Why arent receptors evenly distributed

People who are blind use their fingertips to read Braille by feeling the patterns of raised dots on their paper. Per Student: 2 Chopsticks or unsharpened pencils.

Why are the fingertips more sensitive than the back? What are the 4 common skin receptors and why are they important?

What is the largest organ of the human body? Teacher tip: Demonstrate how students should be testing for tactile sensitivity before students try the activity. This activity is an accepted scientific test for skin sensitivity and is called a two point discrimination test. The distance between the two chopsticks is called the threshold distance and the closer they are when the student can still detect two chopsticks, the more sensitive the body part.

The receptors in our skin are not distributed in a uniform way around our bodies. Some places, such as our fingers and lips, have more touch receptors than other parts of our body, such as our backs. That is one reason why we are more sensitive to touch on our fingers and face than on our backs. The table below shows the varying sensitivity of our body parts. This data is from a two-point discrimination threshold experiment published in The Skin Senses, edited by D.

Kenshalo, Springfield, IL, Total time may be reduced if the number of skin areas tested are limited and if materials for "Try Your Own Experiment! Neuroscience Laboratory and Classroom Activities. Kandel, E. Principles of Neural Science. Fourth ed. Kiehle, C. Science Inquiry Tools for Middle Schools. Melzack, R. If so, you've probably noticed that some parts of your body are more ticklish than others.

That's because your skin's touch receptors aren't evenly distributed—some areas have more and others have a lot less. In this activity, you'll learn more about your sense of touch by testing your body's own reactions.

Background This activity is based on a physical exam used in medical checkups. Doctors use this test—called two-point discrimination—to study sensitivity on different parts of a patient's body.

This sensitivity is pretty important—without it you might not notice when your finger gets too close to a flame or when you've scraped your knee. Thanks to your skin receptors, you can feel a soft fleecy blanket, a cold splash of water or a sharp pinch—ouch! Skin receptors are actually tiny cells called sensory neurons. When your skin makes contact with something—say a fluffy bunny—sensory neurons receive that "fluffy" signal and send out their own signals that travel through your body to your brain, which puts them all together to recognize that you are feeling a fluffy bunny.

Both paper clip tips should touch the skin at the same time. Do you think your partner can feel both ends of the paper clip? If your partner feels only one point, bend the paper clip U a little bit wider and repeat. The smaller the distance, the more sensitive the area. Is your partner's sensitivity greater on the arm or elbow? Right or left hand? Palm or fingertip?