The Brainstem

Abstract

Overview of Brainstem Functions The brainstem serves numerous crucial neurologic functions. The most clinically relevant functions include: 1. Home of nuclei that project axons through cranial nerves 3-12. Cranial nerve 1 (Olfactory nerve) directly synapses with cortex. Cranial nerve 2 (Optic nerve) synapses in the lateral geniculate nucleus of the thalamus, which then projects to primary visual cortex. 2. Transmission of information via axons from the cortex to the spinal cord (e.g. corticospinal tract), from hypothalamus to the spinal cord (descending first-order sympathetic neurons) and from the spinal cord to the thalamus and cortex (e.g. dorsal column-medial lemniscus system and spinothalamic tract). 3. Transmission of information via axons from the cortex to the cerebellum (corticopontocerebellar fibers), from the spinal cord to the cerebellum (e.g. dorsal, cuneo, ventral, and rostral spinocerebellar tracts), and from the cerebellum to the thalamus and cortex (brachium conjunctivum). 4. Transmission of information via axons between cranial nerves (e.g. medial longitudinal fasciculus) Other brainstem functions that will not be discussed include: 1. Home of nuclei that project axons to the spinal cord (e.g. red nucleus and the rubrospinal tract, etc). 2. Home of nuclei that project to the cerebellum (inferior olive) 3. Home of nuclei that modulate cortical/diencephalic/cerebellar/brainstem activity (e.g. raphe nucleus, etc) 4. Home of nuclei that modulate cranial nerve nucleus activity (e.g. paramedian pontine reticular formation) 5. Home of relay nuclei (e.g. superior olive, inferior colliculus, etc.)