Brainstem

The brain is subdivided into 2 - name them

Prosencephalon (Forebrain)

Rhombencephalon (Hindbrain)

What does the Prosencephalon (Forebrain) consist of

What does the Rhombencephalon (Hindbrain) consist of

Brainstem is : 

What is the clinical meaning of “bulb” in the context of the brainstem?

Refers to the medulla; related to “bulbar palsy.”

Which major tract passes through the brainstem and connects motor cortex to cranial nerve nuclei?

Corticonuclear tracts.

Brainstem has a vital role in what

basic attention, arousal, and consciousness

Brainstem passes info between what

Pass information between the spinal cord and cerebrum

Green dots = nerves - roman numerals

CP=cerebral peduncle

Pyr= pyramid

SCP=superior cerebellar peduncle

ICP=inferior cerebellar peduncle

MCP=middle cerebellar peduncle

Midbrain is aka  

Mesencephalon

How long is the midbrain?

Approximately 2 cm

Which narrow channel passes through (transverses) the midbrain? What does it carry?

The cerebral aqueduct; carries cerebrospinal fluid (CSF).

The midbrain connects what structures in the brain

Connects pons and cerebellum with forebrain

What is the interpeduncular fossa

A deep midline depression between the cerebral peduncles

Why does the interpeduncular fossa have a perforated appearance

Small blood vessels perforate its floor

Which cranial nerve emerges from the groove on the medial side of the cerebral peduncle

The oculomotor nerve (CN III).

What are the superior and inferior colliculi collectively called?

The corpora quadrigemina.

What is the function of the superior colliculi?

Visual reflex centers.

What is the function of the inferior colliculi?

Auditory relay centers.

Which cranial nerve emerges just below the inferior colliculi?

The trochlear nerve (CN IV).

What are the three main parts of the midbrain?

Crus cerebri (anterior), tegmentum (posterior), and tectum (posterior to the aqueduct).

What structure divides the cerebral peduncles into anterior and posterior parts?

The substantia nigra.

Which tracts descend through the crus cerebri?

Descending axonal tracts

What lines the cerebral aqueduct

Ependymal cells

What surrounds the cerebral aqueduct?

Central gray matter (periaqueductal gray).

What is the superior colliculus composed of?

A large nucleus of gray matter

From where does the superior colliculus receive afferent fibers

Corticotectal fibers from the visual cortex of the occipital lobe.

The frontal eye fields of the frontal lobe.

What function does the superior colliculus control?

Eye movement

Describe the red nucleus & its location

Gray matter mass between Cerebral aqueduct and Substantia nigra

What gives the red nucleus its reddish hue

An iron-containing pigment in the cytoplasm of its neurons.

Which tract originates from the red nucleus and what is its function

The rubrospinal tract; involved in motor control.

What type of structure is the inferior colliculus

A nucleus of gray matter.

What type of information does the inferior colliculus receive?

Auditory information (afferent auditory fibers).

The inferior colliculi gets afferent fibres in and leaves efferent fibres out. Where do the fibres project

Afferent auditory fibre → inferior colliculus → efferent fibres → thalamus → auditory cortex of temporal lobe

Internal structure of midbrain

Where is the substantia nigra located?

Between the crus cerebri and the tegmentum.

What type of neurons are found in the substantia nigra?

Dopaminergic neurons.

What pigment is found in substantia nigra neurons?

Melanin - found in cytoplasm of neurons

What is the functional role of the substantia nigra?

Regulation of muscle tone

Damage to the substantia nigra is associated with which disease?

Parkinson’s disease.

Which midbrain levels is the substantia nigra in

All midbrain levels

Internal structure of midbrain

What is the reticular formation?

A complex mass of neurons spread throughout the brainstem, forming many nuclei

What is the role of the rostral reticular formation (midbrain and upper pons)?

Maintains an alert, conscious state.

What is the role of the caudal reticular formation (pons and medulla)?

Motor, reflex, and autonomic functions.

What is the extent of the reticular formation

From the spinal cord → medulla → pons → midbrain → diencephalon

How is the reticular formation organized?

Into three longitudinal columns:

• Median raphe nuclei

• Paramedian reticular formation

• Lateral reticular formation

What is the function of raphe nuclei

Sleep regulation

Where is the pons located relative to the cerebellum?

Anterior to the cerebellum.

Which structures does the pons connect?

Connects medulla to midbrain.

Pons nuclei and tracts relay information to and from what

the cerebellum

Which cranial nerve nuclei are found in the pons?

Sensory & motor nuclei for CN V (trigeminal), CN VI (abducens), CN VII (facial), CN VIII (vestibulocochlear)

Which physiological process do pontine nuclei help regulate?

Respiration

What types of tracts (ascending/descending…) pass through the pons?

Ascending, descending, and transverse tracts.

What is the main feature of the anterior surface of the pons?

Many transverse fibers converging on each side to form the middle cerebellar peduncle.

What shallow groove runs in the midline of the anterior surface of the pons?

The basilar groove.

Which cranial nerve emerges from the anterolateral surface of the pons?

The trigeminal nerve (CN V).

Which three cranial nerves emerge at the junction of the pons and medulla?

CN VI (abducens), CN VII (facial), CN VIII (vestibulocochlear).

What hides the posterior surface of the pons from view?

The cerebellum.

What shape does the posterior surface of the pons form?

A triangular shape.

What part of the ventricular system does the posterior pons form?

The upper half of the floor of the 4th ventricle.

What structure divides the posterior surface of the pons symmetrically?

The median sulcus.

What is the facial colliculus

An expanded inferior medial eminence

What are the two main parts of the pons?

Posterior = Tegmentum

Anterior = Basal part.

What nuclei are found in the basal part of the pons

Pontine nuclei.

What fibers pass through the pontine nuclei & what pathway are they a part of

Transverse pontocerebellar fibers

Part of the corticopontocerebellar pathway

Which structures does the medulla oblongata connect?

Pons (above) and spinal cord (below).

What types of autonomic nuclei are found in the medulla (oblongata)?

Autonomic nuclei that control visceral activities (reflex centers)

Cardiovascular centers (cardiac and vasomotor centers).

Respiratory rhythmicity centers.

What groove runs along the anterior midline of the medulla?

The anterior median fissure (continuous with the fissure of the spinal cord).

What structures are found on either side of the anterior median fissure?

The pyramids (containing corticospinal fibers)

Decussation of the pyramids at the superior/inferior part of the pyramids?

Inferior

What structures lie posterolateral to the pyramids & what do these structures contain?

The olives, which contain the inferior olivary nucleus.

Which cranial nerve emerges between the olive and pyramid

Hypoglossal nerve

Which cranial nerves emerge posterior to the olives

Glossopharyngeal (CN IX), Vagus (CN X), and Accessory (CN XI).

Which cerebellar peduncle is found posterior to the olives?

 The inferior cerebellar peduncle.

What does the superior half of the posterior medulla form

The lower part of the floor of the 4th ventricle.

What does the inferior half of the posterior medulla continue as?

The spinal cord.

What structures are found on either side of the posterior median sulcus

Gracile tubercle (containing gracile nucleus).

Cuneate tubercle (containing cuneate nucleus) lateral to gracile

What do the pyramids contain?

The pyramidal tracts (corticospinal fibers).

What forms the olives

The inferior olivary nuclei.