The central nervous system (2) is a combination of the brain (1) and the spinal cord (3). The central nervous system is coated with three layers of protective membranes called brains (from the Greek word membrane).

Coffee helps us stay awake as it binds to receptors for adenosine in our brain. Instead of slowing down because of the adenosine’s effect, the nerve cells speed up.

Surgical mask sare worn by doctors and dentists to help protect other people and the environment from the mask-wearer by trapping respiratory droplets. In case of COVID 19 the purpose of such masks, according to CDC, is to be used from those who are already ill to avoid spreading the virus around. Surgical masks are not the same as N95 respirators. N95 respirators are special tightly fitting masks that filter out viruses and bacteria. Health workers use N95 respirators at risk of inhaling infectious and other harmful particles, need to be professionally fitted and are not recommended by the CDC for members of the public.

The purpose of the retina is to get the light that the lens focuses on to convert light into neuronal signals and send these signals to the brain for visual recognition.