What is the gateway between the spinal cord and higher cortical areas?
What are the two major functions of the brainstem?
Reflexive and unconscious behaviour
Modulation of various arousal and conscious states
Where is the brainstem located?
In the posterior cranial fossa, extending from the mammillary bodies to the pyramidal decussation caudally.
What are the 3 divisions of the brainstem?
Midbrain, pons and medulla
What are the two pairs of characteristic bumps on the dorsal aspect of the midbrain?
The superior and inferior colliculi
Which part of the brainstem does the cerebellum attach to?
What is the pons limited by?
The 4th ventricle
Which parts of the pons form the floor of the 4th ventricle?
The facial colliculi
What forms the facial colliculi
Abducens nucleus and fibres of CNVII (facial nerve)
What forms the dorsal aspect of the caudal medulla?
Dorsal columns and nuclei, forming the gracile and cuneate tubercles
What can be seen on the ventral aspect of the midbrain?
Cerebral peduncles with the interpeduncular fossa in between.
What can be seen on the ventral aspect of the pons?
The superior, middle and inferior cerebellar peduncles dorsolaterally attaching to the cerebellum.
What can be seen on the ventral aspect of the medulla?
Rostral: Inferior olivary nuclei
Pyramids descending to the pyramidal decussation
What is the tectum?
The "roof" of the midbrain - the dorsal part. It refers solely to the colliculi of the midbrain.
What forms the roof of the 4th ventricle?
The 4 colliculi, i.e. the tectum.
What is the tegmentum?
Where the spinal cord continues up into the brainstem - continous with the spinal cord.
Structures within the tegmentum go to the spinal cord.
These include the cranial nerves and reticular formation.
What is the basis?
The basillar pons - the anterior portion of the pons.
Important for descending motor control, e.g. attachments to cerebellum, from cerebellum to other nuclei and tracts important for motor systems.
Which part of the brainstem only applies to the colliculi and midbrain?
Which part of the brainstem is a continuation of the spinal cord that travels throughout the entire brainstem?
What does the tegmentum occupy?
Middle part of the midbrain
Dorsal part of the pons and medulla
What does the tegmentum contain?
Nuclei for the cranial nerves and the reticular formation.
What is the sole focus of the basis?
Where do the spinal nerves end?
Which spinal cord segment lacks a dermatome?
What do the spinal nerves supply?
What do the cranial nerves supply?
Somatic and visceral motor and sensory information to head
Which cranial nerves also supply visceral sensory and motor innervation to neck, chest and most abdominal organs?
CNIX and X
Which side of the brainstem do most cranial nerves exit?
Which cranial nerve does not exit the brainstem on the ventral surface?
Which cranial nerves are exclusively motor?
CNIII, IV and VI (control the eye) CNXI and XII
Which cranial nerves are exclusively sensory?
CNI, II and VIII
Which cranial nerves are mixed?
CNV, VII, IX and X
What is the rule of 4 for the cranial nerves?
4 cranial nerves exit the medulla: CNIX-XII
4 exit the pons: CNV, VI, VII, VIII
4 exit above the pons: CNIII, IV
Where do the cranial nerve nuclei lie during embryological development?
Adjacent to the ventricular system
Which plate do the sensory nuclei develop from?
Which plate do the motor nuclei develop from?
How are the positions of the cranial nerve nuclei determined?
As the 4th ventricle develops, the alar plate (sensory nuclei) is pushed to the side, now sitting more lateral to the basal plate (motor nuclei).
How are cranial nerve nuclei grouped?
Based on function
Which nuclei are closer to the midline?
Motor nuclei (motor column)
Which nuclei are positioned laterally?
Sensory nuclei (sensory column)
How are the sensory and motor nuclei grouped within the brainstem?
Into 3 medial motor columns and 3 lateral sensory columns.
What are the 3 motor columns (medial to lateral)?
General somatic motor
What are the 3 sensory columns (medial to lateral)?
General and special visceral
Which nucleus is this?
What is the tegmentum continuous with rostrally?
Certain nuclei in the thalamus
What is the tegmentum continuous with caudally?
Intermediate grey of the spinal cord
What is the function of the tegmentum rostrally (midbrain and upper pons)?
Mantains alert conscious state.
What is the function of the tegmentum caudally (pons and medulla)?
Work together with cranial nerve nuclei and spinal cord to carry out a variety of important motor reflex and autonomic functions. Closer to spinal cord, therefore more spinal cord-like actions.
What is the ascending reticular activating system?
Long projection systems from the rostral tegmentum.
What 4 different systems does the ascending reticular activating system use?
Noradrenergic (locus cereleus)
Dopaminergic (e.g. substantia nigra)
Serotonergic (dorsal raphe nucleus)
What functions does the caudal reticular formation serve crucial functions in?
Motor reflex and autonomic functions
What does the ventrolateral medullary (VLM) reticular formation do?
Regulates the visceral functions of CNX (Vagus): G
I responses (swallowing, vomiting)
Rhythm, coughing, hiccupping, sneezing
What is the lateral medullary pontine reticular formation important for?
What is the region of the reticular formation surrounding the facial nucleus important for?
Crying and smiling
What are the 3 major pathways traversing the brainstem?
- Dorsal column-medial lemniscus system
- Anterolateral system
- Corticospinal tract
Which sensory modality is the dorsal column-medial lemniscus system for?
Fine touch-tactile, vibration
Where does the dorsal column-medial lemniscus system decussate?
In the medulla, at the medial lemniscus
Which sensory modality is the anterolateral system for?
Pain and temperature
Where does the anterolateral system terminate?
In 3 different regions: thalamus, midbrain and reticular formation.
What is the function of the corticospinal tract?
Where does the corticospinal tract decussate?
At the pyramids
What do the dorsal aspects of the brainstem contain?
Cranial nuclei and reticular formation
What do the ventral (basis) aspects of the brainstem contain?
Structures associated with the descending motor tracts (corticospinal tracts).
Midbrain: cerebral peduncles, substantia nigra, red nuclei
Pons: CB nuclei, middle cerebellar peduncle
Medulla: inferior olivary nuclei