BMB 1 - Brainstem Nuclei & Tracts Flashcards
Identify the three major portions of the brainstem in this image.
What are the three longitudinal portions of the brainstem?
Basis (basement - dark gray)
Tegmentum (floor - light gray)
Tectum (roof - labeled)
Which longitudinal tract of the brainstem contains tracts from the cortex (especially the corticospinal)?
The basis (basement - dark gray)
The tegmentum of the brainstem (the light gray) contains which cranial nerve nuclei?
III - XII
(all but I and II)
What structures are associated with the tectum?
Midbrain integrative structures - e.g. center for vision (superior colliculus) or hearing (inferior colliculus)
Identify the cranial nerves which emerge from the midbrain.
CN III and IV
Identify the cranial nerves which emerge from the pons.
V, VI, VII, VIII
Identify the cranial nerves which emerge from the medulla.
IX, X, XI, and XII
Which cranial nerves exit ventrally?
Which cranial nerves exit dorsally?
All but IV;
IV only
Where does the trochlear nerve exit the midbrain?
Dorsally; inferior to the inferior colliculus
Where does the trigeminal nerve exit the brainstem?
Near the middle cerebellar peduncle
Where does the abducens nerve exit the brainstem?
Medially; along the pontomedullary junction
Where does the facial nerve exit the brainstem?
Along the pontocerebellar junction;
lateral to CN VI
Where does the vestibulocochlear nerve exit the brainstem?
Along the pontocerebellar junction;
lateral to CN VII
Where does the glossopharyngeal nerve exit the brainstem?
The groove dorsal to the olive in the postolivary sulcus
Where does the vagus nerve exit the brainstem?
The groove dorsal to the olive in the postolivary sulcus
Where does the accessory nerve exit the brainstem?
It does not;
it exits the cervical spinal cord (not technically a cranial nerve)
Where does the hypoglossal nerve exit the brainstem?
Between the pyramid and the olive (in the pre-olivary sulcus)
In what structures do the dorsal columns end?
The gracile and cuneate tubercles
Of the cerebellar peduncles, which provide the major input to the cerebellum?
The middle cerebellum peduncles
Of the cerebellar peduncles, which provide the major output from the cerebellum?
The superior and inferior cerebellar peduncles
From caudal to rostral, what are the four main parts of the internal organization of the brainstem?
Closed medulla >
Open medulla >
Pons >
Midbrain
Of the four main parts of the internal organization of the brainstem (closed medulla, open medulla, pons, midbrain), in which do the fasciculus cuneatus and fasciculus gracilis terminate?
The closed medulla
This is a cross-section of what portion of the brainstem?
The closed medulla
(the otter)
This is a cross-section of what portion of the brainstem?
The open medulla
(the bulldog)
This is a cross-section of what portion of the brainstem?
The pons
(Snidely Whiplash)
This is a cross-section of what portion of the brainstem?
Midbrain
(the stingray)
What are the shape mnemonics for the four main parts of the internal brainstem organization as seen in cross-section?
Midbrain
Pons
Open medulla
Closed medulla
Stingray
Snidely Whiplash
Bulldog
Otter
In which of the four main parts of the internal brainstem organization does most sensory decussation occur (via the medial lemniscus pathway)?
Midbrain
Pons
Open medulla
Closed medulla
The closed medulla
Where are the nuclei gracilis and cuneatus in the brainstem?
The closed medulla
In which of the four main parts of the internal brainstem organization are the second-order sensory neuron cell bodies?
Midbrain
Pons
Open medulla
Closed medulla
The closed medulla
(the nucleus cuneatus and gracilis)
In which of the four main parts of the internal brainstem organization are the hypoglossal nuclei?
Midbrain
Pons
Open medulla
Closed medulla
The open medulla
In which of the four main parts of the internal brainstem organization is the inferior cerebellar peduncle?
Midbrain
Pons
Open medulla
Closed medulla
The open medulla
In which of the four main parts of the internal brainstem organization are the olives?
Midbrain
Pons
Open medulla
Closed medulla
The open medulla
The brainstem olive is connected to the cerebellum and helps facilitate _____________ movement.
The brainstem olive is connected to the cerebellum and helps facilitate pre-programmed movement.
In a cross-section of the pons (which looks like Snidely Whiplash), which part of the cross-section looks like a mustache way at the bottom of the section?
The ponto-cerebellar fibers
The substantia nigra and superior colliculi are both found in what section of the brain?
The midbrain
In cross-section of the midbrain (which looks like a stingray), describe where the superior colliculi and substantia nigra are.
Where (specifically) in the brain is the reticular formation found?
The tegmentum in all levels of the brainstem
The _______ (rostral/caudal) portion of the reticular formation maintains an alert, conscious state in the forebrain.
The rostral portion of the reticular formation maintains an alert, conscious state in the forebrain.
The _______ (rostral/caudal) portion of the reticular formation connects to cranial nerve and spinal nuclei and controls various motor, reflex, and autonomic functions.
