If I asked you to explain your sense of touch, you would probably describe it as the ability to feel things with your fingers. In reality, your sense of touch is much more.
The human body contains special nerve endings called sensory receptors that enable you to “feel” things. These receptors are not located only in your skin. They’re also found in muscles, joints, blood vessels and internal organs. Sensory receptors respond to light touch, pressure, stretching, warmth, cold, pain and vibration. Taken together, they make an arsenal of equipment that lets you react to both your inner world and the world around you.
The best way to identify something without looking at it is to use your fingers. Light touch and pressure receptors, which are located in the dermis, or middle layer of skin, are the ones that make this possible. These receptors are highly responsive to edges and fine details. Not surprisingly, you have more of them in your fingertips and lips than your arms and legs.
Hair does not contain nerve endings. However, hair follicles, which are located in the dermis, are surrounded by touch receptors. That’s why you can feel it if someone or something touches your hair. If it’s a friend stroking your ponytail, you’ll be pleased. If it’s bird poop dropping on it, you won’t.
Stretch receptors are located in your dermis, muscles and joints. Input from these sensors provides information that’s essential for gripping and releasing objects. When you throw a ball, you need to grab it hard enough so you don’t drop it, but you also need to release it carefully and at the right moment. If you didn’t know where your arms and joints were at any given moment, the ball could end up in someone’s gutter rather than a friend’s hands.
Stretch receptors in your lungs tell you when you’ve taken a full breath. The ones in your stomach help you recognise when you’re “full”. Stretch receptors in your rectum and bladder tell you when it’s time to visit the bathroom.
Pressure receptors in your arteries enable your brain to monitor and control your blood pressure.
Because you are endothermic (warm-blooded), the brain needs to monitor your core and skin temperature. Warmth and cold receptors are located in the dermis, skeletal muscles, liver and an area of the brain known as the hypothalamus. The hypothalamus controls many automatic bodily functions such as hunger, the fight-or-flight response and temperature regulation.
Receptors that transmit pain are located throughout the body. The ones that transmit superficial pain, such as a pinprick, are in the dermis. The purpose of pain is to let you know that something is wrong. If you didn’t realise that you stepped on a splinter, it could lead to a sore and an infection in your foot.
The brain does not contain pain nerves. If you have a headache, it’s not because your brain hurts. Rather, the pain is coming from the skull or internal structures that surround and support your brain. It might also be coming from the muscles in your scalp, the skin that covers your head. That’s especially true if you lie in strange positions while looking at your iPad.
— The Washington Post
