Reflexes and Reactions Lab

A reflex is an automatic response to a stimulus where your body acts before you think about it, thus the brain is not involved. For example, you smell a cake baking and your mouth salivates. On the other hand, a reaction does involve the CNS with the message being sent to the brain via motor neurons. The following activities will allow you to observe and analyze various reflexes and reactions.

Reflex Activities

Activity 1: Patellar Reflex

  1. The subject sits on a chair/desk/or table with the legsrelaxed and dangling.
  2. The observer locates the patella on the subject’s right leg
  3. The observer finds the patellar tendon just below the middle of the patella (it will feel soft in comparison to the patella)
  4. The observer uses the pointed end of the Taylorreflex hammer to tap the subject’s patellar tendon and observes the reflex.
  5. The subject notes the results on their data table
  6. The observer repeats the procedure, tapping the patellar tendon on the left leg.
  7. The subject notes the results on their data table.
  8. Switch roles until all group members are tested

Leg / Describe Results
Right
Left

How does the reflexes of your right and left leg compare?

Activity 2: Jendrassik’s Maneuver

  1. The subject sits on a chair/desk/or table the legs relaxed and dangling.
  2. The subject clasps hands with fingers locked in front of the body
  3. As the observer taps the right patellar tendon with the Taylor reflex hammer, the subject should simultaneously attempt to pull their hands apart
  4. The subject notes results on their data table
  5. The observer repeats the procedure, tapping on the patellar tendon of the left leg.
  6. The subject notes results on their data table
  7. Switch roles until all group members are tested

Leg / Describe Results
Right
Left

How did your reflex differ from Activity 1 to Activity 2?

Activity 3: Calcaneal Reflex

  1. The subject kneels on a chair or bench with feet dangling off the edge
  2. The observer uses the flat edge of the Taylor hammer to strike the subject’s right Achilles tendon right above the heel on the back of the leg
  3. The subject notes the results on their data sheet
  4. The subject reverses leg positions and slightly flexes the left foot. The observer strikes the subject’s left Achilles tendon right above the heel on the back of the leg
  5. The subject notes the results on their data sheet
  6. Switch roles until all group members are tested

Tendon / Describe Results
Right
Left

Absence of the calcaneal reflex may indicate damage to which region of the spinal cord?

Activity 4: Plantar Reflex

  1. The subject removes socks and shoes and extends their right foot toward the observer.
  2. The observer slides the handle of the Taylor reflex hammer along the bottom of the bare right foot from the heel up the lateral side of the foot and then across the ball of the foot to the big toe
  3. The subject notes the results on their data sheet
  4. The subject extends their bare left foot toward the observer and the observer repeats the test from #2
  5. The subject notes the results on their data sheet
  6. Switch roles until all group members are tested

Foot / Describe Results
Right
Left

Describe an abnormal plantar reflex. What does it signify?

Activity 5: Pupillary Reflex

  1. Obtain a metric ruler to measure the size of the subject’s pupil as best you can. The subject should record measurements on their data sheet

Right: ______mmLeft: ______mm

  1. Stand to the left of the subject to complete the testing. The subject should shield their right eye by holding a hand vertically between their eyes
  2. Shine a penlight into the subject’s left eye.
  3. Inform the subject of their response, they should record this on their data sheet
  4. Shine a penlight into the subject’s right eye
  5. Inform the subject of their response, they should record this on their data sheet
  6. Switch roles until all group members are tested

Eye / Describe Results
Right
Left

Why does pupil size change? What part of the eye accomplishes this change?

Activity 6: Ciliospinal Reflex

**If this activity makes you uncomfortable, you may work alone**

  1. The subject sits in a chair facing the observer
  2. While observing the subject’s left pupil, the observer either lightly runs a finger down the left side of the subject’s neck (right below the hairline) or LIGHTLY pinches the subject on the neck
  3. Inform the subject of their response, they should record this on their data sheet
  4. Switch roles until all group members are tested

What happened when the left side of your neck was touched or pinched?

Reaction Activities
Activity 7: Reaction Time Ruler

  1. The subject sits in a chair facing the observer
  2. The observer holds the ruler between the thumb and first finger by the end marked ‘release”
  3. The observer positions the ruler at the subject’s eye level or higher
  4. The subject places their thumb and first finger over the ‘thumb line’ leaving about 1 inch between the thumb and first finger. The subject should not be touching the ruler
  5. The observer releases the ruler and the subject catches it between their thumb and first finger
  6. The line under the subject’s thumb is time in milliseconds. Each line on the ruler represents 10 milliseconds. Estimate the reaction time.
  7. The subject should record their reaction time on their data table.
  8. Complete this test 10 times
  9. Switch roles until all group members are tested

Trial / Reaction Time (milliseconds)
1
2
3
4
5
6
7
8
9
10
Average

Did your reaction times differ as you performed more trials? If so, how?

Activity 8: Card Reaction Time

Trial 1:

  1. The subject holds a deck of shuffled playing cards face down
  2. The observer starts the clock and tells the subject to begin
  3. The subject turns over playing cards one at a time and places them in a ‘red’ pile and a ‘black’ pile. The subject continues until all cards have been placed
  4. Once all of the cards have been placed, the observer stops the timer and relays the time to the subject who records it on their data table.

Trial 2:

  1. The subject shuffles the cards used in trial 1 and the observer clears the timer
  2. The subject holds the shuffled cards face down
  3. The observer starts the timer and tells the subject to begin
  4. The subject turns over playing cards one at a time and separates them into four piles according to suit. The subject continues until all cards have been placed
  5. Once all of the cards have been placed, the observer stops the timer and relays the time to the subject who records it on their data table.
  6. The subject reshuffles the cards, clears the timer and the observer and subject switch places.

Trial / Reaction time (seconds)
1 (two piles)
2 (four piles)

How do you think your reaction times with the ruler and the cards be affected if you practiced every day for a week? Why?

How do you think that reaction time is affected by drinking caffeine? How do you think it’s affected by drinking alcohol?