Brain Stem & Reticular Formation

Define the three subdivisions of the brainstem

Midbrain

What is the primary conduit function of the brainstem?

Conveys information to and from the cerebrum and spinal cord

What specialized nerves emerge from the brainstem?

Cranial nerves

What are the three broad functions of the brainstem?

Conduit functions

What structure is the central core of the brainstem involved in integrative functions?

Reticular formation

What is the tectum of the brainstem?

Tissue dorsal to the ventricle

What is the tegmentum of the brainstem?

Tissue ventral to the ventricle

What is the basis of the brainstem?

Ventral structures added after neural tube closure

Which brainstem levels contain tectum

tegmentum

Where is the spinothalamic tract located in the brainstem?

Anterolateral

Where is the medial lemniscus located in the brainstem?

More medial but variable

Where is the corticospinal tract located in the brainstem?

Anterior

What surface structures are characteristic of the midbrain?

Cerebral peduncles

What structure connects the third and fourth ventricles in the midbrain?

Cerebral aqueduct

What gray matter surrounds the cerebral aqueduct?

Periaqueductal gray

Which cranial nerve nucleus is found in the rostral midbrain?

Oculomotor nucleus (CN III)

Which colliculus is found in the rostral midbrain?

Superior colliculus

Which cranial nerve nucleus is found in the caudal midbrain?

Trochlear nucleus (CN IV)

Which colliculus is found in the caudal midbrain?

Inferior colliculus

What dopaminergic structure is found in the midbrain?

Substantia nigra

What is the distinguishing ventricular structure of the pons?

Fourth ventricle

What major fiber tract gives the pons its name as a “bridge”?

Cerebellar peduncles

Which cranial nerve nuclei are found in the middle pons?

Trigeminal nerve (CN V)

Which cranial nerve nuclei are found in the caudal pons?

Abducens (CN VI) and Facial (CN VII)

What nucleus in the rostral pons is part of the reticular formation?

Locus ceruleus

What surface features characterize the medulla?

Pyramids

What motor tract forms the pyramids of the medulla?

Corticospinal tract

What sensory nuclei are found in the caudal medulla for the PCML pathway?

Nucleus gracilis and nucleus cuneatus

Where does pyramidal decussation occur?

Caudal medulla

What cranial nerve nucleus is found in the rostral medulla?

Hypoglossal nucleus (CN XII)

What is the inferior olivary nucleus involved in?

[NOT SPECIFIED IN LECTURE]

What artery supplies the medial medulla?

Anterior spinal artery

Which arteries arise from the vertebral arteries before forming the basilar artery?

Anterior spinal artery

What artery supplies the lateral medulla?

Posterior inferior cerebellar artery (PICA)

At what level does the basilar artery bifurcate?

Midbrain

What arteries arise from the basilar artery?

Pontine arteries

What does the posterior cerebral artery supply?

Rostral midbrain and posterior diencephalon

What are the four general functional components of spinal nerves?

GSA

Which two additional functional components are found in the brainstem?

SSA and SVE

How are brainstem nuclei arranged developmentally?

Based on alar and basal plates

What is the reticular formation?

A collection of structures in the central core of the brainstem

Why is the reticular formation difficult to define anatomically?

Diffuse

What are major functions of the reticular formation?

Motor control

What are the three longitudinal zones of the reticular formation?

Raphe nuclei

Which reticular formation zone contains serotonergic nuclei?

Raphe nuclei

Which reticular formation zone is involved in cranial nerve reflexes?

Lateral zone

What is a central pattern generator?

Neuronal circuits generating repetitive motor patterns independent of sensory input

Give examples of behaviors controlled by central pattern generators

Chewing

What tracts mediate reticular formation influence on posture?

Reticulospinal tracts

Where do medial reticulospinal tracts originate and project?

Pons to ipsilateral anterior funiculus

Where do lateral reticulospinal tracts originate and project?

Medulla to bilateral lateral funiculi

What structure is central to pain suppression?

Periaqueductal gray

From where does the PAG receive pain information?

Spinomesencephalic and spinoreticular fibers

To which nucleus does the PAG project for pain modulation?

Nucleus raphe magnus

What neurotransmitter is predominant in raphe nuclei?

Serotonin (5-HT)

What neurotransmitter is predominant in locus ceruleus?

Norepinephrine (NE)

Where is the locus ceruleus located?

Rostral pons near the fourth ventricle

What is the role of the locus ceruleus in behavior?

Attention

What clinical condition is associated with loss of locus ceruleus neurons?

Parkinson’s disease

Where are most dopaminergic neurons located?

Midbrain

Name two dopaminergic nuclei in the midbrain

Substantia nigra pars compacta and ventral tegmental area

What functions are associated with dopamine pathways?

Movement initiation

What system maintains consciousness and arousal?

Ascending reticular activating system

How does the reticular formation differ from precise sensory pathways?

Diffuse projections to multiple regions

What autonomic functions are regulated by the reticular formation?

Respiratory and cardiovascular control