brainstem

yellow

midbrain

blue

pons

purple

medulla oblongata

6 main jobs of the brainstem

Connect → Passageway → Cranial nerves → Cerebellum → Nuclei → Survival

What does the brainstem connect

The cerebrum to the spinal cord

What travels (pathway) through the brainstem?

All ascending and descending pathways/tracts

Which cranial nerve nuclei are NOT in the brainstem?

Cranial nerves I and II (olfaction/smell and vision).

What does the brainstem connect to the cerebellum?

The rest of the CNS and PNS

What are 3 important nuclei found in the brainstem?

Substantia nigra, red nucleus, and reticular formation.

Which brainstem structure is associated with consciousness?

Reticular formation

What basic survival functions does the brainstem control?

Cardiac function, respiratory function, sleep, hunger, and thirst

The midbrain is the _________ part of the brainstem, about _____ cm long.

smallest; 1.5

Midbrain=

Size + Functions + Connections + Tectum + Sight + Hearing + CN III

What is the smallest (size) part of the brainstem?

The midbrain

What functions are associated with the midbrain?

Visual responses, gustatory functions, and coordination of movement

Midbrain Importartant Structures:

Crus cerebri → Tectum → Superior (sight) → Inferior (hearing) → Cranial nerve III

What do the paired crus cerebri do?

Connect the cerebrum with the rest of the CNS and PNS through the cerebral peduncles.

Where is the tectum located?

On the dorsal (back) surface of the midbrain

What does the tectum contain?

The quadrigeminal bodies

What do the superior colliculi control?

Visual responses

What do the inferior colliculi control?

Auditory responses

Which cranial nerve has nuclei in the midbrain?

Cranial nerve III (oculomotor nerve)

What is the memory trick for the colliculi?

Superior = sight; inferior = hearing

The NUCLEI found in the midbrain are:

• Medial geniculate body

• Substantia nigra

• Superior colliculus

• Inferior colliculus

• Red nucleus

• Oculomotor nucleus (CN III)

• Edinger-Westphal nucleus (CN III)

Medial geniculate body (nuclei)

Auditory relay. Processes and relays hearing information

Substantia nigra (nuclei)

Supplies dopamine to the basal ganglia

Superior colliculus (nuclei)

Visual relay. Helps locate visual stimuli.

Inferior colliculus (nuclei)

Auditory relay. Helps locate sounds in space

Red nucleus (nuclei)

Motor coordination; part of the extrapyramidal pathway

Oculomotor nucleus (III) (nuclei)

Controls muscles that move the eye and lift the upper eyelid

Edinger–Westphal nucleus (III) (nuclei)

Controls the sphincter muscle of the iris

The TRACKS Found in the Midbrain are:

1. Corticospinal tract

2. Corticobulbar tract

3. Temporopontine fibers

4. Frontopontine fibers

5. Medial longitudinal fasciculus

6. Medial lemniscus

7. Spinothalamic tract (anterolateral and ventrolateral)

8. Trigeminal lemniscus

Corticospinal tract (track)

Motor efferent from cerebral cortex to spinal nerve nuclei

Corticobulbar tract (track)

Motor efferent from cerebral cortex to brainstem cranial nerve nuclei

Temporopontine fibers (track)

Fibers from the temporal lobe that terminate in the pontine nuclei

Frontopontine fibers (track)

Fibers arising from frontal lobe, passing through cerebral peduncle and terminating in pons

Medial longitudinal fasciculus (MLF) (track)

Coordinates eye movements with head movements; helps generate the vestibulo-ocular reflex; connects cranial nerves III, IV, and VI and interacts with cranial nerve VIII.

Medial lemniscus (track)

Carries sensory information from the gracile and cuneate nuclei in the medulla to the thalamus

Spinothalamic tract (anterolateral and ventrolateral) (track)

Carries touch, pain, and temperature information to the thalamus.

Trigeminal lemniscus (track)

Carries pain, touch, and temperature information from the face to the ventral posteromedial (VPM) nucleus of the thalamus

Latin for “bridge”

Pons

Pons cranial nerve nuclei =

Cranial nerves IV, V, VI, and VII.

