Reflexes and Descending Control of Reflexes

Question 1

Tonic Neck Reflexes

Answer 1

Position of limbs is determined by position of head
- head tilted down, forelimbs flex, hindlimb extend
- Head tilted up, forelimbs extend, hindlimbs flex.
- fencers pose

Question 2

Spinal Shock

Answer 2

Complete absence of reflexes after spinal transection.
- Reflexes gradually return

Question 3

Babinski sign

Answer 3

Damage to motor cortex or pyramidal tract
- Normal toes down
- B sign - fanning of toes.
(normal in 1-2 year olds)

Question 4

Abnormal Muscle tone (control of stretch reflex)

Answer 4

• Too Low (flaccidity) too little excitation - Down syndrome
• Too high (rigidity) too much excitation - Cerebral Palsy

Question 5

Rigidity - decerebrate

Answer 5

intercollicular transection of midbrain : increased tone in extensors all 4 limbs
- cut the dorsal roots, rigidity goes away

Question 6

Decorticate rigidity

Answer 6

• lesions of motor cortex (as seen from a stroke), effects seen on contralateral side of body.
• Different Pattern - increased tone in flexors of arms and extensors of legs on the contralateral side.

Question 7

Spasticity : Increased muscle tone (rigidity)

Answer 7

Clonus: more than one contraction for a single stretch.

Question 8

Contractures (danger)

Answer 8

shortening of tendons so that limb becomes immobile : can lead to joint problems like arthritis

Question 9

Treatments of Spasticity in CP

Answer 9

Dorsal Rhizotomy (cut afferents to stretch reflex), selected dorsal roots.
- Injections of baclofen (inhibitory transmitter) into spinal cord(implanted pump), inhibit the stretch reflex.

Question 10

Spasticity also seen Parkinson’s disease

Answer 10

BUT AFFECTS BOTH FLEXORS AND EXTENSORS, DIFFERENT PATTERN.