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Postural reflexes

Postural reflexes are the group of reflexes (automatic movements) which maintain body position and equilibrium either during rest or during movement kinetic by changing the distribution of MT in the limbs and trunk. They maintain posture, balance and fluidity of movement, replacing the Primitive Reflexes in a sequential manner, as those Primitive Reflexes inhibit. Righting reflexes are any of various reflexes that tend to bring the body into normal position in space and resist forces acting to displace it out of normal position.

Reflex integrated in medulla

1. Tonic labyrinthic reflexes

  • Receptors: Otolith organs of vestibular apparatus via vestibulospinal tract
  • Stimulus: Gravity, by change in body position
  • Response: Supine position – maximum rigidity in extensor ; Prone position – minimum rigidity

2. Tonic neck reflexes

  • Receptors: neck proprioceptors
  • Stimulus: Head turned to side
  • Response: Extension of limbs on side to which head is turned, up-hind leg flex, down-foreleg flex

Reflex integrated in midbrain

1. Labyrinthine righting reflexes

  • Receptors: Otholithic organs
  • Stimulus: Gravity
  • Response: Head is kept at level

2. Body on head righting reflexes

  • Stimulus: Pressure on side of body exteroceptors
  • Response: Righting to head

3. Body on body righting reflexes

  • Stimulus: Pressure on side of body exteroceptors
  • Response: Righting of body even when head is prevented to right

4. Body on neck righting reflexes
Stimulus: Stretch of neck muscle
Response: Contraction of neck muscles rights thorax and abdomen

5. Group reflex
When an object is brought close to limbs, animals grasp object and limb are extended.

grasping reflex, baby hand

6. Vestibular placing reaction
When blindfolded animal is brought down from height rapidly, forearm of animal extend and toes spread which assist animal to steadily land on ground.

Reflexes integrated in cerebral cortex

1. Optical righting reflex

  • Stimulus: Visual clues
  • Response: Righting of head

2. Hopping reactions
If a standing animal is pushed laterally, it hops (jumps) to maintain equilibrium.

3. Placing reaction

  • Stimulus: Visual, exteroceptive and proprioceptive receptors
  • Response: Foot placed on supporting surface in position to support body

Tags: brain stem, cortical reflex, grasping reflex, medullary reflexes, postural reflex, reflexes

Last updated: July 11, 2010

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This entry was posted by on July 11, 2010 at 8:10 pm and filed under Physiology category.

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