AP BIOLOGY

Detailed explanation-1: -Whenever we smell something, our nose and brain work together to make sense of hundreds of very tiny invisible particles, known as molecules or chemicals, that are floating in the air. If we sniff, more of these molecules can reach the roof of our nostrils and it is easier to smell a smell.

Detailed explanation-2: -When you smell a smelly substance, odorant molecules travel to your nose, where they bind to olfactory receptor cells (6), which generate electrical signals that are sent to a part of your brain called the olfactory bulb (1). Also shown are (2) mitral cells, (3) bone; (4) olfactory epithelium, and (5) glomerulus.

Detailed explanation-3: -Smells travel through the air by a process called diffusion; air particles, and the odour particles within the air, move freely in all directions. They are constantly moving and eventually they spread out through the air around them.

Detailed explanation-4: -Past studies have shown that airborne molecules linked to scents trigger receptor cells lining the nose to send electric signals to nerve-ending bundles in the bulb called glomeruli, and then to brain cells (neurons).

Detailed explanation-5: -The molecules we perceive as smells are called odorants. Odorant molecules stimulate sensory nerve cells (neurons) at the top of the nasal cavity and these respond by sending impulses to the brain (section 1.1).