Reflex arc is a neural pathway that controls reflex actions in the body. It involves a series of interconnected neurons that transmit sensory information from the peripheral nervous system to the central nervous system and then back to the effector organs, resulting in an involuntary response. The reflex arc serves as a rapid and automatic mechanism for the body to respond to stimuli without conscious thought. There are several key functions described in the reflex arc:

1. Sensory Receptor:
- The sensory receptor is the starting point of the reflex arc.
- It detects the stimulus from the external environment or within the body.
- Examples of sensory receptors include photoreceptors in the eyes, thermoreceptors in the skin, and stretch receptors in muscles.

2. Sensory Neuron:
- The sensory neuron carries the sensory information from the receptor to the spinal cord or brain.
- It is a specialized cell that converts the sensory stimulus into electrical signals, known as action potentials.
- The sensory neuron has a long dendrite to receive the signals and a single axon to transmit them.

3. Interneuron:
- The interneuron is located in the spinal cord or brain and serves as a link between the sensory and motor neurons.
- It processes and integrates the sensory information received from the sensory neuron.
- The interneuron determines the appropriate response and sends signals to the motor neuron.

4. Motor Neuron:
- The motor neuron receives signals from the interneuron and transmits them to the effector organ.
- It carries the instructions for the desired response.
- The motor neuron has a long axon to transmit the signals and branches at the end to connect with multiple effector cells.

5. Effector Organ:
- The effector organ is the target of the reflex action.
- It can be a muscle or gland that carries out the response.
- For example, if you accidentally touch a hot surface, the effector organ (your muscles) will quickly withdraw your hand to prevent further injury.

Overall, the reflex arc functions to provide quick and automatic responses to stimuli, helping to protect the body from potential harm. It bypasses conscious thought and allows for rapid actions to occur without delay.