Question

What is a reflex action? Describe the steps involved in reflex action.

Answer 1

A reflex action is a type of animal behaviour which is responsible for involuntary and sudden response to a stimulus in case of a dangerous situation. The spinal cord plays a major role in the reflex arc.

Complete answer:
A reflex action is an involuntary, sudden and instantaneous movement in response to a stimulus against a dangerous situation. Example- Sudden jerky withdrawal of hand on contact with a hot pan. A reflex occurs due to the activity of neural pathways called reflex arcs which act upon an impulse before the impulse reaches the brain. Reflex arc may be defined as the path taken by the nerve impulses in a reflex. There are two types of reflexes: natural reflexes and conditioned reflexes.

A reflex action involves following steps:
Stimulus $\rightarrow$ Receptor organ $\rightarrow$ Afferent nerve fibre $\rightarrow$ Central Nervous system (spinal cord) $\rightarrow$ Efferent nerve fibre $\rightarrow$ Effector organ $\rightarrow$ Response.

Additional information:
- Nerves from various parts of the body bundle up in the spinal cord before they enter the brain. Reflex arcs are formed in the spinal cord. The components of the reflex arc are:

- Receptor organ: These are mainly the sense organs that senses the danger.
- Sensory/Afferent neurons: They pick up the signals from the sensory organ and transport the impulse through interconnected networks of neurons.
- Central nervous system: The spinal cord sends the necessary signal (such as withdrawal of hand etc) to the affected muscle through the motor neuron.
- Receptor/Afferent neuron: Carries the response from the spinal cord to the affected muscle.
- Response: This leads to the withdrawal of the muscle or the organ away from the danger.

Note: Reflexes can be either natural in which no previous experience or learning is required or it can be conditioned which develops during lifetime due to a particular experience or learning.