6 - Brainstem

what are the contents of the brainstem?

midbrain, pons, medulla

what does the brainstem connect?

cerebrum superiorly, cerebellum posteriorly, and spinal cord inferiorly

where does pyramidal decussation occur?

right below medulla before becoming spinal cord

brainstem functions

communication between cerebrum, cerebellum and spinal cord

contains cardiovascular, respiratory, vomiting and vasomotor centers

contains passageway for different neural pathways

home to many cranial nerve nuclei

what is another name for the midbrain?

mesencephalon

what is the functional significance of the midbrain?

coordinated eye movements

pupillary light reflex

consciousness and arousal

what are the structures in the midbrain

tectum (roof)
- quadrigeminal plate - superior and inferior colliculi
- cerebral aqueduct - periaqueductal gray

tegmentum
- red nucleus
- reticular formation
- substantia nigra

cerebral peduncles (crus cerebri)

the tectum is ____ to the cerebral aqueduct

dorsal

the quadrigeminal plate has ___ swellings on the ____ part of the midbrain. it contains the ______ and ______.

4, dorsal, superior, inferior

what are the functions of the superior and inferior colliculi?

superior: visual processing (gaze)

inferior: auditory processing

what surrounds the cerebral aqueduct? what does it do?

the periaqueductal gray

is the control center for descending pain modulation

what does the cerebral aqueduct contain? what does it connect? what direction does it go?

CSF

3rd and 4th ventricles

goes vertically

what is the tegmentum? what are its structures?

it is the region between the cerebral peduncles and cerebral aqueduct

contains the red nucleus and reticular formation

what does the red nucleus do? where is it found?

motor coordination in the extra pyramidal system (basal nuclei modulates rather than corticospinal tract)

only present at the same level as superior colliculi, not present at level of inferior colliculi

what is the reticular formation in tegmentum? what does it do?

central core of brainstem where intermingling of axons occurs

mediates level of consciousness

where is the substantia nigra? what is its main pathway? what does it do?

consistent landmark throughout the midbrain (in tegmentum)

dopaminergic pathways

responsible for reward (addiction), learning (cognition), and movement (extra-pyramidal system - basal nuclei)

where are the cerebral peduncles (crus cerebri) located? what does it do?

lateral, under diencephalon, lateral to mammillary bodies

fiber bundle that connects cerebral cortex with spinal cord, pons, and brainstem

what are the tracts in the midbrain?

corticospinal tract, spinothalamic tract, dorsal column - medial lemniscus tract

where are the tracts in the midbrain located?

green - corticospinal

red - spinothalamic

blue - dorsal column - medial lemniscus

what are the cranial nerves in the midbrain?

CN III - oculomotor

CN IV - trochlear

where are the pons located?

anterior to cerebellum and IV ventricle

inferior to midbrain

superior to medulla

what is the functional significance of pons?

reflex control, respiratory system

eye movements and coordinated movements in eye and head

corneal reflex

what are structures in the pons?

middle cerebellar peduncle, 4th ventricle, reticular formation

where is the reticular formation located?

between pons proper (bulge) and 4th ventricle

what are the neural pathways in the pons?

dorsal column - medial lemniscus tract

corticospinal tract

spinothalamic tract

what are the cranial nerves in the pons?

CN V: trigeminal

CN VI: abducens

CN VII: facial

CN VIII: vestibulocochlear

where is the medulla located?

inferior to the pons and superior to the spinal cord

what is the functional significance of the medulla?

reflex control of CV and respiratory systems

reflex control of swallowing and vomiting

important in phonation (control of tongue, larynx, pharynx)

what are the structures in the medulla?

pyramid

olive
- inferior olivary nucleus

4th ventricle

reticular formation

what tracts are in the medulla?

corticospinal tract

spinothalamic tract (ALS system)

dorsal column medial lemniscus

where does the dorsal column cross?

crosses at internal arcuate fibers, not at pyramid decussation or anterior white commissure

what does the pyramid of medulla contain? where does it travel?

contains corticospinal tract (majority of corticospinal fibers cross to form lateral corticospinal tract but some stay ipsilateral as anterior corticospinal tract)

courses inferiorly to the pyramidal decussation

where is the olive of medulla? what does it contain?

paired anterolateral bulges lateral to pyramids

contains olivary nucleus, neurons in the olive are related to the cerebellum that is constant getting proprioceptive and motor input. olivary fibers are one kind of input

what are the cranial nerves in the medulla?

CN IX: glossopharyngeal

CN X: vagus

CN XI: accessory

CN XII: hypoglossal

what is the central canal in the medulla?

continues in the spinal cord

continuation of 4th ventricle

is the red nucleus present at the level of the superior colliculus? inferior colliculus?

yes, no

4 structures in the midline that begin with “M”

motor pathway (corticospinal tract)

medial lemniscus (discriminative touch)

medial longitudinal fasciculus (occular reflexes)

motor nucleus and nerves

4 structures in the side that begin with “S”

spinocerebellar pathway (unconscious proprioceptive info)

spinothalamic pathway (pain/temperature)

sensory nucleus of CN V

sympathetic pathway

4 cranial nerves in each group

4 above the pons: 2 in cerebrum (I, II) and 2 in midbrain (III, IV)

4 in the pons: V, VI, VII, VIII

4 in the medulla: IX, X, XI, XII

what tract is a motor pathway from M1 to the opposite side of the body?

corticospinal tract

what tract carries pain and temperature information from other side of body to S1?

spinothalamic tract via anterolateral system

what tract contains vibration and proprioception from other side of body to S1?

dorsal column - medial lemniscus tract