The caudal portion of the reticular formation connects to cranial nerve and spinal nuclei and controls various motor, reflex, and autonomic functions.
The reticulospinal tract aids in maintaining tone and balance and is a projection from what tegmental structure?
The caudal reticular formation
A patient suffers a stroke leading to ischemia of their reticular formation.
What two major effects do you expect in particular?
- Loss of consciousness
- Impaired breathing
Name the respective nuclei in the reticular formation that secrete each of the following:
Serotonin
Acetylcholine
Norepinephrine
Dopamine
Raphe magnus
Pedunculopontine
Locus ceruleus
Ventral tegmental area
The pyramidal tracts in the brainstem are mainly involved in transmitting signals involved in what?
Motor control
(corticospinal and cerebellar functions)
What is the purpose of the long tracts of the brainstem?
To connect the higher order cerebral structures to the spinal cord
What are the three long tracts of the brainstem?
- The corticospinal
- The somatosensory (spinothalamic + medial lemniscus)
- The trigeminal system (chief sensory + trigeminothalamic)
Describe how the corticospinal tracts travel through the brainstem.
(The majority of decussation occurring towards the caudal portion)
Where do 90% of corticospinal fibers decussate (i.e. where does pyramidal decussation occur)?
The lower medulla
The corticospinal fibers come from Brodmann area 4, travel through the ___________ of the midbrain, travel through the _____ pontis of the pons, and decussate at the lower medulla.
The corticospinal fibers come from Brodmann area 4, travel through the cerebral peduncle of the midbrain, travel through the basis pontis of the pons, and decussate at the lower medulla (to then become the _lateral_ corticospinal tract in the spinal cord).
True/False.
The corticospinal tract travels mainly through the tegmentum of the brainstem (light gray).
False.
The corticospinal tract travels mainly through the ventral (basis) of the brainstem (dark gray area in previous image).
What is the significance of the corticospinal tract mainly being in the basis (anterior portion) of the brainstem?
It is far from the vertebral and basilar arteries
(and thus extra susceptible to ischemic damage)
The corticospinal tract is responsible for voluntary motor control and travels ipsilaterally through the brainstem, through the _______ _______ in the midbrain, the _______ _______ in the pons, and the _______ in the medulla.
The corticospinal tract is responsible for voluntary motor control and travels ipsilaterally through the brainstem, through the cerebral peduncle in the midbrain, the basal pons in the pons, and the pyramids in the medulla.
Neurons of the lateral corticospinal tract synapse in the _______ _______ of the spinal tract.
Neurons of the lateral corticospinal tract synapse in the anterior horn of the spinal tract.
The neurons that synapse directly on skeletal muscle and cause voluntary muscle contraction are ____ motor neurons.
The neurons that synapse directly on skeletal muscle and cause voluntary muscle contraction are α motor neurons.
Why does brainstem ischemia often cause issues with voluntary motor control?
The blood supply is in the tegmentum (dorsal), and the corticospinal tract is in the basement (ventral)
Damage to the corticospinal tract in the brainstem is most likely to lead to what motor S/Sy?
Upper motor neuron signs
- Babinski sign
- Spastic paralysis
- Contralateral hemiparesis
Name the three S/Sy of upper motor neuron lesions.
- Babinski sign
- Spastic paralysis
- Contralateral hemiparesis
Describe where in the cross-sections of the brainstem you would find the corticospinal tract.
Note: this includes the midbrain, pons, pontomedullary junction, open medulla, and closed medulla.
Which are the two brainstem tracts that make up the somatosensory tract?
The spinothalamic and medial lemniscus
The dorsal column first-order neurons synapse with second-order neurons in which nuclei?
And where do these second-order neurons synapse with third-order neurons?
The medulla nucleus gracilis and cunateus;
the thalamic VPL
Second-order neurons in both the spinothalamic and medial lemniscus tracts synapse on third-order neurons in what nucleus?
The ventral posterolateral nucleus
(the thalamic VPL)
How can one check the integrity of the dorsal column - medial lemniscus system?
The Romberg test
True/False.
The nucleus gracilis and nucleus cunateus are located in the pons.
False.
The nucleus gracilis and nucleus cunateus are located in the medulla.
True/False.
The ventral posteromedial and ventral posterolateral nuclei are located in the pons.
False.
The ventral posteromedial and ventral posterolateral nuclei are located in the thalamus.
In the pons and midbrain, secondary neurons of the medial lemniscus are _______ (medial/lateral/ventral/dorsal) to secondary neurons of the anterolateral system (spinothalamic tract).
In the pons and midbrain, secondary neurons of the medial lemniscus are medial to secondary neurons of the anterolateral system (spinothalamic tract).
What sensory information is carried by the dorsal columns - medial lemniscus pathway?
- Discriminatory touch
- Conscious proprioception
- Vibration
What sensory information is carried by the spinothalamic pathway?
