NervousSystemLab

DC Biology B Nervous System Lab Directions: Introduction: The human nervous system is composed of the brain and spinal cord and the nerves which branch out from the central nervous system, called the Peripheral Nervous System (PNS). Sensory neurons of the PNS carry information to the CNS. Signals from the brain are carried to motor neurons (PNS), which carry out responses by muscles. In this lab, you will be comparing the rate at which sensory neurons, working through the brain, can elicit responses via motor neurons. We will also be mapping out the density of sensory neurons on the skin as well as reaction time and how neurons work when cold. Purpose: To identify differences in the nervous system based on reaction response time and nerve density. Part 1: Reaction Time Part A—Arm and shoulder. For this lab, gather a meter stick and a family member or friend to help you conduct this experiment. Stand upright, with your arms extended straight out in front of the body, palms of the hands facing each other. The palms should be 10 cm apart. Place the meter stick exactly in the middle of the palms, with the 50 cm mark at the TOP of the index finger. The meter stick should be oriented so that “0” end is down and the “100” end is up. Have your family member or friend hold the top of the stick, and then let go (DO NOT LET THEM WARN YOU OR COUNT DOWN). The meter stick’s fall should be stopped by bringing your arms together to stop the fall of the meter stick. Have your helper ecord the distance that the stick fell by looking at the measurement lines on the meter stick that align with the index fingers as the palms hold the stick. Final position cm - 50.0 cm = Distance traveled Repeat this process three more times, recording your data in the table in this lab. Part B—Thumb and Index Finger. Stand upright, with your right arm extended straight out in front of the body, with the thumb and forefinger separated by 10 cm. As before, place the meter stick at the 50 cm mark between the finger and thumb, with the 50 cm mark aligned with the top of the index finger. Have your lab helper release the stick, and record the distance that the meter stick falls before you catch it. Repeat this process three more times, recording your data in the table in this lab.

Fall Distance in Centimeters (cm) Trial #1 Trial #2 Trial #3 Trial #4 Averag e Part A - Arm & Shoulder 42cm 20cm 25cm 26cm 28.25c m Part B - Thumb & Forefinger 27cm 24cm 19cm 22cm 23cm Part 2: Mapping Nerve Endings Obtain two straight pins from your parents. With these you will try to determine the distance between sensory neurons on several areas of the skin. You will also need a metric ruler. You will need a lab helper for this part as well. Have them sit in a chair with their eyes closed. Touch ( don’t poke ) the skin in each of the areas below with the two pins, beginning 1 cm apart. Only use the HEAD of the pins! Move the pin heads toward each other, lifting and touching each time, until your lab helper (eyes still closed) reports that they feel the sensation of only one pin touching them. Record the distance between the pins in millimeters at which the person can no longer distinguish that there are two pins touching them, and feel only one. Repeat this three more times for each area of the body that you are to test. Record your findings in the table below. Distance Between Pins, in Millimeters (mm) Trial #1 Trial #2 Trial #3 Trial #4 Averag e Pad of Right index finger 4mm 2mm 3mm 2mm 2.75mm Back of upper arm 7mm 6mm 4mm 5mm 5.75m m Back of neck 5mm 4.5mm 4mm 4mm 4.375m m Part 3: Temperature Effect on Neurons For this part of the lab, you will need a bowl of ice water and a large handful of pennies. You will get your hand wet and attempt to pick up as many pennies as you can in 30 seconds. You must pick them up from the desk with your fingertips, NOT slide them to the edge. You can only pick up one at a time. You should NOT have long finger nails. If you do, find a family member or friend to perform this experiment. Record the number below. Then have the same person immerse their hand in ice water for at least 1 minute 30 seconds. The sensations they feel