Question

Identify the labels.

• A. (A) Receptor (B) Sensory nerve fiber (C) Part of CNS (D) Afferent nerve fiber (E) Effector organ
• B. (A) Sensory nerve fiber (B) Afferent nerve fiber (C) Part of CNS (D) Efferent nerve fiber (E) Effector organ
• C. (A) Receptor (B) Afferent nerve fiber (C) Part of CNS (D) Motor nerve fiber (E) Effector organ
• D. (A) Receptor (B) Efferent nerve fiber (C) Part of PNS (D) Motor nerve fiber (E) Effector organ

Answer 1

The correct option is C (A) Receptor (B) Afferent nerve fiber (C) Part of CNS (D) Motor nerve fiber (E) Effector organ

Reflex arc is the pathway taken by nerve impulse generated at the receptor by a stimulus to reach the effector organ during a reflex action. It includes both sensory and motor nerves.
Reflex arc consists of:
A. Receptor - It is a tissue,cell or organ which receives an external or internal stimulus such as skin, eye, ear, etc. It sets up the sensory impulse.
B. Afferent or sensory nerve fibres - The impulse generated by the receptor is taken by sensory or afferent nerve fibres to the central nervous system through dorsal or posterior root of the spinal nerve.
C. Part of the central nervous system - It can be spinal cord, ganglion or brain. The sensory impulse is transferred here to the motor nerve fibers either through the relay neuron. The relay neurons are present in the spinal cord and it connects the sensory and motor neurons
D. Motor or efferent nerve fibers - These fibers carry the motor impulses generated in the central nervous system to specific effectors. In the spinal cord, the motor nerve fibres come out through the ventral or anterior root.
E. Effector organ - It may be an organ, gland or muscle which on being activated by motor impulse produces an effect or response to suitably deal with the stimulus.