PSL440Y1 Lecture Notes - Motor Learning, Globus Pallidus, Proprioception

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erincheetah56

8 Jun 2012

School

UTSG

Department

Physiology

Course

PSL440Y1

Professor

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The central motor system is arranged as a hierarchy of control levels, with the forebrain at the top and the spinal cord at the bottom (see table 14. 1). The highest level concerned with strategy the goal of the movement and the movement strategy that best achieves that goal. The middle level is concerned with tactics the sequences of muscle contractions, arranged in space and time, required to smoothly and accurately achieve the strategic goal. The lowest level is concerned with execution activation of the motor neuron and interneuron pools that generate the goal-directed movement and make any necessary adjustments of posture. The proper functioning of each level of the motor control hierarchy relies so heavily on sensory information that the motor system of the brain might be considered a sensorimotor system. At the highest level, sensory information generates a mental image of the body and its relationship to the environment.

Related Questions

An important question to consider when thinking about globalwarming is, "If the ice sheets near the poles melt, how much willthe sea level rise?" This seems like a difficult question, giventhe odd shapes of both the ice sheets and the oceans. But there aresome accurate approximations that allow the answer to be estimatedfairly accurately with reasonably simple calculations.

The critical idea is that both the thickness of the ice sheets andthe amounts of the sea-level rise are extremely small compared tothe radius of the earth. The radius of the earth is about 2/p x 107m -- more than 6000 kilometers. The ice sheet thicknesses we willbe concerned with are single digit miles and the sea level riseswill be in dozens of feet. As a result, in thinking about them, wecan essentially ignore the curvature of the earth. We can imaginepeeling the map of the earth off a globe and flattening it out (bymaking cuts, not by stretching it, so that we preserve the area).Then, both the ice and the sea level rise can be treated as right(not tilted) cylinders (though with funny shaped bases and tops).Since we know that the volume of a right cylinder is the area ofthe base times the height, we can easily estimate all the volumeswe need. A schematic picture of this approximation (with the heightof the ice mass greatly exaggerated -- you couldn't see it if Ididn't) is shown below. The error in these approximations is on theorder of the height of the cylinder considered divided by theradius of the earth; a very small number.
a. Assume that (after flattening the surface of the earth in ourimaginations) the ice sheet to be considered covers an area, A, andhas a thickness, d. The oceans currently cover about 75% of theearth's surface, and note that the surface area of a sphere is 4pr2where r is the radius of the sphere.

Generate an equation that will allow you to calculate h, the heightthe ocean levels will rise due to the melting of a an ice sheet interms of A, d, and r

b. As shown in the combined satellite photo on the right (fromGoogle Earth), Greenland is covered by a sheet of ice. This ice hasbeen measured to have a mean thickness of about 2 km. Recentobservations indicate that this ice sheet is beginning to retreat-- that it is melting at an accelerating rate.

Using the depth of the ice sheet and the scale given on thepicture, estimate how much sea level rise would be produced by themelting of the entire ice sheet lying on Greenland. (Note: You caneasily look this information up on the web. But the goal of thisproblem is in part to develop your estimation skills for thepurpose of building your ability to decide for yourself whether anygiven piece of information you find on the web is reasonable orbogus.)

Theory: Topics that you should be familiar with are: significantfigures, least count and estimated fraction, systematic and randomerrors, accuracy versus precision, percent difference and percenterror. These topics should have been covered in class already (orperhaps in an introduction to the lab manual or in a handout). Itis assumed that the instructor has discussed how to use the massbalance, etc.
Introduction: The goal of section I of this experiment is tomeasure (to the correct least count and estimated fraction) andcalculate (to the correct number of significant figures) thedensity of a metal ball and compare it to a table of accepteddensities (?=7.8x103 kg/m3).
To accomplish this goal keep in mind that: ? = m/V and Vsphere =(4/3) p r3
In the space below create a data table, show your calculations indetail, and compare your measured answer to accepted values givenabove. (Would you calculate a percent error or a percentdifference?)
1
II. Is g (the acceleration due to gravity) a constant? If so, whatis it?
1) SetuptheFree-FallApparatusasdemonstratedbytheinstructor.
2)MeasurethetimeittakesforthemetalballtofallthroughthesuggesteddisplacementsshowninDataTable 1. Be sure to do 4 trials for each fall and take the averageof your time and displacement. For each trial measure thedisplacement and record your results as precisely as possible. Becareful how you measure the displacement!
Data Table 1
Displacement (meters) Time
Trial 1
___.40___ m .281 s
______.40_ m .284 s
___.40____ m .283 s
____.40___ m .285 s
Average Displacement =.40 m Average time .0285 s
Trial 2
____.60___ m .357 s
____.60___ m .358 s
_____.60__ m .347 s
____.60___ m .347 s
Time (seconds)
Average Displacement = .60 Average Time = .352
Trial3
_.80____ m .402 s
_.80____ m .401 s
_.80______ m .402 S
_.80___ m .401 s
Average Displacement = .80 m Average Time =.401 s

