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Dr Raghuveer Choudhary
Postural reflexes Physiology
Postural reflexes Physiology
POSTURE & ITS
REGULATION:
 POSTURE: A state of equilibrium in
the space or position adopted by an
individual in the environment.
POSTURE
Posture
Balance
MECHANISMS OF POSTURE
Two mechanisms
Muscle tone
2. Postural reflexes.
posture reflex
adjustments of tone in the antigravity muscles.
human flexors of upper extremity &
extensors of lower extremity antigravity
basic postural reflex
stretch reflex.
 centre of gravity of head the centre
of gravity of atlanto-occipital joint
 cervico-occipital
muscles

stretching quadriceps muscles

• This ensures that the knee joints the main weight
bearing joints do not give way under the effect of
gravity.
• This maintains the leg as a pillar of support & thus
counteracts the gravitational displacement of the
body.
• Various postural reflexes influence the medial motor
systems & the motor neurons of antigravity muscles.

excite both alpha
& gamma motor neurons that innervate antigravity
muscles & their spindles.

1. Lateral vestibulospinal tract
2. Pontine reticulospinal tract.
 It is a spinal
reflex with supraspinal control.
 The centre for muscle tone lies in anterior motor neurons( α- motor
neurons) of spinal cord, which are stimulated through a constant γ-
motor neuron discharge.
 pyramidal &
extrapyramidal fibres
• Bulboreticular facilitatory area pons
facilitatory gamma
motor neurons
• Bulboreticular inhibitory area medulla
cerebellum or cerebral cortex inhibits gamma
motor discharge.
stretch reflexes
facilitatory
inhibitory
• These effects are exerted via
Gamma efferents
• It directly stimulate Alpha
motor neurons
• Increased tone produced by it
is called Alpha rigidity
Motor cotex
Basal
ganglia
cerebellum
Inhibitory
reticular
formation
Facilitatory reticular
formation
Vestibular
nucleus
POSTURAL REFLEXES
maintain the body in upright & balanced
position
• Provide adjustments
REFLEX ARC OF POSTURAL REFLEXES
• Afferent pathways
• Integrating center
• Efferent pathways
TYPES OF POSTURAL REFLEXES
Static reflexes:
elicited by gravitational pull
Maintain
Statokinetic reflexes
• Elicited displacement
• Maintain
TYPES OF POSTURAL REFLEXES
• Static reflexes
TYPES OF POSTURAL REFLEXES
LOCAL STATIC REFLEXES -
same limb
REFLEX STIMULUS RESPONSE RECEPTORS INTEGRATING
CENTRE IN CNS
A.Static
reflexes
1.Local static
reflexes
Stretch reflex
2.Positive
Supporting
reflex
3.Negative
supporting
reaction
Stretch
Contact of skin
of the sole of
foot with ground
Stretch of
extensor
muscles
Contraction of
antigravity
muscles
Contraction of
flexors and
extensors of
the limb.
Disappearance
of positive
supporting
reaction
Muscles
spindles
Touch and
pressure
receptors from
skin of sole of
foot.
Proprioceptors
in extensors
Spinal cord and
mid brain
Spinal cord
Spinal cord
VARIOUS POSTURAL REFLEXES
Postural reflexes Physiology
TYPES OF POSTURAL REFLEXES
1. Reflex control of antigravity muscle tone:
TYPES OF POSTURAL REFLEXES
2. Positive supporting reaction:
both extensors & flexors
• Plays imp role
• Afferent impulses
TYPES OF POSTURAL REFLEXES
TYPES OF POSTURAL REFLEXES
3. Negative supporting reaction:
TYPES OF POSTURAL REFLEXES
SEGMENTAL STATIC REFLXES -
bilateral reflex
• Example
Role
REFLEX STIMULUS RESPONSE RECEPTORS INTEGRATING
CENTRE IN CNS
2.Segmental
static reflexes
Crossed
extensor reflex
3.General static
reflexes
Attitudinal
reflexes
1. Tonic
labyrinthine
reflex
2. Tonic neck
reflex
Painful
stimulus
Gravity
(alternation of
position of head
relative to
horizontal plan)
Stretch of neck
muscles due to
alternation of
position of head
relative to body.
Contraction of
flexors of the
ipsilateral limb and
extensors of
contralateral limb
to support the
body.
