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124 Cards in this Set
- Front
- Back
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How did scientists discover what part of the brain does what?
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1.Electrically stimulating different cortical areas
2. Studying deficits in people with brain lesions |
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Where is the primary motor cortex located?
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precentral gyrus
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Show the precentral gyrus
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What are the three horizontal gyri in front?
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Superior, Middle, and Inferior Frontal Gyrus
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Show the 3 frontal gyri. (yellow)
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What are the three separate areas in the cortex that control motor function?
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1. Primary motor cortex
2. Premotor area 3. Supplementary motor area |
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Can you show what they look like in the brain?
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How do you remember that the premotor cortex is the one that is anterior and the supplemental motor cortex is superior and medial?
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Pre seems to mean anterior in the brain so premotor will go in front.
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What do the pre and supplemental motor cortexes do?
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They are involved in programming movements before they are sent to the primary cortex to be executed.
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How are the pre and supplemental cortexes different in function?
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premotor- advanced for limbs and talking
supplementary motor- primitive movement like the trunk and hip |
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What does this mean to trying to actively resist an urge?
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Your brain is already halfway down the road of giving in.
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What kind of sensory input do you need before executing a planned conscious motor action?
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You need proprioception information about where your body is so that you know where your starting point is.
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What else do you need to have before executing an action?
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An idea of what you would like to achieve, which can come from many different places in the brain.
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Are you only moving the muscles that you plan to move?
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No, on their way down, motor neurons send off collateral branches to adjust postural muscles to hold the rest of your body stable. This is unconscious.
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So does this mean that there is one or multiple motor tracts going down?
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Multiple. One straight from consciousness (cortical) and others that are subcortical.
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What kinds of decision making takes place in the primary motor cortex?
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This area houses the final motor neurons that are just told what to do by the pre and supplemental motor cortexes.
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What happens when you stimulate one area of the primary motor cortex?
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you get one meaningless movement like a knee jerk
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What happens when you stimulate one area of the pre or supplemental motor cortex?
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You get a meaningful program of actions like a word.
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Imagine the area that allows you to execute a constellation of actions to speak. What is it called?
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What muscles do you need in order to speak?
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Larynx, tounge, facial muscles
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So what types of neurons are on the primary motor cortex next to Broca's area?
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Those very motor neurons!
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Mnemonic to differentiate Broca's and Wernicke's areas?
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Tom Broca is a reporter who really likes to talk!
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What do pt's experience when they have damage to Broca's area?
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They know what they want to say (planning is intact), but they can't say it (programming portion is missing)
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What area is above Broca's area on the premotor cortex?
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the frontal eye field
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What does the frontal eye do?
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It is the push button for the eyes and will cause eyes to shift to the contralateral side.
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Show the frontal eye field.
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How are the frontal eye fields operating normally?
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Both sides are equally active.
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What is you have a lesion on the right frontal eye field?
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Your eyes will look to the left.
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What happens to activity of neurons when they are irritated?
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They will become over active.
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What happens in the short and long term when you have a tumor in the right frontal eye field? Why?
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Short term- look to left because tumor substances are iriitating the neurons
Long term- look to right side because tumor has destroyed it |
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Mnemonic for what irritation vs destruction does to your eye position.
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If someone is irritating you, you look away. But if they start to destroy your stuff, you have to look towards.
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What is right above the frontal eye field? Mnemonic?
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The area controlling neck movement because this usually accompanies eye movement.
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What is above the area the neck control area?
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The area for controlling fine hand movement.
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Premotor cortex controls movement contralaterally. How does the supplemental motor cortex control movement?
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bilaterally!
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Draw the homunculus.
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Why is the homunculus useful for diagnosing?
What do you notice about where the homunculus bends? |
Depending on the dysfunction you have, you can be having damage to that area of the brain.
The homunculus bends at the hips. |
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Where do descending motor fibers come from? (give percentages and layer)
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5th layer of cerebral cortex
primary motor cortex- 30% supplemental and premotor cortexes- 30% Sensory motor cortex- 40% |
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What is special about some of the motor neuron cell bodies? Which area do they come from and what are they called?
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There are large cell bodies found only in the primary motor cortex called cells of Betz.
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How large are cells of Betz? (compare to RBC)
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60 um (about 8x a RBC)
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Are most of the cells in the primary motor cortex cells of Betz?
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No, only some.
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What is special about the axons from cells of Betz?
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they are large and heavily myelinated.
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How much larger are the axons of the cells of Betz?
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4 times larger than others at 16um.
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What is special about the connection the Betz cells have with alpha motor neurons?