Trial4
__ 1.00____ m .454 s
___1.00____ m .453 s
___1.00____ m .463 s
___1.00____ m .453 s
Average Displacement = 1.00 m Average Time =.455 s
3)PlotDisplacement(usetheaveragedisplacement)asafunctionofTime(usetheaveragetime)usingacomputer software that you know the best. (Does Displacement orTime go on the âverticalâ (or y) axis? Make sure that you label theaxes of your graph properly and give the graph a descriptivetitle.), Please include (0,0) point.
4)UsetheCurveFitFunctiontotrytofindthecurvethatistheclosestfitforthegraph.Whichofthefollowing curve types gives the best fit? Try each to findout.
a) linear fit? b) quadratic (power 2)? c) exponential? d) Power?
The curve with the correlation coefficient (R) closest to 1 has theclosest fit. (e.g. 0.997 is better than 0.956)
5)Printthecurvewiththeclosestfit(oneforeachmemberofthelabgroup).Besureyourgraphincludesthe equation for your fit.
6)Canyoudeterminetheexperimentalaccelerationofgravityfromthisgraph?Explainhowandshowyourwork.
7)Ifalinearfunctionisnotthebestfitofyourplotfromstep3),howwouldyouplotdisplacementandtimeso that the resulting plot is linear? Explain. (Ask your instructorfor a hint if you are not sure of what to do, but be sure to thinkabout it for a while before you ask.)
3
8)Printacopyofthegraphforeachlabpartnershowingalinearfittoyourdataandproperlylabeledaxes.
9)Canyoudeterminetheexperimentalaccelerationduetogravityfromthisgraph?Explainandshowyourwork.
10) How do your experimental values of âgâ compare with theaccepted value (g = 9.80 m/s2) for the acceleration of gravity?Give a mathematical comparison using what you learned aboutmeasurements previously. (Show work)
4
Question and further procedures
1. What is the greatest source of error in performing theexperiment? Is this error random or systematic? Explain.
2. At this point you should have calculated g in two different ways(A quadratic graph, and a linear graph). Which technique do youthink is best? Do all two techniques give the same answer? If not,which technique do you think has the most error?
3. How might you modify your procedures to determine whether or notg depends on the mass of the falling object? Do the experiment andcalculate g using your favorite technique.

MAC, Inc. (the company you work for) has decided to move forwardwith a feasibility
study for a product it wishes to manufacture and sell. This productis a particle launcher that should have the capability, for everyactivation, of launching two particles into the air at twodifferent times and at two different angles of elevation, in anautomated fashion so that they both land at the same distance fromthe launch point at the same time. For example, let P1 and P2 betwo particles, let T1 and T2 be two times, and let theta1 andtheta2 be two angles of elevation. Once activated, the launchershould be able to operate so that particle P1 is launched at timeT1 with an angle of elevation theta 1, and particle P2 islaunched
at time T2 with an angle of elevation theta2.
The launcher must be configured by a technician, prior to eachactivation, so that the
initial speed is set for the launcher, and the distance from thelauncher to where both
particles will land is set. For each activation of the launcher,the initial speed will be the
same for both particles. Once the technician has set the initialspeed and desired distance,
the launcher must calculate the angles of elevation to use and howmuch time to wait in
between particle launches. Then, when the technician activates thelauncher, both
particles will be launched at the appropriate angles of elevationand at the appropriate
times so that they both land at the configured distance from thelauncher at the same time.
The launcher, based on its calculations, will change the angle ofelevation to be ready for
the second particle launch. The launcher, however, must flash awarning for the
technician if the information the technician used to configure thelauncher does not result
in a two-particle launching solution.
Certain assumptions must be made. It is assumed that that launchercan always change
the angle of elevation to get ready for the second particle launchfaster than the time
delay calculated for the second particle launch. It is assumed thatthe units for speed are
meters per second, that the units for distance are meters, and thatgravity is 9.8 meters per
second squared. It is assumed that gravity is the only force actingon the motion of the
particles after launch, and that there is no wind to be considered,so that the particles land
at a point exactly in line with the direction the launcher ispointed.
The questions that must be answered and written up in anengineering report are as
follows:
1. Given the initial speed and desired landing distance for theparticles, find the
mathematical expressions that must be used to find 1, 2, and thetime delay
between particle launches.
2. Determine under which conditions the launcher will not be ableto perform the
operation requested, and will consequently flash a warning to thetechnician.
3. Each particle launched will follow a path of motion that isparabolic. Show that
the vertex of the parabola for each particleâs path occurs at thesame distance from
the launcher.
4. Along the path of each launched particle, there will be amaximum curvature.
Find that maximum curvature for each launched particle.

PSL440Y1 Lecture Notes - Motor Learning, Globus Pallidus, Proprioception

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