Extensor rigidity
Flexion of forelimbs
and extension of hind
limbs on ventroflexion
of head .extension of
fore limbs and flexion
of hindlimbs.flexion of
ipsilateral limbs and
extension of
contralateral limbs on
turning the head side-
ways.
Nociceptors
Otolith organs
Pacinian
corpuscles in
the ligaments
of cervical joint
and muscles
spindles of
neck muscles.
Spinal cord
Vestibular and
reticular nuclei
present in the
medulla
oblongata.
Medulla
Postural reflexes Physiology
Postural reflexes Physiology
TYPES OF POSTURAL REFLEXES
GENERAL STATIC REFLXES -
generalized reflex response
TYPES OF POSTURAL REFLEXES
Attitudinal Reflexes -
Postural reflexes Physiology
TYPES OF POSTURAL REFLEXES
Tonic Labyrinthine Reflex -
position of head
relative to horizontal plane
• Stimulus:
• Receptors :
• Afferents:
• Center:
• Efferents:
TYPES OF POSTURAL REFLEXES
• Reflex response:
Postural reflexes Physiology
Postural reflexes Physiology
TYPES OF POSTURAL REFLEXES
Tonic Neck Reflex -
position of head
relative to body
• Stimulus:
• Receptors:
• Center:
• Efferent:
TYPES OF POSTURAL REFLEXESRESPONSE
• Reflex response:
Postural reflexes Physiology
Postural reflexes Physiology
Tonic Neck Reflex
• Medulla Reflexes
• Tonic neck reflex (primitive reflex found in newborn)
• head up causes
• hind limbs to flex
• fore limbs to extend
• head down
• fore limbs flex
• hind limbs extend
• head turn to one side
• limbs on the side where head is turned to
extend/straighten
• opposite side is bent/flexed
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
REFLEX RESPONSE
IMPORTANCE
, tonic labyrinthine reflex
TYPES OF POSTURAL REFLEXES
LONG LOOP STRETCH REFLEXES [Righting Reflexes]
RIGHTING REFLEXES
Postural reflexes Physiology
RIGHTING REFLEX
1. HEAD RIGHTING REFLEX
• Labyrinthine righting reflex
head is in lateral position
saccules
Postural reflexes Physiology
• neck righting reflex
• Stimulus: stretch of neck muscles
• Response: righting of thorax and shoulders
• receptors: muscle spindles
• eg.A newborn's reflex to turn his trunk and shoulders to the
same side his head is turned
1. HEAD RIGHTING REFLEX
2. BODY RIGHTING [BODY-ON-HEAD] REFLEX
• Body-on-head righting reflex
differential stimulation
2. BODY RIGHTING REFLEX
3. NECK RIGHTING [NECK-ON-BODY] REFLEX
• Also called Neck–on-Body
head is righted but the body remains in
lateral position twisting of neck
thorax & lumbar region successively into upright
position
4. BODY-ON-BODY RIGHTING REFLEX
body is lying
• Righting of head is prevented
righting the body
directly
5. OPTICAL RIGHTING REFLEX
• Optical impulses
even after denervation of the
labyrinths & neck muscles
CENTERS OF RIGHTING REFLEX
Center for all righting reflexes
Center for optical righting reflex-
REFLEX STIMULUS RESPONSE RECEPTORS INTEGRATING
CENTRE IN CNS
2.Long loop stretch
reflex
3.Righting reflexes
• Labyrinthine
righting reflex
•Body righting
reflex
•Neck righting
reflex
•Body on body
righting reflex
•Limbs righting
reflex
• optical
righting reflex
Stretch of the
muscle due to
swaying of body
Gravity
Pressure on side of
body
Stretch of neck
muscles
Pressure on side of
the body
Stretch of limb
muscles
Visual cues
Continuous
moment to
moment
corrections of
sways which occurs
during standing.
Brings the head in
upright level
Righting of head.
Righting of thorax
and shoulders and
then pelvis
Righting of body
even when righting
of head is
prevented.
Appropriate
posture of limbs
Righting of head
Muscle
spindles(monosyna
ptic reflex) visual
receptor(long loon
reflex)
Otolith organs in
saccules of
labyrinth.exterocep
tors
Exteroceptors
Muscle spindles
Exteroceptors
Muscle spindles
Eyes
Spinal cord
Cerebral cortex
Mid brain
Mid brain
Mid brain
Mid brain
Mid brain
Cerebral cortex
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
STATO-KINETIC REFLEXES
• Elicited by angular linear acceleratory
stimuli
REFLEX STIMULUS RESPONSE RECEPTORS INTEGRATING
CENTRE IN CNS
B.Statokinetic
reflexes
•Vestibular
placing reaction
•Visual placing
reaction
•Hopping
reactions
Linear
acceleration
Visual cues
Lateral
displacement
while standing
Foot placed on
supporting surface
in position to
support body.
