Reflex Actions

Reflex Action in Humans

Imagine;

• You withdraw your hand reflexively or immediately when you touch a hot surface.
• Your mouth starts watering as soon as you smell your favorite food.
• You move away as soon as you see a car coming close to you.

• In all the situations listed above, we respond to environmental changes or stimuli with an immediate or quick action or response .
  We do not think in such situations and our actions do not feel like they are      under our control .This is called a reflex action .

So, how are these reflex actions controlled and coordinated?

Consider touching a hot pan,

• If the signals are passed as nerve impulses like we had discussed in the previous section, we need to comprehend details like the possibility of getting hurt or getting burnt etc. before we move our hand. 
• But this pathway of transmitting messages is a complex process involving interaction between many neurons.
• We also need to consider the relatively long duration of this process.

So our body needs to opt for a mechanism that instructs us to immediately act upon the stimulus.

This is when Reflex Arc comes into picture.

• The reflex arc should have connections where the sensory neurons meet the motor neurons for the first time in the nervous system.
• Nerves from all over the body meet in a bundle at the spinal cord on their way to their brain .

The Reflex Arc

• The stimuli is sensed by the sensory receptors and sensory neurons generate impulses.
• These impulses reach the spinal cord.
•  

• Spinal cord in a bundle is a bundle of nerves.

• The relay neuron in the spinal cord passes signals between neurons.
• The motor neurons pass the signals for response to the organ that needs to respond to stimulus.

• Reflex arcs are formed in this spinal cord.
• The information input also goes on to reach the brain .
• Though we have complex neuron networks, reflex arcs are to be more efficient for quick responses.