Proprioception and Kinesthesia

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Proprioception and Kinesthesia

• Spinal Control of Movement

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Proprioceptive Sensations

• Definition-an awareness of body position and of
  movements of parts of the body.
• Proprioception tells us the location and rate of
  movement of one body part in relation to others.
• Proprioceptive sense informs us of
• the degree to which our muscles are being
  contracted
• the amount of tension created in the tendons
• change of position of a joint
• the orientation of the head relative to the
  ground and in response to movements

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Proprioceptors

• Only slight adaptation-this allows the brain to
  be informed continually of the status of
  different parts of the body so that adjustments
  can be made.
• Receptors for Proprioception
• Muscle Spindles
• Tendon organs
• Joint kinesthetic receptors

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Proprioceptors Contd

• The three types of receptors are located in
  skeletal muscle, tendons, joint capsules and
  within the inner ear.
• Impulses for conscious proprioception pass along
  ascending tracts in the spinal cord to the
  thalamus and from there to the cerebral cortex.
• The sensation is perceived in the somatosensory
  area in the parietal lobe of the cerebral cortex.

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Joint Kinesthetic Receptors

• There are several types of joint kinesthetic
  receptors within and around the capsules of
  synovial joints
• Encapsulated receptors-present in the joint
  capsules and respond to pressure.
• Receptors inside connective tissue-outside of the
  joint capsule and respond to acceleration and
  deceleration of joint movement.

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Additional forms of Proprioception

• Receptors in the joint capsule
• Mechanosensitive neurons
• Angle direction velocity sensitive
• Combine with spindle and GTO, in addition to
  receptors in the skin
• Loss of one or more systems
• Total hip or knee replacement

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Cutaneous Receptors

• There are other receptors related to movement
  perception which are located in various places
  within the skin.
• These receptors can signal sensations to the
  body, such as pain, pressure, heat, and cold.
• For the purposes of this class, these receptors
  are important for movement control because they
  signal information about touch and deep pressure.

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Types of Cutaneous Receptors

• Pacinian Corpuscle-located deep in the skin and
  are stimulated by heavy pressure. Other receptors
  inside the skin Meissner Corpuscles, Merkels
  disks and Ruffinis corpuscles.
• Hair follicle Receptors-located close to hair
  follicle and are stimulated when the hairs on the
  body are deformed by light touch.
• Fingertip Receptors-provide information about the
  surfaces of objects through touch.

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Input to the CNS

• The major pathways for transmitting signals from
  the periphery to the brain are the spinal tracts,
  which are located along the vertebrae.
• Input to the CNS goes through roots that collect
  and guide the information to the spinal cord.
• And the input from the receptors comes together
  in the periphery into spinal nerves.
• Spinal nerves are collections of neurons that
  carry information toward and away from the spinal
  cord.

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Proprioception and the CNS

• Proprioception enables us to tell where our limbs
  are and how they are acting
• The CNS combines and integrates information in a
  way to resolve any ambiguity received by the
  signals from the receptors.

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Proprioception and Motor Control

• The expanded Closed-loop model for movement
  control
• Muscle contractions cause the limbs and the body
  to move, which causes change within the
  environment.
• The contracting muscles and the movement of the
  body produce sensations from the different
  receptor systems.

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Sensory Components of Movement

• Vision
• Horizontal and vertical cue
• Orientation to environment
• Vestibular
• Inner ear
• Head movement and position

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Sensory Integration

• Spinal Cord Level
• Reflexes
• Cyclical Movements
• Higher Brain Centers
• Cerebellum
• Brain Stem
• Motor Cortex

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ROLE OF PRIOPRIOCEPTIVE FEEDBACK

• Affects the degree of movement accuracy
• Influences the timing of the onset of motor
  commands
• Coordinates body and limb segments (to self and
  environment)

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Muscle Receptors
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Sensory Components of Movement

• Sensory Receptors (Mechanorecpetors)
• Joint Receptors
• Joint capsule and ligaments
• Joint position and rate of movement
• Only at extreme ranges of motion

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Sensory Components of Movement

• Sensory Receptors (Mechanorecpetors)
• Muscle Receptors
• Golgi Tendon Organs
• Muscle Spindles

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Types of Spindle Fibers

• Bag fibers
• Chain fibers
• Different fibers are responsible for static
  (chain) and dynamic (bag1) movements

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Physiology of Muscle Spindles
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Proprioception from Muscle Spindles

• Middle section is swollen and contains group Ia
  sensory axons wrapped around spindle
• Sensitive to muscle stretch
• Ia neurons are the largest and therefore the
  fastest sensory neurons in the body
• Enters dorsal horn synapse in the spinal cord
  with interneurons and alpha motor neurons exits
  ventral horn with motor command.