Foot places on
supporting surface.
Hops, maintains
the limb in position
to support the body
Receptors in
utricle and
saccule .
Eyes
Muscle spindle
Cerebral cortex
Cerebral cortex
Cerebral cortex
Postural reflexes Physiology
1. VESTIBULAR PLACING REACTION
linear acceleration
prepares the animal for appropriate
support by the limbs on surface contact
VESTIBULAR PLACING REACTION
VISUAL PLACING REACTION
HOPPING REACTION
hopping movements that keep the limbs in
position to support the body
lateral displacement
Optical righting reflex :
Visual stimuli that enable an
animal to maintain the correct
position of the head in space,
by bringing about movements
of the muscles of the neck
and limbs.
visual clues –> righting of
the head
Placing reflex : when the
infant is held erect and the
dorsum of the foot is drawn
along the under edge of a
table top  flexion followed
by extension of the leg
Appears by 4 days in the
newborn
Stepping Reflex
When feet touch the ground
, the infant appears to take
some steps
Stepping reflex disappears
before walking :
Hopping reaction
Postural reflexes Physiology
• Postural Control Centers :
• Cerebral cortex
• Optical Righting reflex
• Placing Reaction
• Hopping Reaction
• Midbrain : the Midbrain Righting
Reflexes 
• (a) Labyrinthine
• (b) Neck
• (c) Body on Head
• (d) Body on Body
• Medulla
• (1) Tonic Labyrinthine Reflex
• (2) Tonic Neck Reflex
• Spinal Cord
• Positive and Negative Supporting
Reaction
• Stretch Reflex
Postural reflexes Physiology
Postural reflexes Physiology
transection of spinal cord at
lower cervical level
•decerebrate rigidity
midbrain
pons
medulla
decerebrate rigidity
• tonic reflexes are seen
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Site of lesion  between the
superior and inferior colliculi of
the midbrain , lesion below Red
Nucleus , resulting in
extensive extensor posture of all
extremeties  Rigidity of all 4
limbs
 All limbs extended
 (hallmark  elbows extended)
Head may be arched to the back
It is due to 
(1) increased general excitability
of the motor neuron pool 
especiallly Gamma efferent
discharge ( due to facilitatory
effects of the un inhibited
Vestibulospinal Tract ) .
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
• Decerebrate rigidity is not commonly found in man.
• The pattern in true rigidity is extensor in all 4 limbs.
• The actual decerebrate rigidity generally shows extensor
rigidity in legs & moderate flexion in arms due to lesions
of cerebral cortex with most of brain stem intact.
• Decorticate animal is one in whom the whole cerebral cortex is removed but
the basal ganglia and brain stem are left intact
full extension of legs
arms lying across the chest
flexion of wrist and fingers
•decortication
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Decorticate posture
• Level of lesion lies above the Red
Nucleus.
• So the RubrospinalTract remain intact.
• It supplies flexor group of motor
neurons in upper limb
• So in decorticate rigidity where the
rubrospinal tract is intact the upper
limbs are flexed
Decerebrate posture
• In midcollicular section, the
rubrospinal tract is sectioned
• as thelevel of midcollicular section
passes below the Red Nucleus .
• So flexion of upper limb is absent
and all 4 limbs are extended
• In humans , where true
decerebrate rigidty is rare ,
since the damage to the
brain centers involved in it
are lethal.
• However decorticate
rigidity can be caused by
bleeding in the internal
capsule which causes UMNL
(damage to upper motor
neurons) .
• Symptoms & Signs :
• Flexion in the upper limbs
and extension in the lower
limbs.
• Arms flexed & bent inwards
towards chest
• Feet turned inward
• Seen in corticospinal animal :
damage above Red Nucleus
( in cerebral hemispheres ,
internal capsule or thalamus ).
