Overview of the Brainstem Flashcards
What is the function of the brainstem?
reflexive and unconscious behaviour and modulation of arousal and conscious states
What structures make up the brainstem?
the midbrain, pons and medulla
What are the rostral and caudal boundaries of the brainstem?
extends rostrally from the mamillary bodies to the pyramidally decussation caudally
What can be seen on the dorsal aspect of the brainstem at the level of the midbrain?
the superior and inferior colliculi
What can be seen on the dorsal aspect of the brainstem at the level of the pons?
the cerebellum is connected to the brainstem here with the 4th ventricle between the pons and the cerebellum
What is on the floor of the 4th ventricle?
the facial colliculi - formed by the abducens nucleus and the fibres of the facial nerve
What can be seen on the dorsal aspect of the brainstem at the level of the medulla?
the dorsal columns and the gracile and cuneate tubercles
What can be seen on the ventral aspect of the brainstem at the level of the midbrain?
cerebral peduncles
What can be seen on the ventral aspect of the brainstem at the level of the pons?
cerebelllar peduncles (superior, middle and inferior)
What can be seen on the ventral aspect of the brainstem at the level of the medulla?
inferior olivary nuclei and pyramids descending into the pyramidal decussation
What are the important structures located in the brainstem?
cranial nerve nuclei, reticular formation, long fibre tracts and cerebellar circuitry
What is the tectum?
the tectum is the roof of the brainstem - the dorsal aspect - it is only found in the midbrain and is made up of the inferior and superior colliculi
What is the tegmentum?
the tegmentum is the structure in the brainstem that is continuous with the spinal cord - it is in all part of the brainstem and contains the cranial nerve nuclei and the reticular formation
What is the basis?
the basis is the most ventral part of the brainstem located mostly in the pons - it contains the corticospinal fibre tracts and nuclei related to the cerebellum
Which cranial nerve does not exit the brainstem ventrally?
IV
Which cranial nerves are associated with the brainstem?
III to XII
What is the rule of 4s?
4 cranial nerves exit the medulla (IX-XII), 4 cranial nerves exit the pons (V-VIII) and 4 cranial nerves exit above the pons (I-IV)
Embryologically, where do sensory nerves develop from?
alar plate
Embryologically, where do motor nerves develop from?
basal plate
In the brainstem where are motor nuclei located?
close to the midline
In the brainstem where are sensory nuclei located?
laterally
How are the cranial nerve nuclei organised within the brainstem?
there are 6 columns either side of the midline, the medial 3 are motor and the lateral 3 are sensory. The motor columns are - general somatic motor, brachial motor and general visceral. The sensory columns are - visceral, general somatic and special somatic.
What is the function of caudal part of the reticular formation?
survival reflexes and autonomic functions e.g. breathing, heart rate
What is the function of the rostral part of the reticular formation?
maintain alert conscious state via modulation of forebrain activity
What is the neurotransmitter of the locus coeruleus?
noradrenaline
What is the neurotransmitter of the substantia nigra?
dopamine
What is the neurotransmitter of the dorsal raphe nucleus?
serotonin
What are the 3 major pathways that traverse the brainstem?
dorsal column medial lemniscus pathway (fine touch), anterolateral system (pain), corticospinal tract (movement)
Where does the dorsal column medial lemniscus pathway cross the midline?
in the medulla at the medial lemniscus
Where does the anterolateral system cross the midline?
in the spinal cord
Where does the anterolateral system terminate?
three pathways each terminate in different regions- the thalamus, midbrain and reticular formation
Where does the corticospinal tract cross the midline?
the pyramidal decussation
What does the dorsal aspect of the brainstem contain?
cranial nerve nuclei and reticular formation
What does the ventral aspect of the brainstem contain?
corticospinal tracts, cerebral peduncles, substantia nigra, red nuclei, cerebellar nuclei, cerebellar peduncles, inferior olivary nuclei
