electric motion fin
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ackman678
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motor1.md
48
motor1.md
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## Movement
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* Movement is the planning, coordination & execution of a motor program that relies on information provided by the sensory system
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* Movement is controlled by the motor systems of the brain and spinal cord
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* Movement is controlled by the motor systems of the spinal cord and the brain
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* Motor systems translate neural signals into contractile force in muscles
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* Allows us to maintain balance and posture, move our body, limbs, eyes, tongue & communicate through speech
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@@ -79,7 +79,8 @@ Note:
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* Each muscle fiber is innervated by only one motor neuron. Group of muscle fibers in a muscle innervated by a single motor neuron is a motor unit
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* twitch happens after small small latency, 5-10 ms
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TODO: motor neuron AP --> muscle fiber EPP --> muscle fiber AP. AP and Vm in muscle fiber, latency, and muscle tension rise and decay
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todo: motor neuron AP --> muscle fiber EPP --> muscle fiber AP. AP and Vm in muscle fiber, latency, and muscle tension rise and decay
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---
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@@ -190,7 +191,7 @@ motor unit
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* motor unit in soleus (important for posture) has ~180 muscle fibers/per motor neuron
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* gastrocnemius has large and small motor units with 1000-2000 muscle fibers per motor neuron. Generates forces for sudden changes in body position.
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* extraocular motor units very small (~3 fibers/unit). High proportion of fibers that can contract at max velocity
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* but lots of use dependent motor unit plasticity (atheletes, hypogravity conditions)
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* but lots of use dependent motor unit plasticity (athletes, hypogravity conditions)
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<!--
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motor unit in mouse skeletal muscle
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@@ -375,12 +376,12 @@ Ia afferent activity
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II afferents
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: innervate static nuclear bag fibers and nuclear chain fibers
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: signal sustatined fiber stretch by firing tonically, little dynamic sensitivity
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: signal sustained fiber stretch by firing tonically, little dynamic sensitivity
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: muscle tone
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There are also dynamic and static classes of gamma momtor neurons
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There are also dynamic and static classes of gamma motor neurons
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helps form negative feedback loop
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The muscle spindle helps form negative feedback circuit through its connectivity with spinal neurons.
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--
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@@ -468,7 +469,9 @@ But the infrafusal muscle fibers are muscle-- why not just have the muscle spind
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Need to adjust the muscle spindles so that they can provide useful feedback across a range of muscle lengths.
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Provide gain to keep muscle spindles active at all lengths.
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Think about your big guns you use to hold that glass of oktoberfest... changing length of biceps
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piezo1 and piezo2
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<https://pubmed.ncbi.nlm.nih.gov/20813920/>
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---
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@@ -553,9 +556,11 @@ Note:
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Note:
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## Muscle reflexes: response to load and overload
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<!-- <div><img src="figs/13-06_MuscleReflexes_L_8cefd3d.jpg" height="100px"><figcaption></figcaption></div> -->
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<!--
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Muscle reflexes: response to load and overload
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<div><img src="figs/13-06_MuscleReflexes_L_8cefd3d.jpg" height="100px"><figcaption></figcaption></div> -->
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---
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@@ -589,15 +594,12 @@ Note:
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---
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--
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## Flexion reflex video summary
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<div><video height=400px controls src="figs/Animation16-02TheFlexionReflex_OC.mp4"></video><figcaption>Neuroscience 5e Animation 16.2</figcaption></div>
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Note:
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---
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@@ -636,7 +638,9 @@ Note:
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* Defects in spinal cord connectivity interrupt pattern generation
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* [cell article](http://www.cell.com/action/doSearch?searchType=quick&searchText=locomotion+eph&occurrences=all&journalCode=&searchScope=fullSite&contentType=video&startPage=)
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* activating the mesencephalic locomotor region can trigger locomtion and change speed of movement by amount of input to spinal cord. Transection at thoracic level will still allow for coordinated locomotor movements. But not just a stretch reflex, due to CPGs present for each limb. These are all connected together in spanning circuits. Transection not allow for good walking in humans though-- maybe bipedalism requires more upper motor neuron control because of greater postural control requirements...
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* Activating the mesencephalic locomotor region can trigger locomtion and change speed of movement by amount of input to spinal cord.
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* Transection at thoracic level will still allow for coordinated locomotor movements. It is not only a stretch reflex, because there are CPGs present for each limb. The CPGs are all connected together in circuits spanning spinal cord segments.
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* However human locomotion requires more descending input from the brain-- Transection would not allow for good walking in humans-- perhaps bipedalism requires more upper motor neuron control due to the greater postural control requirements
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---
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@@ -652,10 +656,14 @@ S Grillner, P Zangger. On the central generation of locomotion in the low spinal
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## Central pattern generator circuit model for swimming
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<div><figcaption class="big">Lamprey</figcaption><img src="figs/Lamprey_anatomy_5f701d1.png" height="100px"><figcaption>[CC0](https://en.wikipedia.org/wiki/Lamprey)</figcaption></div>
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<div><figcaption class="big">Lamprey</figcaption><img src="figs/Lamprey_anatomy_5f701d1.png" height="100px"><figcaption>
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[CC0](https://en.wikipedia.org/wiki/Lamprey)</figcaption></div>
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<div><figcaption class="big">Simplified lamprey CPG model. E, excitatory; I, inhibitory; M, motor neuron
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</figcaption><img src="figs/lamprey-spinal-cpg-model_a1862d9.svg" height="300px"><figcaption>J. Ackman, [CC0](https://wiki.creativecommons.org/wiki/CC0). Based on Grillner et al., *Brain Res Rev* 2008</figcaption></div>
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</figcaption><img src="figs/lamprey-spinal-cpg-model_a1862d9.svg" height="300px"><figcaption>
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J. Ackman, [CC0](https://wiki.creativecommons.org/wiki/CC0). Based on Grillner et al., *Brain Res Rev* 2008</figcaption></div>
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<!--
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@@ -671,9 +679,6 @@ E, extensor. F, flexor. Arrows, excitatory. Closed circles, inhibitory
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Note:
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TODO: add midline, interneuron labels to svg file.
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TODO: add neurons for more complete model representation
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TODO: make model with flexor/extensors for vertebrate locomotion
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lamprey
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: ancient vertebrate
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@@ -686,3 +691,8 @@ spinal locomotor and brainstem respiratory CPGs (Yuste et al, Nat Rev Neurosci 2
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: have an 'excitatory core' of mutually excitatory interneurons
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: ea. hemisegment of the spinal cord has this a core
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: reciprocal inhibition between contralateral hemisegments results in alternating left–right motor output
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todo: add midline, interneuron labels to svg file.
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todo: add neurons for more complete model representation
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todo: make model with flexor/extensors for vertebrate locomotion
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