Motor cotex
Basal
ganglia
cerebellum
Inhibitory
reticular
formation
Facilitatory reticular
formation
Vestibular
nucleus
Postural reflexes Physiology
•decortication
Decorticate
Animal Decerebrate
Spinal Animal
Levels of Lesions
Postural reflexes Physiology
postural adjustments
vestibular nuclei
cerebellum
pressure
& other
receptors
neck
receptors
Retina Occulomotor system
vestibular
system
complex pathways
• Animal Experiments show increased tone or rigidity.
• DifferentTypes
• 1 Decerebrate Rigidity-Sherrington and ischemic.
• 2 Decorticate Rigidity.
• 3 Lead Pipe Rigidity.
• 4 Cogwheel Rigidity.- 3 &4 are found in Parkinson’s Disease
Types of Rigidity
• 5 Decerebellate Rigidity-found in animals.In humans
cerebellectomy is associated with hypotonia.
• True rigidity is hypertonia in both extensor and flexor group of
muscles and is found in lead pipe and cogwheel rigidity of
Parkinsonism.
• All other types of rigidity mentioned above are really spaticity
where only one group of mucle show hypertonia
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology
Postural reflexes Physiology

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Postural reflexes Physiology

  • 4. POSTURE & ITS REGULATION:  POSTURE: A state of equilibrium in the space or position adopted by an individual in the environment.
  • 6. MECHANISMS OF POSTURE Two mechanisms Muscle tone 2. Postural reflexes.
  • 7. posture reflex adjustments of tone in the antigravity muscles. human flexors of upper extremity & extensors of lower extremity antigravity basic postural reflex stretch reflex.
  • 8.  centre of gravity of head the centre of gravity of atlanto-occipital joint  cervico-occipital muscles  stretching quadriceps muscles 
  • 9. • This ensures that the knee joints the main weight bearing joints do not give way under the effect of gravity. • This maintains the leg as a pillar of support & thus counteracts the gravitational displacement of the body. • Various postural reflexes influence the medial motor systems & the motor neurons of antigravity muscles.
  • 10.  excite both alpha & gamma motor neurons that innervate antigravity muscles & their spindles.  1. Lateral vestibulospinal tract 2. Pontine reticulospinal tract.
  • 11.  It is a spinal reflex with supraspinal control.  The centre for muscle tone lies in anterior motor neurons( α- motor neurons) of spinal cord, which are stimulated through a constant γ- motor neuron discharge.  pyramidal & extrapyramidal fibres
  • 12. • Bulboreticular facilitatory area pons facilitatory gamma motor neurons • Bulboreticular inhibitory area medulla cerebellum or cerebral cortex inhibits gamma motor discharge.
  • 14. facilitatory inhibitory • These effects are exerted via Gamma efferents • It directly stimulate Alpha motor neurons • Increased tone produced by it is called Alpha rigidity
  • 16. POSTURAL REFLEXES maintain the body in upright & balanced position • Provide adjustments
  • 17. REFLEX ARC OF POSTURAL REFLEXES • Afferent pathways • Integrating center • Efferent pathways
  • 18. TYPES OF POSTURAL REFLEXES Static reflexes: elicited by gravitational pull Maintain Statokinetic reflexes • Elicited displacement • Maintain
  • 19. TYPES OF POSTURAL REFLEXES • Static reflexes
  • 20. TYPES OF POSTURAL REFLEXES LOCAL STATIC REFLEXES - same limb
  • 21. REFLEX STIMULUS RESPONSE RECEPTORS INTEGRATING CENTRE IN CNS A.Static reflexes 1.Local static reflexes Stretch reflex 2.Positive Supporting reflex 3.Negative supporting reaction Stretch Contact of skin of the sole of foot with ground Stretch of extensor muscles Contraction of antigravity muscles Contraction of flexors and extensors of the limb. Disappearance of positive supporting reaction Muscles spindles Touch and pressure receptors from skin of sole of foot. Proprioceptors in extensors Spinal cord and mid brain Spinal cord Spinal cord VARIOUS POSTURAL REFLEXES
  • 23. TYPES OF POSTURAL REFLEXES 1. Reflex control of antigravity muscle tone:
  • 24. TYPES OF POSTURAL REFLEXES 2. Positive supporting reaction: both extensors & flexors • Plays imp role • Afferent impulses
  • 25. TYPES OF POSTURAL REFLEXES
  • 26. TYPES OF POSTURAL REFLEXES 3. Negative supporting reaction:
  • 27. TYPES OF POSTURAL REFLEXES SEGMENTAL STATIC REFLXES - bilateral reflex • Example Role
