Brainstem Flashcards
What are the three broad functions of the brainstem?
- Conduit
- Cranial nerve
- Integrative
How is the brainstem a conduit?
Information goes to the cortex and spinal cord thru the brainstem (white matter tracts)
What are the integrative functions of the brainstem?
Complex motor patterns, cardiorespiratory control, reflexes
Mostly through reticular formation
What are the three main anatomical subdivisions of the brainstem?
- Medulla
- Pons
- Midbrain
In the brainstem, where is the corticospinal tract?
Anterior portion
In the brainstem, where is the spinothalamic tract?
Anterolateral
In the brainstem, where is the medial leminscus?
Varies in location
Where is the tegmentum located in each section of the brainstem?
Medulla: Posterior
Pons: Posterior
Midbrain: Middle
Where is the tectum located in each part of the brainstem?
It is posterior to the ventricle in the pons and midbrain
What consists of the stuff added to the tectum and tegmentum in each section?
Medulla: Olive and pyramid
Pons: Pons
Midbrain: cerebral peduncles
What are some major external features in the medulla?
Anterior: Pyramids, pyramidal decusation, olive (anterolateral)
Posterior: Obex, cuneate and gracile tubercles
CN: IX, X, XII
What are some external features of the pons?
Anterior: Basal pons
Posterior: Middle, inferior, and superior cerebellar peduncle
CN: VII, VIII
What are some external features of the midbrain?
Anterior: Cerebral peduncles
Posterior: Cerebral aqueduct, superior colliculus, inferior colliculus, inferior brachium
CN: III, IV
What are some distinct features of the caudal medulla?
- Clear central canal of grey matter
- Pyramidal decussation at anterior
- NO 4th ventricle
What are distinctive features of the rostral medulla?
- Visible 4th ventricle in the posterior
- Olive with inferior olivary nuclei
- Hypoglossal nucleus
- space between two pyramids
What are some distinctive features of the caudal pons?
- Large 4th ventricle in the posterior
- attached to cerebellum by middle cerebellar peduncle
- inferior cerebellar peduncle is visible
What indicates middle pons vs. caudal pons?
Middle pons has larger superior cerebellar peduncle and no inferior cerebellar peduncle
What are some distinct features of the rostral pons?
Looks like alien brain
- 4th ventricle is much smaller than caudal
- Lots of white matter in the pons including corticospinal tract
What are some distinctive features of the caudal midbrain?
- Heavily stained decusation of the superior cerebellar peduncle right in the middle just anterior to the aqueduct
- Inferior colliculus on posterolateral aspects
- CN IV seperated from the rest of the structure laterally
What are some distinctive features of the rostral midbrain?
- cerebral peduncles very lateral with large anterior space between them
- CN III in the middle of the structure
- substantia Nigra between the cerebral peduncles and the superior cerebellar peduncles
What are the four types of axons in spinal nerves?
Somatic sensory: pain, temp., mechanorecepters
Visceral sensory: GI tract, blood vessels
Visceral motor: preganglionic autonomic
Somatic motor: innervate skeletal muscle
How are the types of cranial nerve nuclei arranged in the brainstem?
Posterolateral to anteromedial
SS, VS, VM, SM
What is different about the nuclear arrangement in the brainstem than in the spinal cord?
Not all columns are in all levels, and some are discontinuous
Along with somatic sensory, visceral sensory, visceral motor, and somatic motor, what are the two other possible functions of cranial nerves?
Special sensory: hearing, equilibrium
Brachial motor: innervate muscles derived from pharyngeal arches (larynx, pharynx, jaw, face)
*No cranial nerve has all 6
What is the name, type, and function of cranial nerve I?
Olfactory
Special Sensory afferent
Smell
CN II?
Optic
Special sensory afferent
Vision
CN III?
Oculomotor
General sensory efferent, general visceral efferent
Eye movement, pupil constriction and accommodation (focus)
CN IV?
Trochlear
General sensory efferent
Eye movement
CN V?
Trigeminal
General sensory afferent, Special visceral efferent
Head and neck sensation, motor for muscles of mastication
CN VI?
Abducens
General sensory efferent
Eye movement
CN VII?
Facial
General sensory afferent, Special sensory afferent,
Special visceral efferent,
General visceral efferent
Sense around ear, taste, facial expression, secretomotor
CN VIII?
Vestibulocochlear
Special sensory afferent
Hearing and balance
CN IX?
Glossopharyngeal
Special Visceral efferent, General visceral efferent,
General visceral afferent,
General sensory afferent,
Special sensory afferent
Stylopharyngeus, secretomotor, carotid body and sinus, part of tongue, taste
CN X?
Vagus
Special visceral efferent,
General visceral efferent,
Special sensory afferent,
General sensory afferent
Pharynx/larynx muscles and glands, stretch and chemoreceptors in aorta, skin on back of ear
CN XI?
Accessory
Special visceral efferent
Sternomastoid and trapezius
CN XII?
Hypoglossal
General sensory efferent
Tongue
From where does the blood supply come from for the brainstem?
Two caudal vertebral arteries come together to form basilar artery
These vertebral arteries, the basilar artery and its perforating branches supply the brainstem
What arteries supply the lateral brainstem?
Circumferential arteries