- Pain
- Itch and tickle
- Crude touch
(strong stimulus needed)
Where do first-order neurons of the spinothalamic tract decussate and synapse?
Where do second-order neurons of the spinothalamic tract synapse?
The nucleus proprius; the anterior white commissure;
the thalamic ventral posterolateral nucleus
Describe the pathways of the medial lemniscus and spinothalamic tracts through the brainstem.
Describe the locations of the medial lemniscus and spinothalamic tracts on cross-section of the closed medulla.
Describe the post-decussation pathway of the medial lemniscus as seen on cross-section of the open medulla, pons, midbrain, and inferior colliculus.
Describe the locations of the medial lemniscus and spinothalamic tracts on cross-section of the open medulla, pons, and midbrain.
The brainstem trigeminal system consists of two tracts: the _____________, which carries discriminatory sensation from the face, and the _____________, which carries pain and temperature sensation from the face.
The brainstem trigeminal system consists of two tracts: the chief sensory, which carries discriminatory sensation from the face, and the trigeminothalamic, which carries pain and temperature sensation from the face.
The chief sensory tract (CN V) synapses in the ___________ nucleus, and the trigeminothalamic tract (CN V) synapses in the ___________ nucleus.
The chief sensory tract (CN V) synapses in the chief sensory nucleus, and the trigeminothalamic tract (CN V) synapses in the spinal tract of V nucleus.
Which thalamic nucleus carries sensory information from the body?
Which thalamic nucleus carries sensory information from the face?
The ventral posterolateral nucleus;
the ventral posteromedial nucleus
True/False.
The chief sensory tract (CN V) synapses in the chief sensory nucleus, decussates, synapses in the ventral posterolateral nucleus of the thalamus, and then continues to the cortex.
True.
True/False.
The trigeminothalamic tract (CN V) synapses in the chief sensory nucleus, synapses in the ventral posterolateral nucleus of the pons, decussates, and then continues to the cortex.
True/False.
The trigeminothalamic tract (CN V) synapses in the spinal nucleus of V, decussates, synapses in the ventral posteromedial nucleus of the thalamus, and then continues to the cortex.
The chief sensory tract (CN V) carries what type of information from the face?
The trigeminothalamic (CN V) carries what type of information from the face?
Discriminatory sensation;
pain and temperature
Describe the location of the spinal nucleus of V in the closed medulla in relation to the medial lemniscus pathways.
Describe the locations of the spinal tract of V in the open medulla, pons, pontomedullary junction, and midbrain.
Which tracts intrinsic to the brainstem are found in the superior colliculus?
Tectospinal and spinotectal tracts
What is the function of the superior colliculus?
To mediate reflex turning of head and neck in response to visual stimuli
Identify the portions of the midbrain indicated by arrows.
What is the function of the inferior colliculus?
To receive auditory information from the lateral lemniscus and relays to thalamus
What is the function of the periaquaductal grey matter?
To modulate pain signals to the spinal cord substantia gelatinosa
Which two large structures receive output from cerebellum and sends fibers back to the cerebellum?
What tract projects from these structures to the anterior horn of the spinal cord in order to control contralateral distal musculature?
The red nuclei;
the rubrospinal tracts
Where is the substantia nigra located?
What two tracts project from the substantia nigra?
The ventral tegmentum of the midbrain;
nigrostriatal and striatonigral tracts
If you can see the superior colliculus on a cross-section of the midbrain, will the red nuclei be visible?
If you can see the inferior colliculus on a cross-section of the midbrain, will the red nuclei be visible?
Yes;
no
Where do nerve fibers to and from the cerebellum (an ipsilateral system) decussate before reaching the cortex (a contralateral system)?
The pontocerebellar fibers (entering the cerebellum at the middle cerebrellar peduncle);
the superior cerebellar penducle (exiting the cerebellum)
Name two structures found within the basis pontis.
The superior olivary nucleus and lateral lemniscus
The middle cerebellar peduncle is found in what portion of the brainstem?
The inferior cerebellar peduncle is found in what portion of the brainstem?
The pons;
the open medulla
The ________ cerebellar peduncle is responsible for unconscious proprioception, coordination, and balance. Damage to this structure is often due to stroke of vertebral artery or PICA and results in swaying or staggering to the _____lateral side.
The inferior cerebellar peduncle is responsible for unconscious proprioception, coordination, and balance. Damage to this structure is often due to stroke of vertebral artery or PICA and results in swaying or staggering to the ipsilateral side.
Name the portions of the reticular system responsible for each of the following:
(1) Reward, arousal, consciousness, and sleep
(2) Breathing
(3) Balance, posture, axial control
(3) Cardiac function
(1) Ascending reticular activation system
(2) Respiratory centers
(3) Reticulospinal pathway
(4) Cardiac control center
True/False.
Damage to the hypothalamospinal tracts (e.g. in the reticular system) can lead to Horner’s syndrome.
True.
