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BRAIN AND BEHAVIOUR > Histology: Organisation of the Brainstem and Cranial Nerves > Flashcards

Histology: Organisation of the Brainstem and Cranial Nerves Flashcards

1
Q

Describe the dorsal (posterior) view of the midbrain

A

Superior and inferior colliculi are visible

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2
Q

Describe the ventral (anterior) view of the midbrain

A

Cerebral peduncles are visible which contain the corticopontine and corticospinal tracts

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3
Q

What are the 3 cerebellar peduncles?

A

Superior, middle and inferior cerebellar peduncles

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4
Q

Describe the superior cerebellar peduncle

A

Obvious at the rostral (superior) pons and is the major output path from the cerebellum

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5
Q

Describe the middle cerebellar peduncle

A

Carries afferent input from the pontine nuclei

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6
Q

Describe the inferior cerebellar peduncle

A

Pathway for inputs from the inferior olivary nucleus (and others) to the cerebellum

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7
Q

What is the role of the superior colliculus?

A

Involved in eye movement and direction of visual attention

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8
Q

What is the role of the inferior colliculus?

A

A component of the auditory pathway

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9
Q

Describe the dorsal (posterior) view of the pons

A

There are cerebellar peduncles which attach the caudal (tail-end) pons to the cerebellum, while, medially, there is the floor of the 4th ventricle

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10
Q

Describe the ventral (anterior) view of the pons

A

Can see the basal pons (whole structure anteriorly) which consists of transverse and descending fibres as well as pontine nuclei

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11
Q

Describe the dorsal (posterior) view of the medulla

A

Anteriorly and medially, the floor of the 4th ventricle continues from the pons in the ‘open’ part of the medulla, until it closes and forms the central canal

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12
Q

Describe the ventral (anterior) view of the medulla

A

Two wedge-shaped pyramids (site of corticospinal tract and decussation) and the olive (bulge on the side of pyramids) that contains the olivary nucleus which is important projection from the olivary nucleus to the cerebellum

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13
Q

How can you tell if it’s the midbrain?

A

If you can see colliculi (little hills) and it’s the most superior aspect of the brainstem

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14
Q

How can you tell if it’s the pons?

A

If you can see its prominent basal part and attached cerebellum

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15
Q

How can you tell if it’s the medulla?

A

If it’s the most inferior aspect and it’s continuous with the spinal cord

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16
Q

What is present generally in the dorsal brainstem?

A

Cranial nerve nuclei

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17
Q

What is relative positioning of motor and sensory nuclei in the dorsal portion of the brainstem?

A

Motor nuclei are more medial, sensory nuclei are more laterally positioned

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18
Q

What is present generally in the middle transverse part of the brainstem?

A

Ascending pathways (sensory tracts) and various nuclei of the reticular formation

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19
Q

What is present generally in the ventral brainstem?

A

Fibres of the descending pathways

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20
Q

Describe the organisation of motor fibres in the ventral portion of the basal pons

A

In the basal pons the motor fibres are interspersed with the pontine nuclei

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21
Q

Describe the organisation of motor fibres in the midbrain and medulla

A

Form independent motor fibre collections in the midbrain (cerebral peduncles) and medulla (pyramids)

22
Q

What are the 4 principle functions of the reticular formation?

A
  1. Arousal responses
  2. Autonomic nervous system control
  3. Control of muscle tone and reflexes
  4. Pain modulation
23
Q

What is the role of the lateral portion of the reticular formation?

A

Sensory - it has afferent inputs from special senses

24
Q

What is the role of the medial portion of the reticular formation?

A

Motor - it provides efferent output to the midbrain, hypothalamus, thalamus and spinal cord

25
Q

What is the role of the midline portion of the reticular formation?

A

Inhibitory - involved in inhibitory responses

26
Q

What is the function of the medial longitudinal fasciculus (MLF)?

A

Connects the brainstem ‘gaze centres’ and the vestibular system in order to allow coordination of eye movements and maintenance of gaze with head movement (VOR reflex). Lies just below the PAG in the midbrain

27
Q

What is the periaqueductal gray (PAG)?

