The sense of hearing is actually due to a response to mechanical stimuli; vibrations are converted into nerve impulses that the brain receives.
- Humans can hear sounds up to 20 kHz. The greater wax moth can hear sounds up to 300 kHz!
- The cilia in the ear push earwax out of the ear naturally.
- Snakes hear from their jawbones! No, really. Their inner ears are connected to their jawbones, so vibrations travel from the jawbones to the ear before being processed.
- One of the earliest known forms of body modification is ear piercing.
- Hearing and touch are the only senses that are types of mechanosensation.
- The human ear is made of three sections. The middle ear contains the smallest bones in the body, known as the ossicles (hammer, anvil, and stirrup).
- Crickets hear using organs called tympanum on their front legs.
We see when visible light is processed by the eye’s components and translated into neural impulses that are processed by the brain.
- People blink 15 times per minute on average.
- Everything would appear two-dimensional to a person with only one eye.
- Human eyes are made of over two million working parts.
- Newborn babies see everything upside down until the brain learns to process everything right side up.
- Dolphins sleep with one eye open. Creepy? Or super smart?
The way the sense of touch works is complex. Simply put, a stimulus triggers activity in a sensory neuron, which then passes to the part of the brain that’s assigned to the proper body location.
- The sense of touch is the first to develop in humans at about 8 weeks into the gestation period.
- Touch stimulates the brain to release endorphins.
- Blood pressure and heart rate can be reduced by a touch.
- Whiskers are used by animals for tactile sensing for a number of survival purposes, including navigation, detecting water currents, and texture discrimination. Research is still ongoing to determine even more purposes for whiskers.
- Grasshoppers have hairs all over the outside of their bodies to detect air movement.
When a substance reacts chemically with the receptors of taste buds, the sensation of taste is created.
- People lose their perception of taste as they age. By age 20, half of their taste receptors are gone (on average).
- A snake has no taste buds on its tongue. It uses its tongue to bring smells and tastes into its mouth. Receptors in the pits of the snake’s mouth transmit the information to the brain.
- The catfish has about 100,000 taste buds (the average human has about 10,000 taste buds).
- A human’s taste sense interacts with other senses and factors, including smell, texture, and temperature.
- The five basic tastes are saltiness, sourness, sweetness, bitterness, and umami. The question is, how many tastes can a person really taste?
Last, but not least, is the good ol’ olfactory perception sense. Smell happens in humans when the brain receives signals after molecules in the air bind to sites on olfactory receptors.
- Every person smells things differently. This is because of the over 900,000 genetic variations of olfactory receptors. That lemon cake you smell and rave about to your friend? It might smell more like the inside of a shoe to your friend.
- Good smells make you happier!
- Dogs recognize and identify humans first by scent.
- Odors can accelerate puberty, attract mates, and alter menstrual cycles in humans.
- Grizzly bears can smell food from up to 18 miles away.