by loss of these dopaminergic neurons so patients with Parkinson’s will have a pale substantia nigra
46
34. Describe the appearance of a cross-section of the pons. What are the key features seen?
The 4th ventricle will be seen at the dorsal aspect of the pons The most distinctive feature are the transverse fibres On either side you will see the middle cerebellar peduncles
47
35. What is the difference between the peduncles seen in the midbrain and the ones seen in the pons?
Midbrain – cerebral peduncles | Pons – cerebellar peduncles
48
36. Describe the appearance of a cross-section of the medulla. What are the key features seen?
Pyramids will be seen on the ventral aspect The inferior olivary nucleus will be found next to the pyramids The 4th ventricle will still be visible
49
37. What is the role of the inferior olivary nucleus?
It is involved in fine tuning motor function
50
38. Describe the appearance of a cross-section of the lower medulla. What are the key features seen?
It will be more round The central canal will be seen in the middle The dorsal columns will be seen on the dorsal side The pyramidal decussation may be seen
51
39. Name the two columns that make up the dorsal columns.
Gracilis – more medial – sensory information from the lower limb Cuneatus – more lateral – sensory information from the upper limb
52
40. What is lateral medullary syndrome? Describe and explain the symptoms.
It is a constellation of symptoms caused by an occlusion in the vertebral arteries or the posterior inferior cerebellar arteries (PICA) It causes: • Horner's Syndrome – disturbing the sympathetic tract • Vertigo – because of disturbing the vestibular nucleus • Ipsilateral loss of pain/thermal sensation on the face – disturbing the spinothalamic tract • Contralateral loss of pain/thermal sensation on the trunk and limbs – disturbing the spinothalamic tract • Ipsilateral cerebellar ataxia – disturbing the inferior cerebellar peduncle
53
41. What are the symptoms of Horner’s Syndrome?
Ptosis (drooping of upper eyelid) Loss of sweating around the eye Hoarseness Difficulty Swallowing

Neuro (17 decks)

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