Anatomy & Physiology Fall 2004

SKIN SENSATIONS

WORKING WITH A PARTNER, PERFORM THE FOLLOWING EXPERIMENTS AND ANSWER THE ASSOCIATED QUESTIONS.

1. TWO - POINT DISCRIMINATION TEST

- THE DISTRIBUTION OF TACTILE (TOUCH) RECEPTORS VARIES OVER DIFFERENT AREAS OF THE BODY. WITH 2 CLEAN TOOTHPICK POINTS, TOUCH THE SKIN ON THE FOLLOWING SUGGESTED AREAS OF THE BODY. START WITH THE POINTS VERY CLOSE TOGETHER AND INCREASE THE DISTANCE BETWEEN THE POINTS UNTIL THE PERSON IS ABLE TO DISCERN TWO DISTINCT POINTS. BE SURE TO LIFT THE POINTS OFF THE SKIN WHEN INCREASING THE DISTANCE BETWEEN POINTS. RECORD THIS DISTANCE IN MILLIMETERS FOR EACH OF THE AREAS TESTED.

TIP OF NOSE __________________

BACK OF NECK ___________________

PALM OF HAND _______________

BACK OF HAND ____________________

WHAT CAN YOU CONCLUDE FROM THE ABOVE DATA?

2. ADAPTATION OF TOUCH RECEPTORS

- NOTE THE TIME ON A WATCH WITH A SECOND HAND, AND PLACE A COIN, SUCH AS A PENNY OR A DIME, UPON THE SKIN OF THE INSIDE OF THE FOREARM. HOW LONG DOES THE SENSATION LAST?

- THIS DISAPPEARANCE OF SENSATION IS DUE TO THE FACT THAT THE RECEPTORS ‘ADAPT’ TO THE PARTICULAR STIMULUS AND, THEREFORE, INITIATE NO MORE NERVE IMPULSES UNTIL A CHANGE TAKES PLACE IN THE STIMULUS. REPEAT THE EXPERIMENT ON A NEW SPOT ON THE SKIN, BUT AFTER THE SENSATION DISAPPEARS, ADD TWO MORE COINS OF THE SAME DENOMINATION ON TIP OF THE COIN, DID THE SENSATION RETURN?

HOW LONG DID THE SENSATION LAST WHEN 3 COINS WERE USED?