Lecture 9: Brainstem and Cranial Nerves Flashcards
What is the brainstem made up of?
- midbrain
- pons
- medulla
What pathways pass through the brainstem?
ALL ascending and descending pathways
How is the cerebellum connected to the brainstem?
By 3 cerebellar peduncles (white fibre tracts)
Which cranial nerve nuclei are contained within the brainstem?
9 of the 12 pairs
III, IV, V, VI, VII, VIII, IX, X and XII
How are the pathways related to the brainstem?
- many of descending pathways synapse in brainstem nuclei before going to body
- many ascending pathways synapse here before going to the brain
- some start within nuclei of the brainstem
Describe the internal structure of the brainstem.
POSTERIOR –> ANTERIOR
- tectum (roof) sits behind relevant ventricular system depending on how far down the brainstem the section is
- ventricular system (e.g. cerebral aqueduct or 4th ventricle)
- tegmentum
- base
Name some visible structures from the posterior aspect of the brainstem.
- pineal gland
- superior colliculus
- inferior colliculus
- trochlear nerve (CN IV)
- dorsal columns
Why are there enlargements in the dorsal columns?
Cuneate and gracile pathways synapse here onto their nuclei (which contain cell bodies of secondary sensory nerves), (cross over to other side before going up to the brain) hence enlargement
What forms the roof of the 4th ventricle?
the cerebellum
What does the pineal gland do?
produces melatonin (important for sleep and circadian rythym)
What do the colliculi do?
Superior colliculus - involved in visual pathway
Inferior colliculus - involved in auditory pathway
Name some visible structures from the anterior aspect of the brainstem.
- optic chiasm
- pituitary stalk
- mammillary body
- cerebral peduncle
- medullary pyramids
- pyramidal decussation
What is the pyramidical decussation?
Point at which fibres from motor cortex cross over
What are the medullary pyramids?
contain corticospinal axons
What is the difference between an optic nerve and optic tract?
the optic tract has axons coming from both eyes whereas the optic nerve has axons from one eye