CNS Unit 10 Eye movements and Brainstem pt. 3 Flashcards
What muscles does the Oculomotor Nerve Innervate?
CN 3
- Levator Palpebae
- Superior Rectus
- Inferior Rectus
- Middle Rectus
- Inferior Oblique
The oculomotor nerve has a parasympathetic function. What is the name of the Accessory Parasympathetic Nucleus?
What is this for?
Edinger-Westphal Nucleus
This is for Pupil Constriction
What is the difference between Direct Response and Consensual (Indirect) Response in terms of pupil constriction?
If light is shined on the Right eye and the Right eye constricts, this is called Direct Response. On the opposite eye its called the Consensual (Indirect) Response.
What is the Accommodation-Convergence Reflex in the eye?
This is when there is a change in shape of the lens and constriction of pupil, while the eyes move in to focus on the near object
Example: Holding a pen in front of your face and looking at the wall then switching to looking at the pen.
What would happen if CN 3 were damaged?
- The eye would deviate laterally
- The pt would have Diplopia (Blurred Vision)
- The pt would have Ptosis (Drooping eyelid)
- The pupil will not constrict (But this wont affect the contralateral side)
Both the Pupilary and Accommodation-convervence reflex will be affected on the ipsilateral side
What is the function of the Trochlear Nerve?
CN 4
Motor to Superior Oblique
Where is the nucleus for the Trochlear Nerve found?
Found in the Periaqueductal Gray at the level of Inferior Colliculus
How does the Trochlear Nerve leave to get to the Superior Oblique muscle?
Leaves posterior and wraps around to the ventral side of cerebral peduncle into cavernous sinus area then into Superior Orbital Fissue then to the Superior Oblique muscle
What would happen if the Trochlear Nerve were damaged?
- There would be difficulty moving the eye down and laterally
- There may be a vertical/medial strabisums or vertical diplopia
What is the Function of the Abducens Nerve?
CN 6
Motor to Lateral Rectus
Where is the nucleus for Abducens Nerve found?
The nuclei is found in the pons below the floor of the 4th ventricle near the Facial Colliculus
How does the Abducens exit to get to the Lateral Rectus?
Exits at Pontomedullary Junction and travels through cavernous sinus area and then through the Superior Orbital Fissue to the Lateral Rectus
What would happen if the Abducens Nerve were to be damaged?
- There would be difficulty turning the eye outward (laterally)
- Leads to medial strabismus or diplopia
What test is very good at testing the different CN of they eye along with the muscles?
The “H” Test
When the Eye is Abducted, what does the Superior Rectus act as?
The Superior Rectus acts as a Pure Elevator when the eye is abducted
When the eye is Abducted, what does the Inferior Rectus act as?
The Inferior Rectus acts as a Pure Depressor when the eye is abducted
When the eye is Adducted, what does the Superior Oblique act as?
The Superior Oblique acts as a Pure Depressor when the eye is adducted
When the eye is Adducted, what does the Inferior Oblique act as?
The Inferior Oblique acts as a Pure Elevator when the eye is adducted
What are the Main Components of the Brainstem?
- Cranial Nerves
- Long Tracts (Motor and Sensory Pathways)
- Reticular Formation (The core of the brainstem)
- Cerebellum
On the Ventral side, what CN is associated with the Midbrain?
Oculomotor Nerve
On the Dorsal side, what CN is associated with the Midbrain?
Trochlear Nerve
What are the 3 main areas of the Midbrain?
Tectum, Tegmentum, and Basis
- The Tectum is the “roof”, its a cut of either the superior or inferior colliculi
- The Tegmentum makes the bulk of the midbrain, here you find the red nucleus
- The Basis is the most ventral portion, this is where we have a large collectionof fibers for the corticobulbar and corticospinal tracts
(Corticobulbar pathways carrying info from the cortex to brainstem;
Corticospinal is info carried from cortex to spinal cord-motor info)
What are the Myelin-Stained sections of the Midbrain at the level of the Superior Colliculi?
- Edinger-Westphal Nucleus (CN 3)
- Oculomotor Nucleus
- Mesencephalic Trigeminal Nucleus (CN 5)
- Red Nucleus
What are the Myelin-Stained sections of the Midbrain at the level of the Inferior Colliculi?
- Trochlear Nucleus
- Fascicles of Trochlear nerve
- Superior Cerebellar Peduncle and Decussation
In the Midbrain what is the function of th Periaqueductal Gray?
Pain Modulation
Associated with the Spinothalamic Tract
On the Ventral side, what CN is associated with the Pons?
- Trigeminal (V)
- Abducens (VI)
- Facial (VII)
- Vestibulocochlear (VIII)
On the Dorsal side, what structures are associated with the Pons?
- Facial Colliculus
- Cerebellar Peduncles: Superior, Middle, Inferior
- Fourth Ventrical
On the Ventral side, what CN is associated with the Medulla?
- Glossopharyngeal
- Vagus
- Spinal Accessory
- Hypoglossal
What are the Myelin-Stained sections of the Open Medulla?
- Inferior Olvary Nucleus: Dorsal Accessory, Principal, Medial Accessory
- Vestibular Nuclei
- Solitary Nucleus (CN VII, IX, X)
- Dorsal Motor Nucleus of Vagus (CN X)
- Hypoglossal Nucleus ( CN XII)
- Spinal Trigeminal Nucleus (CN V, VII, IX, X)
- Nucleus Ambiguus (CN IX, X, XI)
What are the Myelin-Stained sections of the Closed Medulla?
