2.13 - Brainstem and Cranial Nerves Flashcards
What does the brainstem consist of?
- midbrain
- pons
- medulla
What is the use of the brainstem in terms of nerve pathways?
- all ascending and descending pathways pass through the brainstem
- many synapse here in relay nuclei or arise directly from/synapse in other brainstem nuclei
- contains 9 of 12 pairs of cranial nerves (no I, II, XI)
How is the cerebellum connected to the brainstem?
By three cerebellar peduncles which are white fibre tracts
What is the internal structure of the brainstem (axial image, from posterior to anterior)?
- tectum (roof)
- ventricular system - connection between third and fourth ventricle
- tegmentum - below roof
- base - two sections at the anterior
What can you see from posterior aspect of brainstem? (top to bottom, half cerebellum removed)
- pineal gland
- superior colliculus
- inferior colliculus
- trochlear nerve
- dorsal columns
What can you see from anterior aspect of brainstem? (top to bottom, half cerebellum removed)
- optic chiasm
- pituitary stalk
- mammillary body
- cerebral peduncle
- medullary pyramids
- pyramidal decussation
What descending tracts go through the cerebral peduncles?
Corticospinal and corticobulbar tracts taking voluntary information from motor cortex down to lower motor neurones of brain stem/spinal cord
What does a section of the midbrain look like? (axial/horizontal section, posterior to anterior)
- superior (visual) and inferior (auditory) colliculi
- aqueduct
- cerebral peduncle
- cranial nerves III & IV emerge at this level of the midbrain
What does a section of the pons look like? (axial/horizontal section, posterior to anterior)
- fourth ventricle (aqueduct become fourth ventricle)
- middle cerebellar peduncle
- cranial nerves V, VI, VII & VIII emerge at this level
- also contains pontine nuclei, transverse fibres and descending pathways
What does a section of the open (upper) medulla look like? (posterior to anterior)
- fourth ventricle - moved more posterior
- called the open medulla as the fourth ventricle has no roof at this level
- inferior olivary nucleus
- cranial nerves IX, X & XII emerge from medulla
What does a section of the closed (lower) medulla look like? (posterior to anterior)
- dorsal columns
- central canal - continuation of the fourth ventricle - fourth ventricle turned into central canal and tissue all the way around it
- decussation of pyramids
- cranial nerves IX, X & XII emerge from medulla
Overview of anatomy of the medulla
- rostral continuation of spinal cord
- anterior surface has pyramids (descending tracts)
- posterior surface has dorsal columns
- posterior surface divided into open and closed
- closed has extension of central canal of spinal cord
- canal widens to form fourth ventricle in open medulla
What two arterial systems is the CNS blood supply divided into?
- anterior supply - derived from internal carotid system - supplies most of the cerebral hemispheres
- posterior supply - derived from vertebrobasilar - supplies most of the brainstem
Brainstem blood supply - vessels involved (top to bottom)
- anterior cerebral artery
- carotid artery
- middle cerebral artery
- posterior communicating artery
- posterior cerebral artery
- (those form Circle of Willis)
- superior cerebellar artery
- basilar artery
- anterior inferior cerebellar artery
- posterior inferior cerebellar artery
- anterior spinal artery
- posterior spinal artery
- vertebral artery
-(these seven form vertebrobasilar system)
Nuclei of cranial nerves
- efferent (motor) nuclei - cranial nerves pick up fibres coming from the nuclei and take them to their destinations in one of the cranial nerves
- afferent (sensory) nuclei - receive sensory fibres
- roughly aligned / at same level
