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103 Cards in this Set
- Front
- Back
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First we look at the midbrain and it's general areas
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Start!
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What can you see in the front of the midbrain?
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The crus cerebri as longitudinal fibers going to the frontal lobe. In between these, there is the interpeduncular fossa.
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What can you see in the back of the midbrain?
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4 swellings called the superior and inferior colliculi
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What are the boundaries of each cerebral peduncle?
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Each peduncle is one half of the midbrain and extends the whole length from front to back
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Draw the side/top view of the midbrain and label peduncle, tectum, tegumentum, base, cerebral aqueduct, and substantia niagra.
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Explain those boundaries.
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Everything in front of SN is the base/crus cerebri
Everything in back of the cerebral aqueduct (which is very posterior in the midbrain) is the tectum. Everything in between is the tegmentum. These are all part of the peduncle. |
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How do ypou remember that the superior colliculi is for eyes and the inferior one is for audio reflexes?
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Your eyes are above your ears.
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What is the result of stimulation to either colliculi?
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movement of the body as a reflex.
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Draw a lateral view of the pathways to and from both the tectum colliculi.
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What just happened?
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You have visual info going to the SC from the eyes and auditory info coming from the pontinemedullary junction to the IC. Then you have motor fibers going from the tectum down the spinal cord to control muscles.
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Now we study the internal structures of the midbrain at the level of the inferior and then superior colliculus.
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Bring it!
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TRANSECTION AT THE LEVEL OF THE INFERIOR COLLICULUS!
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oh yeah!
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Draw and label the two parts of the substantia niagra.
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What just happened? What are the two sections called and why?
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There is the Pars Compacta in the posterior half and Pars Reicularis in the front. The compacta is much more compact with cell bodies than the reticularis which is more like a network.
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What does "pars" mean?
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"part"
so it is part of an anatomical structure |
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Draw a side view of the SN. How long does it span longitudinally? What connections does it have to the cerebrum?
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What just happened?
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SN spans the whole height of the midbrain and connects anterosuperiorly to the caudate putamen/striatum.
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What is the pathway between the caudate putamen and the substantia niagra called? What NT's does it release?
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niagro-striatal dopaminergenic pathway which releases dopamine
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What disease happens when you damage the substantia niagra or the striate pathway?
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parkinson's
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How do you remember the neurotransmitter involved in parkinson's and the symptom?
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Remember the move "Awakenings" where they gave locked in people L-DOPA to make more dopamine and they could move again.
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What is wrong with people with parkinson's? (4 Symptoms)
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1. Hypokinesia
2. Rigidity 3. Loss of postural reflexes 4. Tremors |
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Explain hypokinesia and a way to remember it with Parkinson's.
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They have difficulty initiating movement, which is shown when they start slowing down a lot.
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How may hypokinesia manifest in the face?
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They have difficulty making facial expressions because they are so quickly needed. It looks like they are wearing a mask.
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When have I experienced hypokinesia in the past?
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When I get sleep paralysis and can't move my body.
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Explain rigidity and a way to remember it with Parkinson's.
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In the movie Awakenings, they are all in a catatonic and rigid state.
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Explain loss of postural reflexes and a way to remember it with Parkinson's.
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In Parkinson's if you push them over, they will fall down easily unlike normal people which naturally resist.
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Explain tremors and a way to remember it with Parkinson's.
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In the movie, Lennard's first signs that the L-DOPA is no longer working is that he starts getting facial ticks.
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What are the two mechanisms that can cause Parkinson's?
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Either the pathway is damaged or there is some sort of anti dopaminergic agent in the system.
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What kinds of fibers are associated with the base, tectum, and tegumentum of the midbrain generally? How is this similar to the pons?
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Base- downgoing fibers
Tectum- fibers for hearing and vision Tegumentum- local connections and upgoing sensory fibers. Base and tegumentum are same as in pons (makes sense) |
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NOW WE TALK ABOUT THE BASE OF THE MIDBRAIN
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CRUSCEREBRI TIME!
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What types of fibers pass through the crus cerebri. Name the three examples.
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Descending motor fibers
1. Corticospinal 2. Corticonuclear 3. Corticopontine |
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Draw a side view of all these motor fibers going through the crus cerebri and their origin and termination. Label it.
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What just happened?
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Corticopontine fibers originate all over the cortex and terminate at pontine nuclei
Corticospinal and corticonuclear fibers originate from the motor cortex and terminate on the spinal cord and pons/medulla respectively. |
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Which nuclei do the corticonuclear fibers control?
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nuclei of CN 7, 9, and 12
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Draw the location of the motor fibers in the cross section of the crus cerebri and label them.
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What just happened?