- Cuneate Nucleus
- Gracile Nucleus
- Medial Lemniscus and Sensory Decussation
What is the Function of the Rostral Reticular Formation?
This merges with the subglobttic region and lateral Hypothalamus
- This communicates with the subthalamic area
- This deals with alertness and states of consciousness as well as Arousal
What is the Function of the Caudal Reticular Formation?
This merges with the spinal cord
- This works with the Cranial Nerve nulei and spinal cord, to carry out reflexes, motor and autonomic functions
What are the cortical areas that are associated with the Rostral Reticular Formation?
- Medial/Lateral Parietal Association Cortex: This deals with communication of the rostral portion of arousal circuits, these arousal ciruits also reside in the upper brainstem and diencephalon
What are the Levels of Consciousness?
The 3 A’s
- Alertness: Brainstem and arousal circuits
- Attention: Additional processing in frontoparietal association cortex
- Awareness: Subjective and personal experience
Subcotical Arousal Systems
What do the Upper Brainstem Neurons release? Where do they project?
The typically release the neurotransmitter Norepinephrine, Serotonin, and Dopamine
- They project to cortical and subcortical forebrain
“How the system wakes up”
Subcortical Arousal Systems
What do the Upper Brainstem Neurons and Pontomesencephalic Reticular Formation Neurons Release? Where do they project?
Release Acetylcholine and Glutamate
- They project to the thalamus, hypothalamus and basal forebrain
Subcortical Arousal Systems
What do the Posterior Hypothalamic Neurons release? Where do they project?
Release Histamine and Orexin
- They project to cortical and subcortical targets
Subcortical Arousal Systems
What do the Basal Forebrain Neurons release? Where do they project?
Typically release Acetylcholine
- It projects to the cerebral cortex
Subcortical Arousal Systems
What do the Neurons in the Rostral Thalamic Intralaminar Nuclei and Medial Thalamic Nuclei release? Where do they project?
Release Glutamate
- Projects to the Cerebral cortex
How may a patient present if they have damage in the Upper Brainstem Ponsomesencephalic reticular formation?
The patient may be in a coma
What are the Major Inputs to the Pontomesencephalic Reticular Formation?
- Thalamic reticular nucleus
- Limbic and Cingulate Cortex (Deals a lot with emotion)
- Frontoparietal Association Cortex
- Sensory inputs coming from peripherary
Where are the locations of cell bodies of Norepinephrine?
Pons: Locus ceruleus and lateral tegmental area
What is the Main Target for Norepinepherine?
The Entire CNS
What is the Function of Norepinephrine?
Alertness, and mood elevation
Important for sleep wake cycle
Where is the location of the cell bodies of Dopanine?
Midbrain: Substantia nigra par compacta and ventral tegmental area
What are the Main targets for Dopamine?
Striatum, Limbic Cortex, Amygdala, Nulceus Accumbens and Prefrontal Cortex
What is the Function of Dopamine?
Movement initiative and working memory
Where is the location of cell bodies of Serotonin?
Midbrain, Pons, and Medulla: Raphe Nuclei
What is the Main Target for Serotonin?
Entire CNS
What is the Function of Serotonin?
Alertness, Mood elevation, breathing control
Where is the location of cell bodies for Acetycholine?
2 areas
- Basal Forebrain: Nucleus Basalis, medial septal nucleus, and nucleus of diagonal band
- Pontomesencephalic Region: Pedunculoponine nucleus and laterodorsal tegmental nucleus
What are the Main Targets for Acetycholine?
Consider that theres 2 locations for this
If in Basal Forebrain: Cerbral Cortex including Hippocampus
If in Pontomesencephalic Region: Thalamus, Cerebellum, Pons, Medulla
What is the Function of Acetycholine?
Alertness and Memory
What are the 5 stages of the Sleep Wake Cycle?
- Stages 1-4: Progressively deeper nonREM (non-rapid eye movement)
-Controlled by sertonergic neurons of the Raphe Nuclei - Stage 5: REM (rapid eye movement)
-Controlled by nonadrenergic neurons in the locus cereleus
-Deep sleep
-Dreaming
-Easy to awaken
-Paradoxial sleep: deeper than stage 4 but also resembles the awake state (muscle tone lower, EEG shows lower-voltage mixture of fast activity)
What is the Function of the Caudal Reticular Formation?
- Motor
- Reflex
- Autonomic Function (Respiration, Circulatory Control)
In the Caudal Reticular Formation, what nucleus controls Respiration and circulatory control?
The Nucleus Soltarius (Cardiorespiratory Nucleus) in the Medulla
Caudal Reticular Formation
What controls Respiratory Rhythm under automatic control?
Medulla Circuits
Caudal Reticular Formation
What controls Respiratory Rhythm under Voluntary control?
The Forebrain
This is when we hold our breath, or change the rhythm of our breathing
What artery supplies the Orange Portion?
PCA
What artery supplies the Dark Purple Portion?
Basilar Artery (Para-median branches)
What artery supplies the Light Purple Portion?
The Basilar Artery (Circumferential Branches, or the Lateral Pontine Arteries)
What artery supplies the Green Portion?
SCA
What artery supplies the Dark Blue Portion?
AICA
What artery supplies the Light Blue Portion?
PICA
What atery supplies the Pink Portion?
Vertebral Artery (Lateral Branches)
What artery supplies the Red Portion?
Vertebral Artery (Paramedian Branches) and Anterior Spinal Artery