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Muscle Spindles

• Specialized groupings of muscle fibers
  interspersed among regular skeletal muscle fibers
  and oriented parallel to them.
• One Muscle spindle 3-10 specialized muscle
  fibers called intrafusal muscle fibers.
• Surrounding the muscle spindle are regular
  skeletal muscle fibers called extrafusal fibers.
• These fibers contract when stimulated by small
  neurons called gamma motor neurons.

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MUSCLE SPINDLE

• Why do muscle spindles contain their own
  contractile elements?

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MUSCLE SPINDLE
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Muscle Spindles Contd

• Muscle spindles monitor changes in the length of
  a skeletal muscle by responding to the rate and
  degree of change in length.
• This information is relayed to the cerebrum,
  which allows conscious perception of limb
  position.
• Also, passes to the cerebellum to aid in the
  coordination and efficiency of muscle contraction.

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MUSCLE SPINDLE
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MUSCLE SPINDLE
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MUSCLE SPINDLE
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Muscle fiber vs. Muscle spindle

• Skeletal muscle
• Extrafusal fibers
• Alpha motor neuron
• Activation causes muscle to contract
• Function
• Shorten or lengthen to cause or control movement
• Contraction occurs from cortical drive or muscle
  spindle activation

• Muscle Spindle
• Intrafusal fibers
• Gamma motor neuron
• Activation causes muscle spindle to reset
• Function
• sense changes in muscle length
• Provide moment to moment control of movement

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Alpha-Gamma Coactivation

• Simultaneous activation of Alpha and Gamma motor
  neurons
• Alpha shortens the muscle
• Spindle would become slack and unable to sense
  further stretch
• Gamma motor neuron keeps spindle taught and able
  to sense movement
• During this simultaneous contraction possible
  decreased sensitivitywhy?
• Movement Detection
• Contracting muscle 2.4 times larger movement
  required

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GTO
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Golgi Tendon Organs

• Function as a strain gauge, measuring tension in
  the muscle
• Situated in series with muscle fibers
• Located close to the tendon's attachment to the
  muscle
• Information carried via Ib neurons
• Enter spinal cord synapse on interneurons, and
  inhibitory neurons
• Even senses small changes in tension
• Inhibit contracting (agonist) muscles and excite
  antagonist muscles to prevent injury
• Sensory (afferent) Type Ib fibers penetrate the
  tendon organ capsule.

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Golgi Tendon Organs

• Can protect from overload, or regulate
  contraction in optimal range
• They also function as, contraction receptors by
  monitoring the force of contraction of associated
  muscles.
• Important for fine motor control
• Help to maintain optimal contraction force to
  manipulate fine objects

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Golgi Tendon Organ
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GOLGI TENDON ORGAN
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GOLGI TENDON ORGAN
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Sensory Motor Integration

• http//www.learner.org/resources/series142.html

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CPGs
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Central Pattern Generators

• Rhythmic movements can be controlled by the SC
• Following an initial stimulus to start, the CPG
  can cause alternating bursts of activity
• Higher brain centers can intervene if adjustments
  are needed
• Gait patters are possible without higher brain
  centers

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CPGs
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CPG cntd.

• The CPG is under influence of loosely defined
  higher brain center and also receives inputs from
  peripheral sensors and possibly other structures.
• Afferent inputs into a CPG may bring about
  changes in the pattern of its activity, leading
  to changes in gait.

