The five senses biology lesson for kids: 1st, 2nd, 3rd, 4th, 5th, 6th and 7th grades biology lesson.
Every living thing needs to have some way to know what’s happening in the world around it. In humans, the special organs pick up stimuli and send it to the different parts of the brain for processing, so that we can understand what we are detecting. We understand the world with five senses: sight, hearing, smell, taste, and touch.
In sight, the eyes pick up light that either comes from things like lightbulbs and fire, or bounces off objects. The light enters the eye through a hole in the front called the pupil, which is in the center of a colored disk called the iris. The light then passes through a transparent flexible tissue called the lens, which focuses the light on the back of the eye, called the retina. The retina has nerves, which, which stimulated, send signals to the brain for processing, so we can make sense of whatever object we see around us.
Hearing works in a different way, though. Instead of light, our ears pick up sound. The pinna, part of the ear that we can see, funnels sound into the ear canal, where it hits into a membrane called the ear drum. Here is where the outer ear stops, and the middle ear begins. Ear drum, the sound moves along the smallest bones in the body, carrying it to the inner ear, where there are nerve cells. The inner ear is filled with liquid that push and pull the nerves. The nerves then send signals to the brain, where these signals are processed, and we register speech, cars honking, or whatever sound it is that we heart.
Smell starts at the nose. As we breathe in, chemicals in the air brush against hairs at the top of the nasal cavity. These chemicals bind to receptors on the hairs, and that send signals to groups of nerve cells olfactory bulbs. These bulbs then send signals to the brain so we know is something smells sweet, delicious, or if it stinks.
The second to last sense we will discuss is taste, which starts on the tongue. The tongue has lots of little bumps called papillae (singular: papilla). When we eat, chemicals from the food move to the base of the papillae, where there are bundles of nerve cells called taste buds. These taste buds send signals along nerves to the brain, which then is able to process whether your food tastes good, or even if it’s spoiled and gross!
And then there’s touch. The skin, the largest organ in the entire human body, covers almost every surface, and is filled with nerve cells. In a way, touch is not just one single sense; different kinds of nerve cells pick up vibration, pressure, pain, etc., and send those signals to the brain for processing.
All these five senses work together to help us make sense of the world.