What are the functions of the brainstem?
–Allows ascending and descending pathways to reach thalamus and cerebellum from spinal cord
–Cardiovascular, respiratory and consicousness (reticular formation)
–Head’s equivalent to spinal nerves
–Also sight, hearing, equilibrium and gustation
–Cranial nerve nuclei
What are the boundaries of the brainstem?
Caudally – Medulla is continuous with the spinal cord at level of the foramen magnum
Rostrally – Midbrain is continuous with the diencephalon (thalamus, hypothalamus etc)
Ventrally – Clivus of occipital bone
Dorsally – Cerebellum
Which compenents of the ventricular system run through the brainstem?
Fourth ventricle and cerebral aquaduct
How many of the 12 cranial nerves arise from the brain stem?
From which of the primary brain vesicles is the most of brainstem derived excluding the midbrain (but including the cerebellum)?
From which of the primary vesicles is the midbrain derived?
What kind of fibres do the pyramids (medulla) contain?
Descending motor fibres.
What is the name of the groove that seperates the pons and medulla and what happens there?
The pontomedullary sulcus - basilar artery is formed here.
Which cranial nerve comes off at the groove between the pyramid and olive and what is its function?
CNXII (12) - hypoglossal. Motor nerve to tongue.
What is the name of the space between the cerebral peducles and which cranial nerve is given off here (ventral)?
Interpeduncular fossa - CNIII (3) - oculomotor nerve.
Which part of the brainstem is attached to the middle cerebellar peduncle?
Which part of the brainstem is attached to the inferior cerebellar peduncle?
Which part of the brainstem connects to the superior cerebellar peduncle?
What are the gross divisions of the dorsal brainstem?
Superior and inferior colliculi
Which is the only cranial nerve to come off the dorsal aspect of the brainstem, directly inferior to the inferior colliculus, and what does it do?
CNIV (4) - trochlear - controls one of the six mucles that move the eye.
What is a fascicle?
A tract of white matter.
What sort of information runs through the gracile or cuneate fasicles of the medulla oblongata?
Specific pinpoint touch and proprioception.
What lies at the most superior part of the dorsal aspect of the medulla oblongata?
The cuneate and gracile nuclei
What is the reticular formation?
Within the tegmentum of the brainstem is a complex, multisynaptic network of neurons – the reticular formation.
What are the components of the reticular formation and what are its functions?
•Reticular nuclei – give rise to a descending motor pathway (reticulospinal tract, see Term 3)
•Vital autonomic centres – eg. respiratory, cardiovascular
•Cells giving rise to Ascending Reticular Activating System – pass to the cortex and involved in consciousness (damage = coma)
•Sleep wake cycle
What are the three areas of the brainstem that can be identified in crossection?
Tectum (most dorsal), tegementum, and basal.
Which is the only region of the brainstem to have a substantial tectum?
Midbrain - superior and inferior colliculi
What structures would be found within the tegmentum?
Contains cranial nerve nuclei and tract, reticular formation and some ascending/descending pathways.
What structures are found within the basal part?
Descending fibres from cerebral cortex (pyramids, cerebral peduncles).