Question

The diagram shows the structures involved in a reflex action. What shows the sequence in which these structures become involved?

• A. P $\to$ Q $\to$ R $\to$ S
• B. P $\to$ S $\to$ R $\to$ Q
• C. Q $\to$ R $\to$ S $\to$ P
• D. Q $\to$ S $\to$ P $\to$ R

Answer 1

The correct option is C Q $\to$ R $\to$ S $\to$ P

Receptor of the heat would be the heat sensor in the skin (Q), when it is stimulated the heat sensor generates an impulse which travels to relay neurone (S) along a sensory neurone (R) crossing synapse one. The relay neurone passes the impulse across a second synapse to a motor neurone (P) which in turn transmits the impulse to a muscle in the arm.