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The corticospinal fibers occupy the interior 3/5th of each peduncle.
The corticopontine fibers fill in the exterior 1/5th of both sides of each peduncle. The corticonuclear fibers are interspersed with the corticopontine in the medial parts of both peduncles. |
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NOW WE TALK ABOUT THE TECTAL PORTION OF THE CROSS SECTION OF THE INFERIOR MIDBRAIN.
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sO MANY PARTS!
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Draw a picture of the cross section of the tectum at the inferior midbrain. (There are three fibers here)
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Explain what just happened. What are the three fibers and what do they do?
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Auditory info comes from the lateral leminiscus inferiorly and connects to the inferior colliculi. This is then transmitted upwards by the brachium (arm) of the inferior colliculi. The two colliculi are joined by the commissure of the inferior coliculus.
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If one colliculus is damaged, where would we lose hearing to?
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Trcik questions! We would reatin hearing because some of the fibers in the trapezoid body cross and some don't so each colliculus gets info from both ears.
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Why is the commisure of the inferior colliculus called what it is? What does it do?
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It spans left and right and is a tract so it is the definition of a commisure. It helps the two colliculi to communicate with one another.
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Where do the brachium fibers go after the inferior colliculi?
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The medial genticulate body of the thalamus
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Can you draw and label the genticulate bodies of the thalamus?
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Explain what just happened.
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They are little tumors on the side of the lateral part of the thalamus. medial is more slightly medial and lateral is more lateral.
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NOW WE TALK ABOUT THE TEGUMENTUM
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WHEEE
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What level is the red nucleus located at?
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the upper part of the midbrain at the more anterior part of the tegumentum
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What pathway goes from the cerebellum to the red nucleus?
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The denticulate rubro thalamic pathway
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Draw a front and side view of the denticulate rubro thalamic pathway.
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Explain what just happened. Where are the fibers coming from and where do they cross.
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Fibers coming from a large nucleus in the cerebellum called the denticulate nucleus go up to the red nuclei, but cross in the lower midbrain. They then ascend to the thalamus.
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Show the cross section of the lower midbrain with the crossing of the denticulate-rubro pathway and all the leminisci in there as well.
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Explain what just happened.
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The crossing of the denticulate-rubro pathway is just dorsal to where the SN makes a corner in the middle. The leminisci are just lateral to it with the lateral leminiscus ending at the inferior collicuus.
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Which leminiscus will you see in the upper midbrain?
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the medial and spinal leminiscus.
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Draw in the nucleus and pathway of CN 4 in the cross section. What is unite about the path of CN 4? (2 things)
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1. it exits out the back
2. It crosses before it exits |
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What just happened?
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the nuclei are tightly on either side of the cerebral aqueduct. they decussate posteriorly and exit out between the two inferior colliculi to go out and to the front of the midbrain.
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What does CN 4 innervate? (specify the side)
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the contralateral superior oblique
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Draw in the medial longitudinal fibers.
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Explain what just happened and why this makes sense fros transitioning from the pons.
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The paired fibers are right in front of the cerebral aqueduct between the CN 4 nuclei.
It was in the back between the genu of the 7th CN in the lower pons and followed the ventricles up. |
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What cranial nuclei does the medial longitudinal fibers serve? Why?
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All the eye ones: 3, 4, and 6
and the vestibular nuclei because based on your sense of where our head is, you coordinate your eye movement |
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So what can deduce about the location of the medial longitudinal fibers from this one fact?
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It will always be between these cranial nuclei so it will be medial. Also these are mainly motor nuclei so they will be in the medial and dorsal part of the tegumentum.
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Draw the extra nuclei in periaqueductal grey matter in the cross section of the lower pons.
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List the nuclei in the periaqueductal grey matter that were just drawn
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1. Mesencephalus part of trigeminal nucleus
2. Locus Coeruleus 3. Nucleus raphe 4. Central tegumental nuclei |
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Draw a frontal picture of where the fibers from nucleus raphe and the dorsal tegumental pathway go.
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Explain what just happened?
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These two nuclei send pathways down to the spinal cord dorsal horns ipsilaterally to secrere morphine-like substances to modulate pain.
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What substances do the nucleus raphe and the dorsal tegumental pathways release respectively?
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nucleus raphe- serotonin
dorsal tegumental- enkephalins |
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What part of the pain system are these nuclei intervening at?
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At the level of pain entry into the spinal cord to inhibit PAIN TRANSMISSION
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What is the nucleus in the midbrain that is involved in eating behavior?
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The interpeduncular nucleus named for it's location.
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Draw in the interpeduncular nuclei and it's superior connection in the midbrain cross section.
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What does the the habencular-interpeduncular pathway regulate?
