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
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
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
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
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
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
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
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 :
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 ).
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