EXSS 380 Exam 2 Class Notes PDF

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Download EXSS 380 Exam 2 Class Notes PDF

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Class Lecture: Thurs (10/26) LPr e c o r d I nv a r i a ntf e a t ur e s 1 . Or d e ro fe v e nt s r e c o r d e d—o r de ro fe v e n t sd o e sNOTc h a n g e( a l wa y st hes a me ) 2 . Ph a s i n g %r e ma i n st h es a me ;a b s o l u t ev a l u ema yc h a n g e 3 . Re l a t i v ef o r c e Re l a t i v ed i ffe r e nc es t a y st h es a me

Pa r a me t e r s 1. overall duration 2. Overall force 3. Muscle selection

Class Lecture (10/31): Locomotion Locomotion  Movement of ‘yourself’ (one place to another)  Defined by: a ‘rhythm’ o Different muscles have different sequences Central Pattern Generator (CPG)  Rhythmic motor activity (on/off) in sequence o Absence of sensory info  Walking, running, breathing = ‘rhythmic motor systems’ (hard to differentiate when activity starts)  CPG gait/location—neuronal pattern is generated at the Spinal Cord Locomotion (‘The Gait Cycle’)  Stance phase (60%)—extensors active o Heel strike (initial contact w/ ground)  Dorsi flexors on  Knee extensors on o Foot flat  Knee extensors on o Mid-stance  Knee extensors on o Push-off  Plantar flexors on  Swing phase (40%)---flexors active o Acceleration  Knee flexors on o Mid-swing  Dorsi flexors on o Deceleration  Knee extensors on Central Pattern Generators 1. Study of Spinal preparation (ablate to spinal cord; no sensory info to brain)  Spinal cord transection o Brain can NOT communicate with the spinal cord anymore  (Cat in harness) Treadmill walking  still shows Rhythmic stepping o Responsive to speed changes o No input from brain  External stimulation = treadmill  Dorsal roots in tact 2.

Study 2: Electrodes (electrical stimulation) of spinal cord  Stance phase; swing phase (gross flexor and extensor activity)  Generates reciprocal flexor/extensor activity (motor out, even without info from dorsal root) o Reciprocal EMG activity  Rudimentary flexor/extensor (but, unable to normally walk and stand up)  Electrical stimulation producing tonic stimulation in the spinal cord causing rhythmic activity (even without input from brain and sensory info. from dorsal roots) o Evidence that there is something in spinal cord (turn ‘on’) is to produce this rhythmic pattern  ‘Stimulator’ is replacing the brain [Stimulation = electrodes]

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No connection between brain and spinal cord No inputs from dorsal root

‘Generator’—off  No walking; on  walking  Usually, turned on voluntary (top-down control)  When it gets stimulated, the generator will still produce the rhythmic activity (even if there is no input from the brain) Central Pattern Generators  Descending drive necessary for ‘initiation’ and ‘adaptive’ control of CPG o Motor cortex; Cerebellum; Brainstem centers---show rhythmic activity during locomotion  Supraspinal functions [Brain] 1. Initiation (when do you start walking?) and speed control (how fast are you walking?) 2. Movement refinement (via: proprioceptive input) a. What does my gait pattern actually look like? 3. Movement refinement (via: visual input) a. Obstacle notification Descending control: Initiation and speed control  Stimulation of brainstem  stepping movements (reciprocal motion; persists even if sensory info. is taken away in the dorsal roots) o Rhythmicity INDEPENDENT of stimulus pattern (frequency)  Either ‘On’ or ‘Off’ o Gait speed DEPENDS on stimulus amplitude (intensity)  E.g. increasing stimulus intensity causes walking  trotting  galloping  Gait speed changed o Slow walk: contralateral limbs out of phase (right limb vs. left limb) o Peaks are MORE in line as intensity of stimulation increases  Galloping: contralateral limbs in phase  Both are in flexion, or both in extension  Role of Motor Cortex o Experimental lesions:  Still have ability to walk on smooth surfaces  Impaired ability to complete movements that require visuomotor coordination  Deviation from normal pattern  Upper motor can be turned on--but there is no connection between UMNs and LMNs, thus muscles can not turn on to overcome the obstacle o Ramp up of muscle activity of the same pattern, when you have to step over an obstacle  Requires visuomotor coordination  Motor cortex evaluates the sensory information, and then sends out motor commands to make the specific movement to overcome the obstacle  Role of Cerebellum o Input about activation status of CPG and the outcomes of those CPG activation o Important for timing and intensity o Experimental Lesions (‘Cerebellar Ataxia’)  Still do the task, but no feedback  No smooth movements  Inability to ‘refine’ Influence of sensory input on CPGs 3 sources of sensory info: 1. Somatosensory (proprioception, touch) 2. Visual input 3. Vestibular apparatus (inner ear—balance; direction of movement; acceleration)

