Our body contains millions of nerve cells that respond directly to a given stimulus from the external environment. These nerve cells are also referred to as **sensory receptors**.

There are five known general groups of sensory receptors and they are the following:

1. Pain receptors – found in the damaged cells that detect *pain stimuli* associated with injury or disease.

2. Thermoreceptors – found in the skin and hypothalamus which function to detect the change in temperature.

3. Mechanoreceptors – found in the skin, skeletal muscles, and inner ears. These receptors respond to pressure, touch, and motion.

4. Chemoreceptors – found in our olfactory organ and taste buds of the tongue. These receptors detect chemical substances from the external environment usually associated with food and odor.

5. Photoreceptors – found in our eyes, that detect the presence or change of light.

– The **cornea** is very sensitive tissue that determines how much light enters the eye. If it is damaged and becomes opaque, the person might have difficulty with his vision.

– The **pupil** is the tiny black circle in our iris. It functions as a passageway of light to the retina.

– The **lens** is the structure found behind the iris. The lens together with the cornea aids to focus the light stimuli in the retina and helps our eyes to adjust their focus on near or distant objects.

– The **retina** contains numerous receptors cells found in the eye that sends nerve impulses to the brain via the optic nerve.

– The **optic nerve** is part of the peripheral nervous system that plays an important role in the creation of vision. This nerve transmits electrical signals from the eyes to the brain in order to process the information from the receptors.

**Taste buds** are specialized chemical receptors found on the tongue that distinguish the different tastes of the brain, sweet, sour, salty, and bitter. These receptors detect the different combinations of chemicals in the food and send these signals to the brain.

The inability to taste anything when you have a cold is intimately related to how we smell. Both taste and smell are results of perceptions of chemicals in the air or in the food we eat. The combination of our taste buds and the smell of food is what makes our brain recognize a taste.

When we have a cold, our nose gets clogged and we can’t smell as well as we normally can, so in our head, foods don’t taste the same because we’re not getting the normal amount of “taste information” from our nose”.

Because after you have stopped spinning, the fluids within the semicircular canals and sacs are still in motion, causing the person to still feel dizzy. once these fluids stop moving, then the person will stop feeling dizzy