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Locomotor Centers

• In the 1960s a group of researchers in Moscow
  stimulated the reticular formation of the
  midbrain of decerebrate cats.
• Stimulation of certain areas led to rhythmic
  locomotor-like movements of the cats limbs.
• The frequency of the stimulation was not related
  to the frequency of locomotion, so it was assumed
  the CPG is activated by descending signals
  generated by the stimulation.
• An increase in amplitude led to an increase in
  locomotor speed, eventually leading to a change
  in gait.

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Decerebrated Cat
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Would locomotor movements such as walking,
trotting, and galloping require different CPGs?
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Control of Locomotion

• What benefit comes from CPGs?
• Think in terms of control requirements!

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Spinal Locomotion

• If the spinal cord of an animal is cut acutely, a
  locomotor pattern is typically observed for a few
  seconds.
• This is best explained as a release of the
  activity of a spinal CPG from the tonic
  descending inhibitory influence.
• A chronic spinal animal will not display
  locomotion without external stimuli, but will
  when placed on a treadmill display stepping of
  the limbs with shifts in gait to alternating
  speeds.
• Spinal locomotion is observed in animals in which
  all of the dorsal roots have been cut (without
  afferent inflow), proving the spinal cord capable
  of producing movement without feedback.

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Spinal Locomotion cntd.

• It has also been demonstrated that individual
  CPGs may exist for each limb.
• Recent data have suggested a spinal locomotor
  generator located at a lower thoracic-upper
  lumbar level in humans.
• Patients will display involuntary stepping
  movements of the legs, when unable to do so
  voluntarily.
• Although coordinated locomotor activity is
  displayed, the movements are not meaningful for
  many reasons.
• The animal needs information about the
  environment, control of posture, and needs to
  handle perturbations.

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Interneurons
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Spinal Interneurons

• GTOs action on alpha motor neurons is
  polysynaptic (what was the spindles synapse?)
• Interneurons receive input from
• Primary sensory axons
• Axons from the brain
• Collaterals of lower motor neuron axons
• Interneurons are interconnected allowing for
  coordinated movement of multiple spinal levels

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Reciprocal Inhibition

• Muscle is stretched Ia neuron synapses with
  alpha motor neuron stretched muscle contracts
  what is missing from this?
• Now what about a voluntary contraction?
• Biceps contracts tricep stretches tricep
  spindle stretches causing tricep to contract
• If this happened would we have smooth movement
• Descending command also tells antagonist to relax
  via interneurons

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Flexor Crossed-extensor reflex

• Interneurons can also facilitate contractions
• Response to adverse stimuli
• Flexors of affected limb contract
• Reflex is slower that myotatic necessitating
  interneurons
• Response also involves extensors of opposite limb
  to contract
• Building block for locomotion
• Central pattern generator

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Illusory Movement

• Perceptions of movement or movement mismatch can
  occur
• Efferent/control process illusion
• Distorted signals from receptors, or processing
  of afferent signals
• Muscle vibration creates a distorted signal, and
  causes the spindle to fire repeatedly appears
  that muscle has lengthened
• Distorted efferent copy signal
• Commands that differ from what was expected by
  the brain

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Remote Controlled Human???
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Purpose

• What effect do illusory changes in head position
  have on joint position sense in the elbow
• Novel in that they were not using any
  biomechanical changes in muscle length

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Vibration effects

• What is the general feeling with muscle vibration
  in general
• Feeling that the muscle in lengthening
• What is the general feeling with galvanic
  vestibular stimulation?
• Lateral body tilt toward the anode
• What was the result of low GVS stim?
• Postural shift but no changes in head position
  sense
• Increased GVS resulted in head shift sense
• Sense is away from but sway is towards the
  anode??? What Page 94 vs. 97

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Results/Discussion

• Significant difference in reporting Joint angle
  in mid range of movement
• Why not extremes?
• How is this related to integration and movement?
• What implication were made based on this study to
  perception and action coupling?
• Position of the head plays an important role in
  joint proprioception
• Since the head did not move it is more than
  biomechanical changes in head position

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Why were the results inconsistent?

• Most studies showed that individuals exposed to
  the GVS will exhibit changes in sensation of head
  position
• What was reported to suggest that something else
  may have contributed to the mixed findings?
• Supine vs. upright

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Off to the Lab!!!