Posture and Movement

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  • Created by: LBCW0502
  • Created on: 16-11-18 14:48
What is movement? (1)
Universal characteristic of living material (historically ancient, evolving from amoeba gracefully extending their pseudopodia, 3500 million years ago). Same body chemical and energy source used. Control of movement is important
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What is movement? (2)
Motor system (complex) - movement requires co-ordinated action of combinations of more than 750 muscles in ever changing and unpredictable environment
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What is posture?
Stable position on which movement is superimposed - need stable posture for movement
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State the features for the physiology of posture
Postural control (static/phasic reflexes). Static - sustained contraction muscles. Dynamic - short term phasic reflexes. Posture (autonomic/unconscious), reflex control/constant shifts, postural sway, myotatic stretch reflexes adjust
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Describe features of reflexes
Integrated at many levels, CNS/spinal cord to cerebral cortex. Primary control - extrapyramidal motor tracts (vestibulspinal). Postural reflex patterns (co-ordination of many joints)
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Outline the monosynaptic reflex arc
Receptor detects stimulus (change in environment). Impulse sent through sensory neurone in dorsal root ganglion and into CNS. Impulse sent through motor neurone in ventral root and impulse is sent to effector (muscle/gland)
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What are the two examples of crossed-extensor reflex
Bicep/triceps and quadriceps/hamstrings
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Outline the mechanism for crossed-extensor reflex
One impulse sent in afferent neurone to spinal cord to produce contraction (e.g. bicep, quadricep) and another impulse is sent through inhibitory interneurone in efferent neurones to prevent contraction (e.g. tricep, hamstring)
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Describe features of alpha-gamma coactivation (1)
Posture control varies excitability, alpha-gamma motor neurones. Changes sensitivity of spinal reflexes. Afferent input sensory ending to muscle spindle fibre. Alpha motor neurone output to regular skeletal muscle fibre. Stretch reflex pathway
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Describe features of alpha-gamma coactivation (2)
Gamma motor neurone output to contractile end portions of spindle fibre. Descending pathways co-activating alpha and gamma motor neurones
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What is postural sway?
Posture dynamic. Pendulum oscillations. Centre of mass circular movements. A-P 7 mms
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Which parts of the brain are involved in higher control reflexes?
Vestibular, visual and joint reflexes - mediated via brain stem
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Vestibular reflexes require what kind of information?
Need information orientation to vertical vestibular apparatus - sense organ. Neural pathway - inner ear - vestibular nuclei - spinal motor neurones - postural reflex body movements (e.g. lean to left, excite extensors on right, recover vertical)
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Describe features of visual reflexes
Powerful input posture control. Neural pathway - eye - lateral geniculate nucleus - midbrain - descending reflex pathways - spinal motor neurones
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What is the function of pressure receptors?
Important receptors for maintenance of posture (e.g. skin pressure receptors, stand soles feet pressure receptors monitor distribution weight) - clinically if destroyed e.g. tabes dorsalis - fall when eyes are closed
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What is cortical control?
Extensive cortical control, learnt control, correction reset, 'norm'
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What are the 3 primary control areas in the brain?
Spinal cord, brain stem and cerebrum
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What are the 2 side circuits?
Cerebellum and basal ganglia
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What are the stages of movement?
Before, start, during, stop, after
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State features before movement
Tone, posture, balance, 3 systems (control feedback) - visual, vestibular, propriception
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What happens during the start of movement?
Initiation of voluntary movement - basal ganglia
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What happens during movement?
Monitoring control messages and actual position. Cerebellum compares signal from cerebrum with that from periphery and detects mismatches, error correction, smooth movement co-activation alpha/gamma
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What occurs when stopping movement?
Requires 'brakes' on before reach goal - basal ganglia and cerebellum. Relies on feedback to predict end point
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What happens after movement?
Return to resting state
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What are the different parts of the brain involved in controlling movement (time sequence)?
Parietal lobe, occipital lobe, frontal lobe, central sulcus, lateral sulcus and temporal lobe - cortex regions e.g. auditory, visual, primary motor etc.
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What is the role of the prefrontal cortex?
Idea, motivation e.g. thirst. Conceptualisation - what is the goal/plan?
