CBNS 116 Lecture 7 - Brainstem I: Organization, key landmarks and cross sections
Lecture notes by Todd Fiacco
Read Nolte Chapter 11: “Organization of the brainstem”.
FOR NEXT LECTURE: Begin reading Nolte Chapter 12: “Cranial nerves and their nuclei”.
Although the material in these chapters is challenging, aside from part of Chapter 23 on the
hypothalamus and pituitary, they are the only 2 chapters assigned during the middle third of
the course so you will have extra time to study the material.
The big picture:
is the most caudal part of the brain and is a very important
transitional structure situated between the spinal cord caudally and the
rostrally. In some ways it resembles the spinal cord, but the clear-cut
organization of the spinal cord with the white matter on the outside and the gray matter on the
inside is lost in the brainstem. For example, rather than having continuous columns of cells
(such as Clarke’s column and intermediolateral cell column), the gray matter of the brainstem
is discontinuous, forming distinct nuclei.
The brainstem can be thought of as the “heart” of the central nervous system. Although the
brainstem is the most evolutionarily ancient brain region, it is the most important in terms of
survival. This is because the brainstem contains centers regulating attention, alertness, and
sleep (consciousness), respiratory control, cardiovascular control, pain modulatory control, as
well as ingestion, defecation, and urination. It also contains all of the fiber pathways by which
the cerebellum communicates with the spinal cord and brain. In addition, the brainstem is
home to modulatory neurotransmitter systems that project to all other brain areas, and also
contains nuclei of all cranial nerves with the exception of olfactory (I) and optic (II) (although it
contains an important structure involved in visual orientation, the superior colliculus). Thus the
brainstem is an important control center for eye movements (CNs III, IV, VI) and autonomic
control of heart rate and blood pressure (CNs IX, X). Via the cranial nerves, the brainstem is
the spinal cord equivalent of somatosensory, autonomic, and motor control of the head, while
also subserving the special senses of hearing, equilibrium, and taste. Based on this host of
important functions, it is easy to surmise that even small lesions occurring in the brainstem
can have devastating consequences.