Question

With the help of a neat and labelled diagram, describe reflex arc.

Sketch and label reflex arc

Answer 1

Reflex arc: The pathway of nerve fibers along which the reflex impulse travels is known as a reflex arc. It is always unidirectional from receptor organs to the effector organ, CNS. The reflex arc is the structural and functional unit of reflex action.

Components of simple reflex arc:
The simple reflex arc is formed of five components as given below:

1. Receptor organ:
It is a specialized part of the body called the sense organ that receives the stimulus and converts it into an impulse. e.g. skin, eye, tongue, nose, and ears.

2. Sensory or Afferent neuron:
It carries sensory nerve impulses from the receptor organ to CNS. Its cyton is located in the dorsal root ganglion. Its dendron is long and connected to a receptor, while the axon enters the grey matter of the spinal cord to form a synapse.

3. Associated or Intermediate neuron:
It is present in the grey matter of the spinal cord. It receives a sensory impulse, interprets it, and generates motor impulses. 

4. Motor or effector neuron:
Its cyton is present in the ventral horn of grey matter and the axon travels through the ventral root. It conducts motor impulses from the spinal cord to the effector organ.

5. Effector organ:
It is a specialized part of the body that is excited by receiving the motor impulse. It gives a proper response to the stimulus. e.g. Muscles and glands.