Overview of brainstem organisation Flashcards
What does the brainstem act as a gateway between?
Spinal cord and higher cortical areas
What are the functions of the brainstem?
Reflexive and unconscious behaviour
Modulation of various arousal and conscious states
What are the three major components of the brainstem?
Midbrain
Pons
Medulla
Describe the location of the brainstem?
Posterior cranial fossa
Extends from mamillary bodies rostrally to pyramidal decussation caudally
Describe the characteristic features of the midbrain, pons and medulla on the dorsal aspect of the brainstem?
Midbrain: superior and inferior colliculi
Pons: limited by fourth ventricle, facial collculi
Medulla: dorsal columns, nuclei-gracile and cuneate tubercle
Which part of the brainstem connects to the cerebellum?
Pons
Describe the characteristic features of the mibrain, pons and medulla on the ventral aspect of the brainstem?
Mibrain: cerebral peduncles
Pons: cerebellar peduncles (superior, middle, inferior)
Medulla: inferior olivary nuclei, pyramidal decussation
What are peduncles?
Large white matter tracts
How is the pins attached to the cerebellum?
Via the cerebellar peduncles
What is the tectum?
The roof of the brainstem
Part of the midbrain
What is the tegmentum?
Stucutre that is continuous with the spinal cord
What are the important features of the tectum?
Inferior and superior colliculi
What are the important features of the tegmentum?
Cranial nerve nuclei
Reticular formation
What is the basis in the brainstem?
What is it important for?
Basilar pons
Important for descending motor control
Describe the functional divisions of the brainstem?
Ventral: motor control
Dorsal: cranial nerves and their regulation
Decsribe the proportion of tectum, tegmentum and basis at each level of the brainstem?
Blue - tectum; Green - tegmentum; Red - basilar part
From superior to inferior: mibrain, pons, medulla
Describe the way in which the cranial nerves exit the cranium?
CN III-XII exit brainstem in order, rostral to caudally
Most exit ventral surface, except CN IV
Describe the rule of four for the cranial nerves?
4 CN exit the medulla (CNIX-XII)
4 CN exit the pons (CNV-VIII)
4 CN exit above the pons (2 in the midbrain- CNIII&IV)
Where do sensory nuclei of the cranial nevres develop from? Where do motor nuclei develop from?
Sensory: alar plate
Motor: basal plate
How are the cranial nerve nuclei organised within the brainstem?
Positioned in columns (6 either side of midline)
Grouped based on similar functions
Motor nuclei - midline
Sensory nuclei - lateral
What are the three motor and three sensory columns for cranial nerve nuclei that lie within the brainstem?
MOTOR: general somatic motor, branchial motor, general visceral
SENSORY: general and special visceral, general somatic, special somatic
Within which structure is the reticular formation found?
Tegmentum
What is the reticular formation continuous with rostrally and caudally?
Rostrally: nuclei in the thalamus
Caudally: intermediate grey matter of spinal cord
What are the functions of the rostral and caudal elements of the reticular formation?
Rostral (midbrain and upper pons): maintain alert conscious state
Caudal (pons and medulla): motor reflex and autonomic functions
What is the ascending reticular activating system?
Rostral element of the reticular formation
Long projection systems that modulate forebrain activity
At which levels of the brainstem is the reticular formation found?
All levels
What are the two major ascending pathways that traverse the brainstem?
Dorsal column-medial lemniscus system
Anterolateral system
What is the major descending pathway that traverses the brainstem?
Corticospinal tract
What do the dorsal aspects of the brainstem contain? What do the ventral spects contain?
Dorsal: cranial nerve nuclei, reticular formation
Ventral: structures associated with descending motor tracts
