Solution:
∙ The automatic (involuntary) & rapid response to a stimulus that minimises any damage to the body from potentially harmful conditions, like touching something hot is called a reflex action.
∙ The following is the pathway of reflex arc:
A- Stimulus, B- Receptor, C- Sensory nerve, D- Motor nerve, E- Effector, F- Response
A: A stimulus gets generated due to hitting the knee with a hammer.
B: The receptor cells get stimulated.
C: This initiates an impulse in a sensory neuron that travels to the spinal cord. Here it passes, by means of a synapse, to a connecting neuron called the relay neuron situated in the spinal cord.
D: The relay neuron, in turn, makes a synapse with one or more motor neurons that transmit the impulse to the muscles.
E: The effector muscles (quadriceps muscle) initiate a response of jerking of the knee.
