Neurophysiology Short Notes: Reflex Action, Spinocerebellar Tracts, And Nerve Conduction

Neurophysiology Short Notes: Reflex Action, Spinocerebellar Tracts, And Nerve Conduction

Question 1. Define reflex action and describe Babinski sign

Answer:

Reflex action:

• It is the response to a peripheral nervous stimulation that occurs without our consciousness.

Babinski’s sign:

• It is an abnormal plantar reflex
• It is elicited by a gentle scratch over the outer edge of the sole of the foot
• In normal plantar reflex it causes flexion and adduction of all toes
• In Babinski’s sign there is dorsiflexion of great toe and fanning of other toes
• It is present in
  • Upper motor neuron lesion
  • Infancy
  • Deep sleep

Question 2. Give the origin and termination of spinocerebellar tracts. Add a note on its functions.
Answer:

Question 3. What is saltatory conduction? Describe the classification of nerve fibres according to the rate of nerve conduction.
Answer:

Saltatory conduction:

1. Myelin sheath is impermeable to ions
2. Thus, sodium enter into nerve fibres from ECF only in the node of Ranvier and depolarisation occurs
3. Depolarisation occurs in successive nodes and action potential thus, jumps from one node to another node
4. This jumping is called saltatory conduction.

Classification of nerve fibres depending upon rate of conduction:

• Type A nerve fibres
  • Type A alpha- conduction velocity is 70-120 m/sec
  • Type A beta-conduction velocity is 30-40 m/sec
  • Type A gamma – conduction velocity is 15-30 m/sec
  • Type A delta – conduction velocity is 12-30 m/sec
  • Type B nerve fibres – conduction velocity is 3-20 m/sec
  • Type C nerve fibres
    1. Subtype 1-conduction velocity is 0.5-2 m/sec
    2. Subtype 2-conduction velocity is 0.7-2.3 m/sec