Pons cerebellar peduncles =

Superior and middle cerebellar peduncles

Originates in the midbrain

Superior cerebellar peduncle

Cerebellopontine angle =

Junction where the cerebellum meets the pons

Tumors at the cerebellopontine angle = vestibular function

Can affect balance

Tumors at the cerebellopontine angle= auditory function

hearing

Tumors at the cerebellopontine angle =

Can affect balance (vestibular function) and hearing (auditory function).

Nuclei of the Pons ARE:

• Principal motor nucleus of trigeminal nerve (V)

• Principal (pontine) sensory nucleus of trigeminal nerve (V)

• Mesencephalic nucleus of trigeminal nerve (V)

• Abducens nucleus (VI)

• Facial nucleus (VII)

• Nucleus of trochlear nerve (IV)

• Cochlear nuclei (anteroventral, dorsal, posteroventral)

• Vestibular nuclei

• Superior olivary complex

• Periolivary nuclei

Principal motor nucleus of trigeminal nerve (V) (nuclei)

Controls chewing muscles

Principal sensory nucleus of trigeminal nerve (V) (nuclei)

Feeling in the face and scalp

Mesencephalic nucleus of trigeminal nerve (V) (nuclei)

Senses the position of chewing muscles (proprioception)

Abducens nucleus (VI) (nuclei)

Moves the eye outward

Facial nucleus (VII) (nuclei)

Controls facial expressions

Nucleus of trochlear nerve (IV) (nuclei)

Helps move the eye downward using the superior oblique muscle

Cochlear nuclei (nuclei)

Process hearing information

Vestibular nuclei (nuclei)

Control balance and orientation in space

Superior olivary complex (nuclei)

Helps locate where sounds come from

Periolivary nuclei (nuclei)

Help send signals that adjust hearing sensitivity and protect the auditory system.

Tracts Found in the Pons ARE

• Superior cerebellar peduncle

• Anterior (ventral) spinocerebellar tract

• Posterior (dorsal) spinocerebellar tract

• Medial longitudinal fasciculus (MLF)

• Tectospinal tract

• Lateral lemniscus

• Middle cerebellar peduncle

• Pontocerebellar fibers

• Corticopontine fibers

• Corticospinal tract

Superior cerebellar peduncle (Tract)

Carries information out of the cerebellum toward the thalamus and red nucleus

Anterior (ventral) spinocerebellar tract (Tract)

Carries information about lower-body movement to the cerebellum.

Posterior (dorsal) spinocerebellar tract (Tract)

Carries information about muscle position and movement from the lower body to the cerebellum

Medial longitudinal fasciculus (MLF) (Tract)

Coordinates eye movements with head movements.

Tectospinal tract (Tract)

Helps coordinate head and neck movements in response to visual and auditory stimuli.

Lateral lemniscus (Tract)

Carries hearing information toward the midbrain.

Middle cerebellar peduncle (Tract)

Carries information from the pons to the cerebellum.

Pontocerebellar fibers(Tract)

Carry information from the pons to the cerebellum.

Corticopontine fibers(Tract)

Carry movement plans from the cerebral cortex to the pons.

Corticospinal tract(Tract)

Carries movement commands from the cerebral cortex to the spinal cord.

Corticobulbar tract (Tract)

Carries movement commands from the cerebral cortex to cranial nerve nuclei.

Important Structures and Landmarks of the Medulla Oblongata:

1. Anterior median fissure

1. Pyramids

2. Pyramidal decussation

3. Ventrolateral sulcus

4. Dorsolateral sulcus

5. Nucleus solitarius (CN X)

6. Nucleus ambiguus (CN IX, X, XI)

7. Hypoglossal nucleus (CN XII)

8. Olive (inferior olivary nuclear complex)

9. Reticular formation

10. Nuclei associated with respiration, blood pressure, and wakefulness

11. Fasciculus gracilis

12. Fasciculus cuneatus

13. Inferior cerebellar peduncle

Medulla oblongata — Anterior median fissure =

Groove that continues from the spinal cord between the pyramids.

