Class X Biology - Chapter: Control and Coordination - Topic: Reflex Arc Numerical Problems (Conceptual)

Problem 1: Time Taken for a Reflex Action (Conceptual)

If the nerve impulse travels at an average speed of 100 meters per second (m/s) and a reflex arc involves a total neural pathway length of 0.5 meters, how long (in milliseconds) would it take for the reflex action to occur?

Solution:

Time = Distance / Speed

Distance = 0.5 meters Speed = 100 meters/second

Time = 0.5 m / 100 m/s = 0.005 seconds

To convert seconds to milliseconds, multiply by 1000: Time in milliseconds = 0.005 s * 1000 ms/s = 5 milliseconds

Therefore, it would take approximately 5 milliseconds for the reflex action to occur.

Problem 2: Number of Synapses in a Polysynaptic Reflex (Conceptual)

A polysynaptic reflex involves an interneuron between the sensory neuron and the motor neuron. If a reflex arc has one sensory neuron, one interneuron, and one motor neuron, how many synapses are involved in this reflex pathway?

Solution:

• Synapse 1: Between the sensory neuron and the interneuron.
• Synapse 2: Between the interneuron and the motor neuron.

Therefore, there are 2 synapses involved in this polysynaptic reflex pathway.