Crossed extention reflex

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IRIN

1. crossed extension
reflex
IRIN ROLLY

2. WELCOME

3. INTRODUCTION
The crossed extension reflex or crossed extensor
reflex or crossed extensor response is a reflex in
which the contralateral limb compensates for loss of
support when the ipsilateral limb withdraws from
painful stimulus in a withdrawal reflex

4. SIR CHARLES SCOTT
SHERRINGTON
●Flexor and crossed extension reflex
was described by sir charles
sherrington in 1900s
Sir Charles Scott Sherrington OM PRS FRCP FRCS (27
November 1857 – 4 March 1952) was an English
neurophysiologist, histologist, bacteriologist, and a
pathologist, He received the Nobel Prize in Physiology
or Medicine with Edgar Adrian, 1st Baron Adrian, in
1932 for their work on the functions of neurons. )

6. Crossed extension reflex

● Occurs simultaneously, coordinated with flexor reflex
● crossed extensor reflex straits others legs
● to receive body weight
● maintained by reverberating circuits
eg; flexor reflex causes leg to pull up
An example of this is when a person steps on e nail: The leg that is stepping on the nail pulls
away, while the other leg takes the weight of the whole body.

7. What is withdrawal reflex ??

10. a reflexive action by a
contralateral limb to
compensate for loss of
support when the ipsilateral
limb withdraws from a
painful stimulus. The reflex,
which helps shift the burden
of body weight, is also
associated with the
coordination of legs in
walking by flexing muscles
on the left side when those
on the right are extending,
and vice versa.

11. Crossed extension reflex
● It is a reflex in which the contralateral (opposite side of the body) limb
compensates for loss of support when the ipsilateral (same side of the body)
limb withdraws from painful stimulus in a withdrawal reflex. During a
withdrawal reflex, the flexors in the withdrawing limb contract and the
extensors relax, while in the other limb, the opposite occurs as part of the
crossed extensor reflex
● Besides shifting the body weight to the other side, the reflex pathway is also
associated with leg coordination when walking by flexing muscle on one side,
●while extending muscle on the other side. This crossed extensor response is
properly part of the withdrawal reflex.

12. ●crossed extensor reflex is contralateral, meaning the reflex occurs on the The
opposite side of the body from the stimulus.
●
●To produce this reflex, branches of the afferent nerve fibers cross from the
stimulated side of the body to the contralateral side of the spinal cord. There,
they synapse with interneurons, which. in turn, excite or inhibit alpha motor
neurons to the muscles of the contralateral limb. In the ipsilateral leg (the one
which steps on the nail), the flexors contract and the extensors relax to lift the
leg from the ground. On the contralateral side (the one that bears all the
weight), the flexors relax and the extensors contract to stiffen the leg since it
must suddenly support the entire weight of the body.
●
●At the same time, signals travel up the spinal cord and cause contraction of the
contralateral muscles of the hip and abdomen to shift the body's centre of
gravity over the extended leg. To a large extent, the coordination of all these
muscles and maintenance of equilibrium is mediated by the cerebellum and
cerebral cortex.




CONT……...

13. Crossed extension reflex
✓ Not a separate reflex , but its accessory to, or part of , the
flexor reflex
➢ Synonyme- none
➢ Stimulus,receptors,,number of synapses same as flexor
reflex
➢ Purpose - contraction of extensor muscle of contralateral
limb to support weight
➢ After discharge - contraction outcast stimulus

14. crossed extension reflex (foot
reflex)

This is a primitive reflex that is
usually is only present until one
month of age. The examiner holds
one of the baby's legs extended and
applies firm pressure to the sole of
the foot of the same leg. The baby's
free leg flexes, adducts and then
extends. The adduction component
of the reflex is generally only
present after 36 weeks gestation.

16. . Flexion of a body part is often balanced by extension of the same body part
on the opposite side of the body

20. It is concluded that this sign, not formerly described, is a
pathological reflex or synkinesis(unwanted contraction of
muscles). In the cooperative patient the crossed extensor
response is a more sensitive indicator of a minor disturbance
within the corticospinal motor pathways than the Babinski
sign………….