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What is the function of the supplementary motor area?
Motor association cortex, secondary motor cortex. Plan strategy, how to achieve goal, programme for movement
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What is the function of the posterior parietal cortex?
Analyses sensory information related to postulated movement particularly visual. Activates supplementary motor area premotor cortex. To plan and write programme for movement
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What is the function of the cerebellum?
Balance, co-ordination, motor memory. Monitors/compares what plan to do (motor cortex command) with what actually happens (proprioceptive feedback) - corrects if there is a mismatch
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What is the function of the basal ganglia?
Amplitude settings, timing sequences, programming. Programme - which muscle contracts and how much. Several nuclei, 2 pathways (direct/indirect)
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What do the supplementary and premotor cortex command?
The primary motor cortex which initiates postural adjustments
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What is the function of the primary motor cortex?
Activate spinal motor neurones via cortico spinal tracts (70% + decussate in medulla). Homunculus - single fasiculus to large muscle groups (diagrams)
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What is the function of the spinal cord?
Activates muscles. Signal arrives anterior horn cell. Anterior root, common peripheral nerve. Muscle synapse (NMJ)
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What is the function of muscle?
Contraction to cause movement (e.g. anatomy, sliding filament model)
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State features of sensory feedback
Visual, vestibular, peripheral - muscles (spindles), tendons (GTO), joints, cutaneous
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Summarise movement control
Cerebral cortex, functional areas, temporal sequence motor control, cerebellum, basal ganglia, sensory feedback (see flow chart for summary pathways)
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What is akinesia?
No movement (supplementary motor area, basal ganglia), difficulty with tasks requiring co-operative movements for both hands, cannot initiate movement
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What is bradykinesia/hypokinesia?
Slow/decreased movement - clinical aspect - PD
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What is apraxia?
(Premotor/parietal cortex) - clumsy/slow movements, mild proximal joint weakness, loss co-ordinated skilled movements, especially proximal joints - clinical - minimal brain dysfunction/'clumsy child'
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What is dysmentria?
(Cerebellum) - wrong distance/inappropriate range movement. Over shooting/under shooting clinical - MS
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What is ataxia?
(Cerebellum) - continual errors through movement
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What is ataxic gait?
Unsteady swaying walk, feet wide apart, cannot toe-heel walk on line - clinical - multiple sclerosis
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What is asynergia?
(Cerebellum) - lack of co-ordination, breakdown of total movement
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What is chorea?
(Basal ganglia) - quick, irregular, involuntary, relatively co-ordinated movements of limbs, trunk, head and face, clinical - Huntington's disease
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What is dystonia (athetosis)?
(Basal ganglia) - slow writhing movements neck/trunk, patterned/repetitive, starts during voluntary movement
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What are tics?
(Lack of dopamine) - abnormal movements or abnormal sounds, simple jerk or complex movement - clinical - Tourette syndrome
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Describe the features of the direct pathway for the basal ganglia
Concerned with initiation of movement - cortex-putamen-GP interna-Va/Vl thalamus (use of glutamate/excitation and GABA/inhibition, GPe/STN). Double inhibition (net result/excitation cortex movement) - dopamine excitation
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Describe the features of the indirect pathway for the basal ganglia
Scenic route - cortex-putamen-GP externa-STN-GP interna-VA/L thalamus (use of glutamate/excitation and GABA/inhibition) - dopamine inhibition
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Triple inhibition results in what?
Net result - inhibition of thalamus and loss of excitation cortex/loss of movement
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Outline the issue with PD in the direct and indirect motor loops
Neither excitation of putamen or inhibition of putamen due to low levels of dopamine (effect on GABA and glutamate) - flow chart diagram
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Card 2

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What is movement? (2)

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Motor system (complex) - movement requires co-ordinated action of combinations of more than 750 muscles in ever changing and unpredictable environment

Card 3

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What is posture?

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Preview of the front of card 3

Card 4

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State the features for the physiology of posture

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Card 5

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Describe features of reflexes

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