Brainstem Anatomy

Brainstem Functions

Vegetative (circulation, respiration, digestion, sleep/wake), rhythmic and crude motor control

Brainstem components

Cranial nerves and nuclei (head and neck sensory and motor functions), Ascending and descending pathways (forebrain to and from spinal cord; input and output from cerebellum)

Main divisions of the brainstem

medulla, pons, midbrain

Medulla location

rostral to the spinal cord and caudal to the pons

Parts of the medulla

pyramids, inferior olives (inferior olivary nuclei), central canal

Medulla pyramids location

ventral surface of the brainstem, just to either side of the midline

Medulla Pyramids function

contain motor axons of the corticospinal tract

Pyramidal Decussation

At caudal medulla, some axons in the corticospinal tract cross to the contralateral side

Inferior olives location

on the ventral surface of the brainstem, just later to the pyramids

Inferior Olives function

provide afferent input to the cerebellum

Central canal function

CSF circulation in the spinal cord and medulla

Pons location

rostral to the medulla and caudal to the midbrain

Parts of the pons

cerebellar peduncles, pontine nuclei, fourth ventricle, fibers of the corticospoinal tract

Cerebellar peduncles

axons relaying information into and out of the cerebellum

Pontine nuclei

clusters of neurons found among corticospinal axons within the pons; convey motor information from the cortex to the cerebellum

Fourth ventricle

located between the cerebellum and the brainstem near the level of the pons; part of the ventricular system

Fibers of the corticospinal tract pathwa

descend through the pons on their way to the pyramids

Pons other definition

the bulge of axons running along the ventral side of the pons region

Midbrain location

rostral to the pons

Midbrain components

cerebral peduncles, mammillary bodies, cerebral aqueduct, inferior and superior colliculi

Cerebral peduncles

contains descending motor axons and other fibers

mammillary bodies location

ventral surface of the brainstem

mammillary bodies are associated with the

hypothalamus

Cerebral aqueduct structure

narrow tube containing CSF that runs through the midbrain

Cerebral aqueduct function

Connects the 3rd and 4th ventricles

Inferior colliculi location

located on the dorsal surface of the brainstem

Inferior colliculi function

relay auditory information to the thalamus

Superior colliculi location

on the dorsal surface of the brainstem

Superior colliculi function

relay visual and other sensory information to motor neurons involved in orienting reflexes

Tectum

the colliculi and surrounding regions