VPB 121: Veterinary Physiology - II (2+1)

Spinal animal

SPINAL ANIMAL (FROG)

• Spinal animal is prepared either transecting at the spinomedullary junction or by ligating both carotid arteries and the mid-vertebral artery to arrest the brain activities.
• Frog's head behind the tympanic membrane is transected to separate spinal cord from the brain. Transection is to be done below the foramen magnum.
• In these preparation when frog is palced on its back there is no spontaneous movement due to complete paralysis of the movement.
• When a portion of a skin is pricked with the needle no withdrawal reflex is noticed.
• This is known as “Spinal shock depression of the spinal function and is reversible.
• Spinal shock is removed in few minutes in a frog and few hours in a dog.
• Regaining from the spinal shock certain reflex activity are seen.
• When one of the limb is pulled down it is quickly drawn up.
• Withdrawal of the limb is noticed on pinching. (flexor reflex)
• If one of the limb is stimulated with the greater force all the limbs are flexed.
• However, respiratory movement voluntary movement righting reflexes are absent (they can’t swim when they place in the water).
• Except basic stretch reflex and supporting reactions all the other reflexes are absent.

Thalamic animal

• Cerebral cortex, white matter some portion of the basal ganglia are removed.
• Thalamus and hypothalamus with the caudal portion of the basal ganglia remain intact.
• These animals show righting reflexes and temperature regulation.
• Reflexes associated with emotional states fight and anger are present .
• Tonic labyrinth and tonic neck reflexes and other righting reflexes are present.
• Propriokinesthetic, righting reflexes placing reactions and hopping reflexes are absent.