Step I Decerebrate rigidity question?

[ihatescience]

From Costanzo's Physiology textbook:

"Both the pontine reticular formation and the lateral vestibular nucleus have powerful effects on extensor muscles. Therefore, lesions of the brain stem above the pontine reticular formation and lateral vestibular nucleus, but below the midbrain, cause a dramatic increase in extensor tone, called decerebrate rigidity. Lesions above the midbrain do not cause decerebrate rigidity."

Dumb question, but why would a lesion above the pontine reticular formation/lateral vestibular nucleus cause increased extensor tone (wouldn't they be 'inactivated' or something)?

Thanks a lot!

 

[perilou]

From Costanzo's Physiology textbook:

"Both the pontine reticular formation and the lateral vestibular nucleus have powerful effects on extensor muscles. Therefore, lesions of the brain stem above the pontine reticular formation and lateral vestibular nucleus, but below the midbrain, cause a dramatic increase in extensor tone, called decerebrate rigidity. Lesions above the midbrain do not cause decerebrate rigidity."

Dumb question, but why would a lesion above the pontine reticular formation/lateral vestibular nucleus cause increased extensor tone (wouldn't they be 'inactivated' or something)?

Thanks a lot!

They lose their inhibition. By default they are activated, and it is only upper neurons that inhibit them and result in us all not stiffening up.

 

[ihatescience]

They lose their inhibition. By default they are activated, and it is only upper neurons that inhibit them and result in us all not stiffening up.

Thank you!!