  • 28. REFLEX STIMULUS RESPONSE RECEPTORS INTEGRATING CENTRE IN CNS 2.Segmental static reflexes Crossed extensor reflex 3.General static reflexes Attitudinal reflexes 1. Tonic labyrinthine reflex 2. Tonic neck reflex Painful stimulus Gravity (alternation of position of head relative to horizontal plan) Stretch of neck muscles due to alternation of position of head relative to body. Contraction of flexors of the ipsilateral limb and extensors of contralateral limb to support the body. Extensor rigidity Flexion of forelimbs and extension of hind limbs on ventroflexion of head .extension of fore limbs and flexion of hindlimbs.flexion of ipsilateral limbs and extension of contralateral limbs on turning the head side- ways. Nociceptors Otolith organs Pacinian corpuscles in the ligaments of cervical joint and muscles spindles of neck muscles. Spinal cord Vestibular and reticular nuclei present in the medulla oblongata. Medulla
  • 31. TYPES OF POSTURAL REFLEXES GENERAL STATIC REFLXES - generalized reflex response
  • 32. TYPES OF POSTURAL REFLEXES Attitudinal Reflexes -
  • 34. TYPES OF POSTURAL REFLEXES Tonic Labyrinthine Reflex - position of head relative to horizontal plane • Stimulus: • Receptors : • Afferents: • Center: • Efferents:
  • 35. TYPES OF POSTURAL REFLEXES • Reflex response:
  • 38. TYPES OF POSTURAL REFLEXES Tonic Neck Reflex - position of head relative to body • Stimulus: • Receptors: • Center: • Efferent:
  • 39. TYPES OF POSTURAL REFLEXESRESPONSE • Reflex response:
  • 43. • Medulla Reflexes • Tonic neck reflex (primitive reflex found in newborn) • head up causes • hind limbs to flex • fore limbs to extend • head down • fore limbs flex • hind limbs extend • head turn to one side • limbs on the side where head is turned to extend/straighten • opposite side is bent/flexed
  • 50. TYPES OF POSTURAL REFLEXES LONG LOOP STRETCH REFLEXES [Righting Reflexes]
  • 54. 1. HEAD RIGHTING REFLEX • Labyrinthine righting reflex head is in lateral position saccules
  • 56. • neck righting reflex • Stimulus: stretch of neck muscles • Response: righting of thorax and shoulders • receptors: muscle spindles • eg.A newborn's reflex to turn his trunk and shoulders to the same side his head is turned
  • 58. 2. BODY RIGHTING [BODY-ON-HEAD] REFLEX • Body-on-head righting reflex differential stimulation
  • 60. 3. NECK RIGHTING [NECK-ON-BODY] REFLEX • Also called Neck–on-Body head is righted but the body remains in lateral position twisting of neck thorax & lumbar region successively into upright position
  • 61. 4. BODY-ON-BODY RIGHTING REFLEX body is lying • Righting of head is prevented righting the body directly
  • 62. 5. OPTICAL RIGHTING REFLEX • Optical impulses even after denervation of the labyrinths & neck muscles
  • 63. CENTERS OF RIGHTING REFLEX Center for all righting reflexes Center for optical righting reflex-
  • 64. REFLEX STIMULUS RESPONSE RECEPTORS INTEGRATING CENTRE IN CNS 2.Long loop stretch reflex 3.Righting reflexes • Labyrinthine righting reflex •Body righting reflex •Neck righting reflex •Body on body righting reflex •Limbs righting reflex • optical righting reflex Stretch of the muscle due to swaying of body Gravity Pressure on side of body Stretch of neck muscles Pressure on side of the body Stretch of limb muscles Visual cues Continuous moment to moment corrections of sways which occurs during standing. Brings the head in upright level Righting of head. Righting of thorax and shoulders and then pelvis Righting of body even when righting of head is prevented. Appropriate posture of limbs Righting of head Muscle spindles(monosyna ptic reflex) visual receptor(long loon reflex) Otolith organs in saccules of labyrinth.exterocep tors Exteroceptors Muscle spindles Exteroceptors Muscle spindles Eyes Spinal cord Cerebral cortex Mid brain Mid brain Mid brain Mid brain Mid brain Cerebral cortex
  • 68. STATO-KINETIC REFLEXES • Elicited by angular linear acceleratory stimuli
  • 69. REFLEX STIMULUS RESPONSE RECEPTORS INTEGRATING CENTRE IN CNS B.Statokinetic reflexes •Vestibular placing reaction •Visual placing reaction •Hopping reactions Linear acceleration Visual cues Lateral displacement while standing Foot placed on supporting surface in position to support body. Foot places on supporting surface. Hops, maintains the limb in position to support the body Receptors in utricle and saccule . Eyes Muscle spindle Cerebral cortex Cerebral cortex Cerebral cortex