Receptor-specific roles  Somatosensory receptors  Exteroreceptors o Change in walking in response to external environment (e.g. walking over an obstacle) Spinalized Cats  When the treadmill is turned on, stepping is intitiated  Rate of stepping matches the treadmill speed (external environment cues)  Walking  trot  galloping (based on INCREASING treadmill speed) o Exhibits multiple gait patterns (even without input from the brain) W/increase in stepping speed:  Decrease in stance phase  Swing phase stays constant Stretch hip flexor (pulling on detached hip flexor) - Change in reflexive pattern o Thus, Bend your knee  knee flexion occurs 

Proprioceptive input initiates: ‘Swing Phase’ (knee flexion)

Role of Exteroreceptors  Altering swing phase o Increase in flexor motorneuron activity  Altering stance phase o Increase in extensor activity

Class lecture (11/2): Locomotion (continued) Quadruped vs. Bipedal (human) locomotion  4 limbs  2 limbs (humans) o Thus, significant increase in postural stability muscles Spinal treatment: Electrical Stimulator  Placed in the spinal cord—helps to move legs (in paralyzed individuals)  Evidence of gait CPG in humans  Hip extension  produces rhythmic lower extremity movement in spinal cord-injured individuals  Infants produce rhythmic stepping movements (if held up)  As hip goes into extension  reflexive activity (stepping reflexive activity)  Later on, purposeful movement of walking (better postural control); does NOT require external support

Postural Control Postural control  Maintain upright position  Standing/walking—ability to maintain total body COM within the base of support  ‘Base of support’ (the total surrounding area around the feet)  More stable when your feet are further apart—‘wide stance’ (b/c greater base of support) Postural control 1. Static Postural Control 2. Semi-dynamic postural control 3. Dynamic postural control (e.g. ‘walking’)—you lose ‘base of transport’ (of lifted foot), and transfer everything onto the other foot (foot on the ground) Visual ***most restrained w/o visual input (task becomes much hard without vision) - Postural control depends a lot of vision Somatosensory Vestibular: head linear acceleration; head rotation Postural Control (dependence on visual input)  Conflicting information  Relative motion between cars [‘illusion of motion’] o Visually gained perspective that you are moving (b/c other car is moving); vestibular does not agree  Tendon vibration o Achilles—sensation that muscle is lengthening (change in muscle length)  Lean forward  Postural sway—  COM moving in different directions—thus, there are constant small adjustments we are making to prevent swaying  Postural sway increases when visual input is gone Postural Control (Somatosensory input)  Postural sway increases w/ different somatosensory information o Foam support surface  Softer surface—different info. than hard surface (ground)

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Vision and vestibular are consistent—no changes  Vision and vestibular senses indicate you are moving forward  Ankle receives conflicting info.—still @ 90 degrees, due to depression of foam surface Tendon vibration Joint injury (tendon strain; muscle strain)  Inappropriate somatosensory information  E.g. ‘ankle-strain individuals’—injury to receptors, thus may influence the somatosensory input

Class Lecture (11/7) POSTURAL CONTROL LECTURE The Vestibular Apparatus  What is our head doing in space? (rotation, linear acceleration, static position) Anatomy 

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Otolith organs: linear acceleration (head moving forward in space) o Saccule: sagittal plane (up-down) o Utricle: transverse place (left- right) Semicircular canal: rotation (diagonal planes)

Otolith organs and semicircular canals  Gelantinous fluid: even after the movement, there is still slight movement of the fluid On top of gelantinous matrix  otolith  Static position information---laying down  Linear acceleration Semicircular canals (associated w/rotation) The vestibular apparatus (diagram)  Horizontals are in the same plane  Right anterior + left posterior  Right posterior + left anterior Vestibulo-occular reflex  Response in the eyes to accommodate vestibular movement  Linking eye movement and head movement Postural Control  [Sensory Organization Test] 6 tests (gradually taking away sensory info, or providing incorrect info.) o Even if you are not pathology, it is expected that people will get worse  Test position 1: they are not moving, feet not moving, surround not moving (appropriate vestibular, visual, and somatosensory input)  Test position 2: remove visual ability (blindfolded)—still receive vestibular and somatosensory  Test position 3: Appropriate somatosensory info. and vestibular suggest you are moving; ‘sway-reference’ (if you move forward, environment moves forward) = incorrect visual info.  Test position 4: vestibular info. and visual info., incorrect somatosensory information  Test position 5: no visual input, somatosensory is moving  Test position 6: somatosensory and surround move; improper visual info. ***Ways to tease things out—remove different info/incorrect info.  Diabetes: somatosensory impairments

Applications  Training o Dancers vs. Control  Dancers = larger ‘sway-envelope’ (more comfortable moving)  Aging o Elderly vs. Adult vs. Young Adult  Reduced visual, vestibular, somatosensory (as you age) o Supine-to-standing (transition changing: seating  standing)  Elderly unable to control motions as well (studder-steps) = dynamic base of support (making a new base of support) Aging   

Muscle changes: weaker (weakness of muscles), generate force much slower (inability to generate force quickly) Falling  sharp decline in function Decline in corrective postural responses...