Question

What is the stimulus-response model of the nervous system?

Answer 1

Nervous system is the control system for all our actions, thinking and behaviour. It helps to coordinate with all the activities of our body. It also helps all other systems of our body to work together.
It is like a manager inside our body. The human nervous system receives the information from the surroundings, processes it, interprets it and then responds accordingly.

Complete answer: The units that make up the nervous system are called neurons or nerve cells. So, the neuron is the structural and functional unit of the nervous system. Neurons are of three types.

The changes in the environment to which the organisms respond or react are called stimuli (singular- stimulus). The living organisms show response or react to the stimuli such as light, heat, taste, sound, etc.
Stimulus-response model
Now, we look at an example to understand the model more clearly.
A reflex action is the action which we perform automatically. If we unknowingly touch a hot plate, we immediately move our hand away from it. This happens as follows:
The receptors which are present in our skin detect a stimulus. Like in the first example stimulus is change in temperature (heat).
Sensory neurons send the electrical impulses to a relay neuron which is located in a spinal cord of the central neuron system. Relay neurons connect sensory neurons to motor neurons.
Motor neurons then send electrical impulses to an effector (cell that acts in response to a stimulus).
Effectors produce a response. In the first example – muscles contract to move the hand away.

Note: A neuron made up of three components – cell body, dendrites and axon. The messages that are transmitted in the nervous system are in the form of electrical impulses called nerve impulses.
We can take other examples like moving our feet when we step on something sharp. The pupils get smaller in bright light, etc. in reflex action, we are unaware that anything is going to happen with us.