Question

Draw and label the mechanism of the reflex arc.

Answer 1

Hint: A reflex action is the sudden involuntary response to a stimulus. It is the form of behaviour of human beings/vertebrates in which stimulation of sensory organs results in activity of some organ without will.

Complete answer: The reflex arc is a neural pathway which is responsible for the sudden reaction known as a reflex action. These reflex arcs are of two types
1) Autonomic reflex arcs: It is mediated by the spinal cord.
2) Somatic reflex arcs mediated by the brain.
Most of our body's reflex actions are controlled by the spinal cord and are known as a spinal reflex action, while some are controlled by the brain and those are known as the cerebral reflex action. The reflex of pain withdrawal is an automatic movement, in which the body responds to pain by seeking to step away from the pain source. Measures that are involved in a reflex arc includes:
a) Receptor - It is the sensory organ of the skin, muscle, or other organs. The sensory neuron brings momentum into the CNS.
b) Interneuron - It gives energy to the CNS.
c) Motor neuron - Here, the pulse is taken away from the CNS.
d) Effector - These are structures of the body such as the muscle, glands, etc.
The reaction is so swift that, if you walk with your right foot on a sharp edge, the pain withdrawal reflex would allow you to raise your right leg until the pain is felt by your brain. In the case of the knee, the effector’s muscles are flexors in the right leg that bend as they contract.

Note: When a reflex arc in an animal consists of only one sensory neuron and one motor neuron, it is defined as monosynaptic, referring to the presence of a single chemical synapse.