Medulla oblongata — Pyramids =

Contain descending motor fibers from the corticospinal tract.

Medulla oblongata — Pyramidal decussation =

Where most corticospinal motor fibers cross to the opposite side in the lower medulla.

Medulla oblongata — Ventrolateral and dorsolateral sulci =

Grooves where cranial nerves IX, X, XI, and XII exit the medulla.

Medulla oblongata — Nucleus solitarius (CN X) =

Processes sensory information, including information from internal organs.

Medulla oblongata — Nucleus ambiguus (CN IX, X, XI) =

Controls muscles involved in swallowing and speaking.

Medulla oblongata — Hypoglossal nucleus (CN XII) =

Controls tongue movements.

Medulla oblongata — Olive (inferior olivary nuclear complex) =

inferior olivary nuclear complex

Relays motor and proprioceptive information to the cerebellum.

between the ventrolateral and dorsolateral sulci

olive

Medulla oblongata — Reticular formation =

Helps regulate alertness and other body functions; extends through the brainstem.

Medulla oblongata — Medullary nuclei =

Help regulate breathing, blood pressure, and wakefulness.

Medulla oblongata — Fasciculus gracilis =

Carries touch, vibration, and body-position information from the lower body.

Medulla oblongata — Fasciculus cuneatus =

Carries touch, vibration, and body-position information from the upper body.

Medulla oblongata — Inferior cerebellar peduncle =

Carries information between the medulla and cerebellum.

Medulla oblongata NUCLEI

1. Cuneate nucleus

2. Gracile nucleus

3. Inferior olivary nucleus (cerebellum)

4. Hypoglossal nucleus (XII)

5. Nucleus ambiguus (IX, X, XI)

6. Spinal nucleus of trigeminal (V)

7. Dorsal motor nucleus of vagus (X)

8. Vestibular nuclei (VIII)

9. Nucleus solitarius (VII, IX, X)

10. Superior and inferior salivatory nuclei (VII, IX)

11. Lateral reticular nucleus

Cuneate nucleus

Receives fine touch and proprioception information from the upper body

Gracile nucleus

Receives kinesthetic and light-touch information from the lower body.

Inferior olivary nucleus

Sends information to the cerebellum to help coordinate and learn movements

Hypoglossal nucleus (CN XII)

Controls tongue muscles for tongue movement.

Nucleus ambiguus (CN IX, X, XI)

Controls muscles involved in swallowing and phonation, including muscles of the pharynx and larynx

Spinal nucleus of the trigeminal nerve (CN V)

Processes pain, touch, and temperature sensations from the face.

Dorsal motor nucleus of the vagus (CN X)

Provides parasympathetic control of organs in the chest and abdomen.

Vestibular nuclei (CN VIII)

Help maintain balance and coordinate head and eye movements.

Nucleus solitarius (CN VII, IX, X)

Receives taste information and visceral sensory information; helps regulate reflexes and autonomic functions.

Inferior salivatory nucleus (CN IX)

Helps control salivary gland secretion.

Superior salivatory nucleus (CN VII)

Helps control salivary and lacrimal (tear) gland secretion.

Lateral reticular nucleus

Part of the reticular formation; helps coordinate motor activity and movement

Tracts Found Within the Medulla

1. Inferior cerebellar peduncle

2. Posterior spinocerebellar tract

3. Anterior spinocerebellar tract

4. Spinal lemniscus (spinothalamic tract)

5. Medial longitudinal fasciculus

6. Trigeminothalamic tract (spinal tract of V trigeminal)

7. Medial lemniscus

8. Fasciculus gracilis

9. Fasciculus cuneatus

10. Pyramidal decussation

11. Lateral corticospinal tract

12. Anterior corticospinal tract

13. Decussation of lemnisci

14. Lateral spinothalamic tract

15. Spinotectal tract

16. Rubrospinal tract

17. Tectospinal tract

18. Tractus solitarius