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They directly stimulate alpha motor neurons whereas regular ones stimulate an interneuron to do the job.
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Show the comparison of the Betz cell connection.
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What are these interneurons called?
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Internunchal neurons
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How many descending motor neurons are there?
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1 million come down from each cerebral hemisphere.
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How many of each million are coming from the Betz cells?
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30k
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Where do all the descending cortical motor fibers converge on? What is the fanned part called?
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The posterior limb of the internal capsule. The fanned part is also called the corona radiata.
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What is the pathological implication of the convergence of all these fibers?
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If you have damage at that level, you will have massive hemiparesis (and loss of sensation too), but if you get it further up, you will only lose some function.
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What tends to go wrong pathologically at this convergence area for the motor and sensory fibers?
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ischemia of the lenticulostriate arteries
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Draw the transection of the top of the midbrain. Include the substantia niagra.
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Why are there eyes on top?
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That is the superior colliculus, which is part of the tecta which are EYES because they regulate the visual reflex!
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Give an example of the spinovisual reflex?
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You step in mud and you immediately turn your eyes to look at it.
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Give an example of the visual-spinal reflex?
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you see a ball coming at you and you
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Why is the substantia niagra named what it is?
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Because it is a black substance.
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What disease does damage to the sbstantia niagra result in?
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Parkinson's.
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Draw the 3 different sections of the transection of the midbrain.
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Now label each part.
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Show which part the cortical spinal tract goes through the midbrain. Does it go through this whole part?
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What happens to the motor neurons in the pons?
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Some get dispersed by the pontine nuclei and then converge again at the medulla.
Others terminate on the pontine nuclei and go to update the cerebellum. |
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What are these motor fibers terminating in the pons called? Why?
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cortical pontine fibers. (for where they originate and end)
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Draw what the motor pathway from the cortex to the cerebellum look like.
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The pontine nuclei send all the descending motor info posterior to the cerebellum.
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What happens to the cortico-spinal motor neurons in the pon?
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They get dispersed by all the pontine nuclei and then reconverge again.
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If you get a lesion in the pons, how much motor loss will you get? Why?
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Only some because they are spread out.
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Show where the motor corticospinal tracts pass through the medulla? (transection) What are these tracts called?
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Show where the pyrimidal motor tracts cross. What is this called?
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How many of the fibers decussate here at the Junction of medulla and spinal cord?
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90%
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What are the 10% that don't cross?
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The medial 10% which will control axial muscles like the trunk.
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What are the tracts that haven't crossed at the motor crossing called? Why?
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Ventral or anterior descending motor tracts because they go through the anterior columns.
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What are the tracts that have crossed at the motor crossing called? Why?
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lateral descending motor tracts because they go through the anterior columns.
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Will all of these motor neurons terminate at an alpha motor neuron?
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Only the 3% that are from Betz cells. The rest will go through a internunchal neuron (interneuron).
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Show where the cell bodies for the axial vs appendicular alpha motor neurons are.
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Where are the neurons that terminate in the medial anterior horn from? Why?
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The supplemental motor cortex because they are more primitive motions!
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When do the axial motor neurons decussate? Mnemonic?
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The the level of their alpha motor neuron. They are those AX-holes that swerve off the interstate at the last minute to their exit.
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Show the path of the motor neurons from the cortex to their exit points.
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So overall, what is the point of making a lot of motor collateral connections in the brain?
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It informs other parts of the brain about what it plans to do so they can support the movement!
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Show the collateral neurons given by the descending motor neurons and where they send the signals to. (6)
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Can you list all 6 of these structures?
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1. Motor cortex 2. Lenticulate nucleus
3. Reticular formation 4. Red Nuclei 5. Vestibular nuclei 6. Olivary nuclei |
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Why send collaterals of the motor fibers to the motor cortex? (Mnemonic?)
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So it knows what you have decided to do. (Like telling your wife you are leaving the house)
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Why send collaterals of the motor fibers to the lenticulate nucleus?
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It's part of the basal ganglia and will help with execute the movement by providing background tone.
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Why send collaterals of the motor fibers to the reticular formation?
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It will wake up the cerebral cortex so you can pay more attention to what you are doing?
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What implication does this have for exercise's effect on your alertness?
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Going for a jog will increase your brain capacity on a physical neurological level.
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Why send collaterals of the motor fibers to the red nucleus? What functions does it help with?
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this is where you will control wrist tone which will help execute functions like writing.
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Why send collaterals of the motor fibers to the vestibular nuclei?
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They are antigravity muscles that make sure you don't fall while executing the function.