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eating behavior
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Draw in a lateral view of the habencular-interpeduncular pathway.
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Explain what just happened.
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Hypothalamus sends fiber to hbencular nucleus posterior to the thalamus, which sends fibers via the retroflux fasiculus to the interpeduncular nucleus in the anterior and inferior part of the midbrain.
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Is the reticular formation present in the midbrain? Where?
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Yes, it is present all the way up to the thalamus and is interspersed in the middle of the tegumentum.
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Now we talk about the central tegumental pathway!
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my favorite subject....
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What kind of tract is the central tegmental pathway?
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A roasted tract.
ROST |
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What is the mnemonic for ROST for the central tegmental pathway?
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Reticular formation
Olivary nucleus S Thalamus |
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That was really far from a perfect mnmonic. What are the 3 tracts involved in the central tegmental pathway?
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1. rubro-olivary
2. reticulothalamic (intralaminary nuclei of thalamus) 3. taste fibers from NTS to the VPM thalamus |
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Draw where the central tegmental pathway is on the cross section.
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Explain how you can deduce this?
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Since it carrles fibers for the reticular formation, it must be behind it. Also, since it carries the fibers for taste, it must be right above the NTS area.
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NOW WE TALK ABOUT THE SUPERIOR PART OF THE MIDBRAIN!
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OK!
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What is the main difference in the cross section of the superior midbrain?
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the crossing of the denticulate rubro pathway has fulminated into the red nuclei.
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What are the main functions of the red nucleus?
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1. to help coordinate flexion movements (sit on a rubber mat)
2. help with wrist movement to help with things like writing. |
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Draw a front view of all the connections of the red nucleus. (3)
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Describe what just happened.
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1. Contralateral connections with cerebellum
2. Contralateral connections with motor cortex and then fibers to modulate flexion LMN's 3. Ipsilateral connection with olives. |
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What two nuclei are present in the superior midbrain? (2)
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The nuclei of CN 3 and the Edinger Westphal nucleus.
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What type of autonomic system is the Edinger Westphal nuclei? How do you know?
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Since it is cranial, it must be parasympathetic
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Draw how these two nuclei are arranged and how they exit the midbrain.
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Explain what just happened? How do you know their placement?
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CN 3 nuclei are right above CN 4 because they are the same type. The parasympathetic nuclei are just lateral to them because that's where autonomic nuclei are. They merge early on to make CN 3 which passes through the red nucleus and SN to exit out of the interpeduncular fossa.
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What muscles do CN 3 control?
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All the extraoccular muscles except the ones controlled by CN 6 and CN 4 (superior oblique and lateral rectus)
AND the muscles that raise the eyebrows |
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What does the Edinger Westphal fibers control?
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Intraoccular muscles like the ciliary muscles and the ones that control pupil constriction.
Ciliaris and sphincter pupilae |
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Draw out how CN 3 and the Edinger Westphal connect to the eye.
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What just happened?
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CN 3 goes straight to it's targest whereas Edinger Westphal has to go to a cilliary gang;ion first.
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So what nerve is firing when your pupils constrict from a strong light or from an object moving closer?
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This is all the work of the edinger westphal!
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What kind of signals go to the superior colliculi from occipital vs frontal eye field.
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occipital- tracking eye field
frontal eye field- searching movements |
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If you are searching for your wife and then see a beautiful girl and start staring at her walk by, which cortical areas are active at each time?
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frontal eye field and then occipital
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How do you remember that frontal eye field is searching?
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this is the push buttons of the eyes and makes you look left and right, which is what you do when you search. When you are tracking, your head moves.
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What nuclei help with the light reflexes? Where are they?
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the pretectal nuclei in front of the superior colliculi
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Show a picture of the location and connections of the pretectal nuclei
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What are the connections that the pretectal nuclei have?
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Connections with one another and with the edinger westphal nuclei
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What is the connection between the two pretectal nuclei called?
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posterior commissure.
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So what are all the commissures we have in the midbrain?
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commisure of superior colliculi
commisure of inferior colliculi commisure of pretectal colliculi aka posterior commissure |
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What are all the fibers coming out of the colliculi called? How do you remember this?
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inferior or superior brachium because they stop at the thalamus before going to the cortex which looks like this part is an upper arm and the thalamus is the elbow.
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Which part of the thalamus does each brachium go to?
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They go to the weird outgrowths
inferior to medial genticulate body (MGB) superior to lateral genticulate body (LGB) |
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What does the posterior commissure of the pretectal nuclei allow us to coordinate?
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bilateral stimulation of EWN to constrict bot pupils if one has a flashlight on it.
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Is the edinger westphal nucleus part of CN 3?
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Yes, according to first aid
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