Questions

The nervous system is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body.

In vertebrates it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body.

The nervous system has three main functions:

* To collect sensory input from the body and external environment.

* To process and interpret the sensory input.

* To respond appropriately to the sensory input.

The photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force. The photon has zero rest mass and always moves at the speed of light within a vacuum.

Tetrad is a homologous chromosome pair in the given options. A homologous chromosome pair is a pair of chromosomes one from father and one from mother that has same gene sequence after the process of meiosis.