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Why send collaterals of the motor fibers to the olivary nuclei?
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They will inform the cerebellum of your plan so it can integrate that with it's information about where your body is and compare that with what happens.
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What is a lower motor neuron?
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Neurons that come out of the CNS and terminate on a neuromuscular junction.
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So are preganglionic, S, and PS neurons considered lower motor neurons?
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NO! Because they end on a ganglion.
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Can lower motor neurons only come out of the CNS from the spinal cord?
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No, they can also come out of the brainstem.
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What is the definition of an upper motor neuron?
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All the neurons that come from the upper level and connect with lower motor neurons and altering their activity (directly or indirectly)
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What are the upper motor neurons that control the cranial nerves called? Why? (Hint, the ones we already learned about are corticospinal neurons)
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Corticonuclear neurons because they terminate in nuclei of the brainstem.
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What are the special corticonuclei in the medulla called?
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corticobulbar
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Draw out the two kinds like corticonuclear fibers.
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Which nerves are lower motor neurons that come from the brainstem and thus the corticonuclear tracts?
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Cranial nerves
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What do the lower colliculi regulate?
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auditory reflexes
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Draw all the neurons that go to the superior coliculi and label them.
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Draw the posterior view of the whole tectum and what functions they serve. (Image mnemonics)
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So if a tract is ascending to the tecta from the spine, where is it going? Why?
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To the superior colliculi because it is the spinotectal tract for the visual reflex. (hearing does come from spine)
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What other sensory fiber goes to the superior colliculi? What other part of the brain are they on their way to?
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sensory info from the eyes which are on their way o the occipital lobe.
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What is the tract that coordinates reflexive muscle movement to avoid a car that you see speeding by called?
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the tectospinal tract.
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Do the tectospinal fibers cross? Where? Mnemonic?
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Yes, they cross at the level they exit (think primitive reflex)
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What are the tracts comiing from the red nucleus called? Where do they cross? Mnemonic?
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rubospinal tracts. In the brain stem (think about it, they support modern hand movements like writing)
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What are the tracts comiing from the vestibular nuclei called?
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vestibulospinal tract
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What are the tracts comiing from the medullary olives called?
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olivaryspinal tract
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Show the locational difference between a upper motor neuron of cortical origin and subsortical origin?
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Draw out a flow chart of the type of motor neurons and which tracts are involved in each. (8 tracts)
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Show which tracts in this flow chart are pyrimidal vs extrapyrimidal.
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What is another name for the corticospinal tracts? Why?
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Pyrimidal tracts because they go through the pyrimids of the medulla.
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Why are the corticonuclear tracts considered pyrimidal tracts?
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they are functionally very similar to the corticospinal tracts (originate from cortex) so they are grouped together even though they don't anatomically pass through the pyrimids.
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Why did scientists find it useful classify tracts as pyrimidal or extrapyrimidal in the past?
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They though pyrimidal tracts were responsible for more advanced motor function and extrapyrimidal for more primitive ones like posture and reflexes.
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Why are we moving away from these terms?
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Because we are discovering that these rules that distinguish the two tracts don't hold true.
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What do you do when a ViP person walks into the room?
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You STAND UP!
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What are the two major groups of muscles in our bodies?
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Flexor and extensor muscles
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What general motions are each group good for?
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extensor- standing up
flexor- sitting down |
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What worldly force do the extensor muscles counter? Why?
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gravity because they help you stand up against it
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What does ViP stand for?
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Vestibule nuclei and Pontine-reticular nuclei
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Draw out how the ViP's help you stand up. (include muscle involved, the column they travel down, and whether or not they cross sides)
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What is the working mnemonic of ViP?
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The vestibulonuclei and pontine-reticular nuclei send fibers down to enhance the tone of extensor muscles to help you stand up.
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How do you remember what column the ViP tracts go down?
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They go down the ipsilateral anterior column because ViPs always go in front and they don't move for anyone!
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Which out of those two standing supportive nuclei help more?
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The vestibulonuclear spinal tract.
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What is the mnemonic for what enhances flexor muscle action?
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Sit on a RUBBER MAT!
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What is the working explanation of sitting on the rubber mat?
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The rubellonuclei and medullary reticular nuclei will send signals to enhance the tone of flexor neurons.
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Draw out how how the rubber mat help the flexor system. (include the column they travel down and whether or not they cross sides)
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Did I get the orientation of the flexors and extensors right in the knee?
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No, I reversed them. Extensors are quadripceps and flexors are hamstrings.
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Draw and lateral view of how these assistant tracts connect. (make sure to get their positions correct and note which cross.
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