Brainstem and Reticular Formation

Unit 7

3 major portions of the brainstem

1. midbrain
2. pons
3. medulla

parts of the Midbrain

* crus cerebri
* substantia nigra
* red nucleus
* superior colliculus
* inferior colliculus
* sylvian aqueduct

parts of the Pons

* pontine nuclei
* 4th ventricle
* reticular formation

parts of the medulla

* vestibular nuclei
* olives
* nucleus cuneatus
* nucleus gracillis
* central canal
* reticular formation

crus cerebri

anterior white matter of the cerebral peduncles

substantia nigra

* basal ganglia structure
* role is reward and movement
* part of extrapyramidal motor system

What are the divisions of the substantia nigra

1. pars compacta - output to basal ganglia circuit
2. pars reticulata - input from basal ganglia to other brain structures

red nucleus

* involved in motor coordination
* present in the tegmentum of the midbrain
* part of the extrapyramidal motor system

pontine nuclei

* AKA griseum pontis
* receives motor fibers from the primary motor cortex
* sends information to the contralateral cerebellum via the **middle** cerebellar peduncle
* important for motor learning

reticular formation

* network of nerve pathways that connect the spinal cord, cerebrum and cerebellum
* mediates overall conciousness

vestibular nuclei

CN nuclei for the vestibular nerves

Olives

* nucleus of the pathway between the ==cerebellum and pons== via **inferior** cerebellar peduncle
* involved in motor learning
* degeneration is associated with ==progressive suprenuclear palsy (PSP)==

closed portion of the medulla continuous with

spinal column

open portion of the medulla continuous with

central canal expands to 4th ventricle

obex of medulla continuous with

portion where 4th ventricle narrows to form central canal

What is the anterior median fissure of the medulla interrupted by?

pyramids

what forms the olives

column posterior to the hypoglossal rootlets enlarge to form the olives

where does the vagus nerve emerge from the olive?

shallow groove posterior to olive

what are the exterior landmarks of the nucleus gracilis and cuneatus

gracile and cuneate tubercle

Lesions of the vestibular nuclei can cause?

vertigo, disequilibrium, nystagmus

Vestibular nuclei

makes up the vestibular area, conveys sensory information about the head-orientation and head-motion form receptors in inner ear

Facial collilculus is created when…?

the fibers of CN 7 as it loops around CN 6

Why is the pons known as a bridge?

it is between hemispheres

where do pontine fibers descend?

cerebral peduncles

synapse