  • 71. 1. VESTIBULAR PLACING REACTION linear acceleration prepares the animal for appropriate support by the limbs on surface contact
  • 74. HOPPING REACTION hopping movements that keep the limbs in position to support the body lateral displacement
  • 75. Optical righting reflex : Visual stimuli that enable an animal to maintain the correct position of the head in space, by bringing about movements of the muscles of the neck and limbs. visual clues –> righting of the head
  • 76. Placing reflex : when the infant is held erect and the dorsum of the foot is drawn along the under edge of a table top  flexion followed by extension of the leg Appears by 4 days in the newborn Stepping Reflex When feet touch the ground , the infant appears to take some steps Stepping reflex disappears before walking :
  • 79. • Postural Control Centers : • Cerebral cortex • Optical Righting reflex • Placing Reaction • Hopping Reaction • Midbrain : the Midbrain Righting Reflexes  • (a) Labyrinthine • (b) Neck • (c) Body on Head • (d) Body on Body • Medulla • (1) Tonic Labyrinthine Reflex • (2) Tonic Neck Reflex • Spinal Cord • Positive and Negative Supporting Reaction • Stretch Reflex
  • 82. transection of spinal cord at lower cervical level
  • 84. decerebrate rigidity • tonic reflexes are seen
  • 90. Site of lesion  between the superior and inferior colliculi of the midbrain , lesion below Red Nucleus , resulting in extensive extensor posture of all extremeties  Rigidity of all 4 limbs  All limbs extended  (hallmark  elbows extended) Head may be arched to the back It is due to  (1) increased general excitability of the motor neuron pool  especiallly Gamma efferent discharge ( due to facilitatory effects of the un inhibited Vestibulospinal Tract ) .
  • 100. • Decerebrate rigidity is not commonly found in man. • The pattern in true rigidity is extensor in all 4 limbs. • The actual decerebrate rigidity generally shows extensor rigidity in legs & moderate flexion in arms due to lesions of cerebral cortex with most of brain stem intact.
  • 101. • Decorticate animal is one in whom the whole cerebral cortex is removed but the basal ganglia and brain stem are left intact
  • 102. full extension of legs arms lying across the chest flexion of wrist and fingers
  • 107. Decorticate posture • Level of lesion lies above the Red Nucleus. • So the RubrospinalTract remain intact. • It supplies flexor group of motor neurons in upper limb • So in decorticate rigidity where the rubrospinal tract is intact the upper limbs are flexed Decerebrate posture • In midcollicular section, the rubrospinal tract is sectioned • as thelevel of midcollicular section passes below the Red Nucleus . • So flexion of upper limb is absent and all 4 limbs are extended
  • 108. • In humans , where true decerebrate rigidty is rare , since the damage to the brain centers involved in it are lethal. • However decorticate rigidity can be caused by bleeding in the internal capsule which causes UMNL (damage to upper motor neurons) . • Symptoms & Signs : • Flexion in the upper limbs and extension in the lower limbs. • Arms flexed & bent inwards towards chest • Feet turned inward • Seen in corticospinal animal : damage above Red Nucleus ( in cerebral hemispheres , internal capsule or thalamus ).
  • 114. postural adjustments vestibular nuclei cerebellum pressure & other receptors neck receptors Retina Occulomotor system vestibular system complex pathways
  • 115. • Animal Experiments show increased tone or rigidity. • DifferentTypes • 1 Decerebrate Rigidity-Sherrington and ischemic. • 2 Decorticate Rigidity. • 3 Lead Pipe Rigidity. • 4 Cogwheel Rigidity.- 3 &4 are found in Parkinson’s Disease
  • 116. Types of Rigidity • 5 Decerebellate Rigidity-found in animals.In humans cerebellectomy is associated with hypotonia. • True rigidity is hypertonia in both extensor and flexor group of muscles and is found in lead pipe and cogwheel rigidity of Parkinsonism. • All other types of rigidity mentioned above are really spaticity where only one group of mucle show hypertonia