A

Involved in descending pain control and regulation of autonomic functions, and this is circular-shaped and dorsally located in the midbrain

28
Q

Which non-cranial nuclei are present in the rostral (superior) midbrain?

A

Red nucleus and substantia nigra

29
Q

What is the red nucleus present in the rostral midbrain?

A

A motor nucleus linked to the cerebellum through the inferior olivary nucleus

30
Q

What is the substantia nigra present in the rostral midbrain?

A

Important in motor function as its part of the basal ganglia and its compact part has dopaminergic neurones that degenerate in Parkinson’s disease

31
Q

What fibre types are present in the cerebral peduncle of the caudal midbrain?

A

Corticospinal, corticopontine and corticobulbar fibres

32
Q

Where do cerebellar output fibres, from the superior cerebellar peduncles of the caudal midbrain, travel?

A

Travel superiorly to the red nucleus and thalamus

33
Q

Describe the transverse structure of the rostral pons

A

Superior cerebellar peduncle prominent in dorsal brainstem here and the 4th ventricle is formed from the cerebral aqueduct with most caudal periaqueductal gray (PAG) surrounding it ventrally

34
Q

Describe the transverse structure of the caudal pons

A

Cerebellar physically attached here, mainly by the middle cerebellar peduncles

35
Q

Where is the 4th ventricle widest?

A

At the junction of the pons and medulla

36
Q

Describe the transverse structure of the rostral medulla

A

Has inferior olivary nucleus with crossing internal arcuate fibres (IAF) entering the inferior cerebellar peduncle, dorsal aspect there is the 4th ventricle (forms the central canal caudally) and contains the spinal nucleus of the trigeminal nerve (Vn) - pain and temperature from the head

37
Q

Describe the transverse structure of the caudal medulla

A

Holds the dorsal column nuclei: nucleus gracilis (NG)and nucleus cuneatus (NC) and spinothalamic axons laterally

38
Q

What characterises the transverse structure of the medulla?

A

Ventral, wedge-shaped pyramids (corticospinal tract)

39
Q

Where do cranial nerves VI-VIII join the brainstem?

A

Ponto-medullary junction

40
Q

Which cranial nerves are solely sensory?

A

CN I, II and VIII (olfactory, optic, vestibulocochlear)

41
Q

Which cranial nerves are solely motor?

A

CN III, IV, VI, XI, XII (oculomotor, trochlear, abducens, spinal accessory and hypoglossal)

42
Q

Which cranial nerves are both motor and sensory?

A

CN V, VII, IX, X (trigeminal, facial, glossopharyngeal and vagus)

43
Q

Where do the spinal afferents for the muscles of mastication have heir cell bodies?

A

In the midbrain nucleus of V (trigeminal nucleus)

44
Q

Describe the organisation from medial to lateral of the spinal cord nuclei

A

Somatic LMN nuclei, visceral motor neurone nuclei, visceral sensory neurone nuclei then somatic sensory nuclei (most lateral)

45
Q

Which part of the brainstem is associated with the pupillary and accommodation reflexes?

46
Q

Which part of the brainstem is associated with the blink reflexes?

47
Q

Outline the physiology of the gag reflex

A

Afferent neurone is the glossopharyngeal nerve and the efferent neurone is the vagus nerve

48
Q

Which part of the brainstem is associated with the gag reflex?

49
Q

Describe the blood supply to the caudal medulla

A 
Anteriorly = anterior spinal artery (most anterior) and vertebral artery
Posteriorly = posterior spinal artery (most posterior) and posterior inferior cerebellar artery (PICA)
50
Q

Describe the blood supply to the rostral medulla

A 
Anteriorly = anterior spinal artery (most anterior) and vertebral artery
Middle = vertebral artery 
Posterior = PICA
51
Q

Describe the blood supply to the middle pons

A 
Anterior = basilar artery
Posterior = anterior inferior cerebellar artery (AICA)
52
Q

Describe the blood supply to the midbrain

A 
Anterior = basilar artery
Posterior = posterior cerebral artery

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